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Väitekirja elektrooniline versioon ei sisalda publikatsioone, Neuraalsed adhesioonimolekulid (nCAM) ekspresseeruvad närvisüsteemis ning reguleerivad neuronitevaheliste ühenduste kujunemist sünnieelsest arengust kuni täiskasvanu eani. Käesolevas uurimuses keskendusime ülegenoomsetes uuringutes psühhiaatriliste häiretega seostatud IgLON perekonna adhesioonimolekulide uurimisele, täpsemalt LSAMP ja NEGR1 funktsiooni selgitamisele. Hiiremudelit kasutades leidsime, et nii LSAMP kui NEGR1 on ekspresseerunud serotonergilistes rakkudes. Serotonergilist närviülekannet võimendava SSRI estsitalopraami krooniline manustamine tingib nii Lsamp- kui Negr1-puudulikkusega hiirtel ajus monoamiinide profiili muutuse võrreldes nende metsiktüüpi pesakonnakaaslastega. Kui Lsamp välja lülitamise järgselt domineerib kõrgem serotoniini käive, siis Negr1-puudulikus hiires nägime muutusi esmajoones dopamiinisüsteemis. Lisaks esineb Negr1-puudulikkusega hiirtel süvenev käitumusliku sensitisatsiooni tõus amfetamiinile, ravimile, mis võimendab dopaminergilisi ja noradrenergilisi ajuprotsesse. Kroonilise amfetamiiniga kaasneb Negr1-puudulikkusega hiirtel ka tõusnud dopamiini vabanemine juttkehas. Kuna NEGR1 geen seostub GWAS uuringutes lisaks psühhiaatrilistele häiretele oluliselt ka kehamassi indeksiga, viisime Negr1-puudulikkusega hiirtel läbi põhjalikumad süsteemse metabolismi uuringud. Leidsime, et kuigi isased Negr1 puudulikkusega hiired söövad vähem nii tavatoitu kui kõrge rasvasisaldusega toitu, koguvad nad rasvarikka toiduga rohkem kehakaalu, neil tekib oluliselt raskem glükoosi tolerantsuse häire ning rasva kuhjumine maksa. Kokkuvõttes viitavad töö tulemused, et IgLON adhesioonivalkude mõju psühhiaatrilistele häiretele toimib vähemalt osaliselt läbi monoamiinergiliste ühenduste mõjutamise. Meie leid, et NEGR1 mõjutab lisaks aju biokeemiale ka süsteemset metabolismi, kinnitab, et psühhiaatrilisi sündroome võiks käsitleda kui kogu keha homöostaasi häireid., Neural cell adhesion molecules (nCAMs) are important in creating connections between neurons in the development of the nervous system, as well as in the adult brain. The current study focuses on the function on the IgLON nCAMs NEGR1 and LSAMP which have been linked with a variety of psychiatric conditions in genome-wide association studies. Using a mouse model, we found that both LSAMP and NEGR1 were expressed in serotonergic cells. Chronic administration of SSRI escitalopram, a drug that increases serotonergic neurotransmission, caused changes in the monoamine profile in the brains of both Lsamp- and Negr1-deficient mice compared to their wild-type littermates. While higher serotonin turnover was predominant in Lsamp-deficient mice, in Negr1-deficient mice we saw changes primarily in the dopamine system. In addition, Negr1-deficient mice showed a time-dependent increase in behavioural sensitization to amphetamine, a drug which increases on dopaminergic and noradrenergic neurotransmission. This sensitization was accompanied with higher dopamine release in the striatum of Negr1-deficient mice. As NEGR1 gene is also significantly associated with body mass index in addition to psychiatric disorders in GWAS studies, we studied systemic metabolism in Negr1-deficient mice. We found that although male Negr1-deficient mice eat less of both regular and high-fat food, they gain more body weight on high-fat food, develop a stronger impairment in glucose tolerance and have more fat accumulation in the liver. Taken together, the results indicate that the effect of IgLON adhesion proteins on psychiatric disorders is mediated at least partially by the regulation of monoaminergic circuits. Our finding that NEGR1 affects systemic metabolism in addition to brain biochemistry, confirms that psychiatric syndromes should be considered as disorders of homeostasis in the whole-body., https://www.ester.ee/record=b5539904

Includes supplementary materials for the online appendix. Cognitive-relevant information is processed by different brain areas that cooperate to eventually produce a response. The relationship between local activity and global brain states during such processes, however, remains for the most part unexplored. To address this question, we designed a simple face-recognition task performed in patients with drug-resistant epilepsy and monitored with intracranial electroencephalography (EEG). Based on our observations, we developed a novel analytical framework (named “local–global” framework) to statistically correlate the brain activity in every recorded gray-matter region with the widespread connectivity fluctuations as proxy to identify concurrent local activations and global brain phenomena that may plausibly reflect a common functional network during cognition. The application of the local–global framework to the data from three subjects showed that similar connectivity fluctuations found across patients were mainly coupled to the local activity of brain areas involved in face information processing. In particular, our findings provide preliminary evidence that the reported global measures might be a novel signature of functional brain activity reorganization when a stimulus is processed in a task context regardless of the specific recorded areas. We thank all subjects for their participation in the study. We also thank Rodrigo Quian Quiroga and Hernán G. Rey for sharing some of their code to design the task paradigm. MVV was supported by a fellowship from “la Caixa” Foundation, Spain (ID 100010434, fellowship code LCF/BQ/DE17/11600022). MVV and ATC were supported by the Bial Foundation grant 106/18. GD, ATC and MVV were supported by the project “Clúster Emergent del Cervell Humà” (CECH, ref. 001-P-001682), within the framework of the European Research Development Fund Operational Program of Catalonia 2014–2020. ATC was supported by the Spanish National Research project (ref. PID2020-119072RA-I00/AEI/10.13039/501100011033) funded by the Spanish Ministry of Science, Innovation, and Universities (MCIU). GD was supported by a Spanish National Research project (ref. PID2019-105772GB-I00 MCIU AEI) funded by the Spanish Ministry of Science, Innovation, and Universities (MCIU), State Research Agency (AEI); HBP SGA3 Human Brain Project Specific Grant Agreement 3 (grant agreement no. 945539), funded by the EU H2020 FET Flagship programme; SGR Research Support Group support (ref. 2017 SGR 1545), funded by the Catalan Agency for Management of University and Research Grants (AGAUR); Neurotwin Digital twins for model-driven noninvasive electrical brain stimulation (grant agreement ID: 101017716) funded by the EU H2020 FET Proactive programme; euSNN European School of Network Neuroscience (grant agreement ID: 860563) funded by the EU H2020 MSCA-ITN Innovative Training Networks; Brain-Connects: Brain Connectivity during Stroke Recovery and Rehabilitation (ID 201725.33) funded by the Fundacio La Marato TV3; Corticity, FLAG-ERA JTC 2017 (ref. PCI2018-092891) funded by the Spanish Ministry of Science, Innovation and Universities (MCIU), State Research Agency (AEI). This research was also supported by “la Caixa” Foundation (CaixaImpulse Validate Program, project ref. CI20-00195).

γ-Aminobutyric acid type-A receptors (GABAARs) play a critical role in neural transmission by mediating the inhibitory neural firing and are the target of many psychiatric drugs. Among them, propofol is one of the most widely used and important general anesthetics in clinics. Recent advances in structural biology revealed the structure of a human GABAAR in both open and closed states. Yet, the detailed mechanism of the receptor and propofol remains to be fully understood. Therefore, in this study, based on the previous successes in structural biology, a variety of computational techniques were applied to fill the gap between previous experimental studies. This study investigated the ion-conducting mechanism of GABAAR, predicted the possible binding mechanism of propofol, and revealed a new motion mechanism of transmembrane domain (TMD) helices. We hope that this study may contribute to future studies on ion-channel receptors, general anesthetics, and drug development.

[eng] Synapses are the contact sites where the transfer of information from the presynaptic to the postsynaptic site occurs. Correct processing of information requires that synapses continuously adapt their properties to an ever-changing environment. Here, we describe novel aspects that help understand the function of presynaptic terminals in the context of a simple neuronal network. The exuberant number of synaptic contacts formed during the development of the nervous system is selectively refined by a process of synapse elimination. In the current thesis we have exploited the action of peptide p4.2, a 20 amino acid fragment located in the C-terminus of the glial secreted protein SPARC, which promotes synapse elimination in an autaptic circuit. We found that neurons forming autaptic synapses sense and compensate for synapse elimination by activating a mechanism of presynaptic homeostatic plasticity driven by presynaptic potentiation and rapid assembly of new synaptic contacts. Both actions occur concomitantly, indicating that the formation of novel synapses is associated to an overall increase in presynaptic calcium influx. To further investigate the molecular mechanisms underlying this compensatory response, we moved our interests to the participation of microtubules in the maintenance of synaptic connectivity and synaptic strength. This question could only be addressed by gaining a better understanding of the participation of microtubules in presynaptic terminal function. By providing ultrastructural, morphological, and physiological evidence we have shown that microtubule plus-ends transiently invade presynaptic boutons and that microtubule instability is directly involved in the regulation of spontaneous neurotransmitter release probability. Microtubule polymerization is also important to postsynaptic function, indicating microtubule dynamics might be involved in forms of postsynaptic plasticity. Altogether, the development of this project has allowed to identify yet unknown mechanisms key for better understanding the cell biology of presynaptic terminals. These findings should not only be considered in the context of a simple neuronal network, chosen because of its unique experimental possibilities, but as fundamental neuronal properties. Yet, future research in complex systems are required to further validate our findings., [spa] Las sinapsis son los sitios de contacto donde ocurre la transferencia de información desde el terminal presináptico al postsináptico. El correcto procesamiento de información requiere que las sinapsis adapten continuamente sus propiedades bajo un entorno de constante cambio. En esta tesis describimos aspectos novedosos que ayudan a comprender la función de los terminales presinápticos en el contexto de una red neuronal simple. El número exuberante de contactos sinápticos formados durante el desarrollo del sistema nervioso se refina selectivamente mediante un proceso de eliminación sináptica. En la presente tesis hemos explotado la acción del péptido p4.2, un fragmento de 20 aminoácidos situado en el extremo C-terminal de la proteína de secreción glial SPARC, que promueve la eliminación de sinapsis en un circuito autáptico. Hemos descubierto que las neuronas que forman sinapsis autápticas detectan y compensan la eliminación sináptica activando un mecanismo de plasticidad homeostática presináptica impulsado por la potenciación presináptica y el rápido ensamblaje de nuevos contactos sinápticos. Ambas acciones ocurren de manera concomitante, lo que indica que la formación de nuevas sinapsis está asociada con un aumento general en el flujo de entrada de calcio presináptico. Para investigar más a fondo los mecanismos moleculares que subyacen a esta respuesta compensatoria, trasladamos nuestro foco de investigación a la participación de los microtúbulos en el mantenimiento de la conectividad y fuerza sináptica. Proporcionando evidencia ultraestructural, morfológica y fisiológica, hemos demostrado que los extremos positivos de los microtúbulos invaden transitoriamente los botones presinápticos y que la inestabilidad de los microtúbulos está directamente involucrada en la regulación de la probabilidad de liberación espontánea de neurotransmisores. La polimerización de microtúbulos también es importante para la función postsináptica, lo que indica que la dinámica de los microtúbulos podría estar involucrada en formas de plasticidad postsináptica. El desarrollo de este proyecto ha permitido identificar mecanismos aún desconocidos que son clave para entender la biología celular de los terminales presinápticos. Estos hallazgos no solo deben considerarse en el contexto de una red neuronal simple, elegida por sus posibilidades experimentales únicas, sino como propiedades neuronales fundamentales. Sin embargo, futuras investigaciones en sistemas complejos son necesarias para validar nuestros hallazgos.

The development of local anesthetic (LA) system is the application of commercial drug for the pain management that indorses the reversible obstructive mechanism of neural transmission through preventing the innervation process in human peripheral nerves. Ropivacaine (RV) is one of the greatest frequently used LA s with the actions of long-lasting and low-toxicity for the post-operative pain management. In this work, we have approached novel design and development of glycosylated chitosan (GCS) encapsulated mesoporous silica nanoparticles (GCS-MONPs)-based nano-scaffold for sustainable distributions and controlled/supported arrival of stacked RV for targeting sites, which can be activated by either outer ultrasound activating to discharge the payload, foundation on-request and dependable analgesia. The structural and morphology analyses result established that prepared nano-formulations have successful molecular interactions and RV loaded spherical morphological structures. The drug release profile of developed nanostructure with ultrasound-activation has been achieved 50% of drug release in 2 h and 90% of drug release was achieved in 12 h, which displays more controlled release when compared to free RV solution. The in vitro cell compatibility analysis exhibited GCS-MONPs with RV has improved neuron cell survival rates when compared to other samples due to its porous surface and suitable biopolymer proportions. The analysis of ex vitro and in vivo pain relief analysis demonstrated treated animal models have high compatibility with GCS-MONPs@RV, which was confirmed by histomorphology. This developed MONPs based formulations with ultrasound-irradiation gives a prospective technique to clinical agony the board through on-request and dependable help with discomfort.

The development of an organism from an undifferentiated single cell into a spatially complex structure requires spatial patterning of cell fates across tissues. Positional information, proposed by Lewis Wolpert in 1969, has led to the characterization of many components involved in regulating morphogen signaling activity. However, how morphogen gradients are established, maintained, and interpreted by cells still is not fully understood. Quantitative and systems-based approaches are increasingly needed to define general biological design rules that govern positional information systems in developing organisms. This short review highlights a selective set of studies that have investigated the roles of physiological signaling in modulating and mediating morphogen-based pattern formation. Similarities between neural transmission and morphogen-based pattern formation mechanisms suggest underlying shared principles of active cell-based communication. Within larger tissues, neural networks provide directed information, via physiological signaling, that supplements positional information through diffusion. Further, mounting evidence demonstrates that physiological signaling plays a role in ensuring robustness of morphogen-based signaling. We conclude by highlighting several outstanding questions regarding the role of physiological signaling in morphogen-based pattern formation. Elucidating how physiological signaling impacts positional information is critical for understanding the close coupling of developmental and cellular processes in the context of development, disease, and regeneration.

Background A coral colony is composed of physiologically integrated polyps. In stony corals, coloniality adopts a wide diversity of forms and involves complex ontogenetic dynamics. However, molecular mechanisms underlying coloniality have been little studied. To understand the genetic basis of coloniality and its contribution to coral ecology, we induced polyp bail-out in a colonial coral, Pocillopora acuta, and compared transcription profiles of bailed-out polyps and polyps in normal colonies, and their responses to heat shock and hyposalinity. Results Consistent with morphological formation of a gastrovascular system and its neural transmission and molecular transport functions, we found genetic activation of neurogenesis and development of tube-like structures in normal colonies that is absent in bailed-out polyps. Moreover, relative to bailed-out polyps, colonies showed significant overexpression of genes for angiotensin-converting enzymes and endothelin-converting enzymes. In response to hyperthermal and hyposaline treatments, a high proportion of genetic regulation proved specific to either bailed-out polyps or colonies. Elevated temperatures even activated NF-κB signaling in colonies. On the other hand, colonies showed no discernible advantage over bailed-out polyps in regard to hyposalinity. Conclusions The present study provides a first look at the genetic basis of coloniality and documents different responses to environmental stimuli in P. acuta colonies versus those in bailed-out polyps. Overexpression of angiotensin-converting enzymes and endothelin-converting enzymes in colonies suggests possible involvement of these genes in development of the gastrovascular system in P. acuta. Functional characterization of these coral genes and further investigation of other forms of the transition to coloniality in stony corals should be fruitful areas for future research.

Cannabinoids, the bioactive constituents of cannabis, exert a wide array of effects on the brain by engaging Type 1 cannabinoid receptor (CB1R). Accruing evidence supports that cannabinoid action relies on context-dependent factors, such as the biological characteristics of the target cell, suggesting that cell population-intrinsic molecular cues modulate CB1R-dependent signaling. Here, by using a yeast two-hybrid-based high-throughput screening, we identified BiP as a potential CB1R-interacting protein. We next found that CB1R and BiP interact specifically in vitro, and mapped the interaction site within the CB1R C-terminal (intracellular) domain and the BiP C-terminal (substrate-binding) domain-a. BiP selectively shaped agonist-evoked CB1R signaling by blocking an "alternative" Gq/11 protein-dependent signaling module while leaving the "classical" Gi/o protein-dependent inhibition of the cAMP pathway unaffected. In situ proximity ligation assays conducted on brain samples from various genetic mouse models of conditional loss or gain of CB1R expression allowed to map CB1R-BiP complexes selectively on terminals of GABAergic neurons. Behavioral studies using cannabinoid- treated male BiP1/2 mice supported that CB1R-BiP complexes modulate cannabinoid-evoked anxiety, one of the most frequent undesired effects of cannabis. Together, by identifying BiP as a CB1R-interacting protein that controls receptor function in a signaling pathway- and neuron population-selective manner, our findings may help to understand the striking context-dependent actions of cannabis in the brain., This work was supported by Spanish Ministerio de Ciencia e Innovación Grants RTI2018-095311-B-I00 to M.G., SAF-2017-87629-R to E.I.C. and V.C., PID2019-106404RB-I00 to L.U., BFU 2017-83292-R to J.S.-P., and RTI2018-094374-B-I00 to S.G.; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas Grant PI2018/01 to M.G., S.G., and G. Mengod; and UK Research and Innovation Biotechnology and Biological Sciences Research Council Grant BB/R006946/1 to P.J.M., L.B., and G. Marsicano were supported by Institut National de la Santé et de la Recherche Médicale. C.C.-I. and I.B.M. were supported by contracts from Spanish Ministerio de Universidades (Formación de Profesorado Universitario Program, references FPU16/02593 and FPU15/01833, respectively). R.B.-G. was supported by a contract from Spanish Ministerio de Ciencia e Innovación Juan de la Cierva Program.

Amyloid precursor protein (APP) is a type 1 transmembrane glycoprotein, and its homologs amyloid precursor-like protein 1 (APLP1) and amyloid precursor-like protein 2 (APLP2) are highly conserved in mammals. APP and APLP are known to be intimately involved in the pathogenesis and progression of Alzheimer’s disease and to play important roles in neuronal homeostasis and development and neural transmission. APP and APLP are also expressed in non-neuronal tissues and are overexpressed in cancer cells. Furthermore, research indicates they are involved in several cancers. In this review, we examine the biological characteristics of APP-related family members and their roles in cancer.

Studies of circadian locomotor rhythms inDrosophila melanogastergave evidence to the preceding theoretical predictions on circadian rhythms. The molecular oscillator in flies, as in virtually all organisms, operates using transcriptional-translational feedback loops together with intricate post-transcriptional processes. Approximately150 pacemaker neurons, each equipped with a molecular oscillator, form a circuit that functions as the central pacemaker for locomotor rhythms. Input and output pathways to and from the pacemaker circuit are dissected to the level of individual neurons. Pacemaker neurons consist of functionally diverse subclasses, including those designated as the Morning/Master (M)-oscillator essential for driving free-running locomotor rhythms in constant darkness and the Evening (E)-oscillator that drives evening activity. However, accumulating evidence challenges this dual-oscillator model for the circadian circuit organization and propose the view that multiple oscillators are coordinated through network interactions. Here we attempt to provide further evidence to the revised model of the circadian network. We demonstrate that the disruption of molecular clocks or neural output of the M-oscillator during adulthood dampens free-running behavior surprisingly slowly, whereas the disruption of both functions results in an immediate arrhythmia. Therefore, clocks and neural communication of the M-oscillator act additively to sustain rhythmic locomotor output. This phenomenon also suggests that M-oscillator can be a pacemaker or a downstream path that passively receives rhythmic inputs from another pacemaker and convey output signals. Our results support the distributed network model and highlight the remarkable resilience of theDrosophilacircadian pacemaker circuit, which can alter its topology to maintain locomotor rhythms.

Membrane proteins (MPs) influence all aspects of life, such as tumorigenesis, immune response, and neural transmission. However, characterization of MPs is challenging, as it often needs highly specialized techniques inaccessible to many labs. We herein introduce nanodisc-ID that enables quantitative analysis of membrane proteins using a gel electrophoresis readout. By leveraging the power of nanodiscs and proximity labeling, nanodisc-ID serves both as scaffolds for encasing biochemical reactions and as sensitive reagents for detecting membrane protein-lipid and protein-protein interactions. We demonstrate this label-free and low-cost tool by characterizing a wide range of integral and peripheral membrane proteins from prokaryotes and eukaryotes., Huan Bao describes nanodisc-ID which leverages nanodisc with proximity labeling, for the detection of membrane protein-lipid and protein-protein interactions. Its utility is demonstrated by characterising a wide range of integral and peripheral membrane proteins from prokaryotes and eukaryotes.

A major cause of human blindness is the death of rod photoreceptors. As rods degenerate, synaptic structures between rod and rod bipolar cells disappear and the rod bipolar cells extend their dendrites and occasionally make aberrant contacts. Such changes are broadly observed in blinding disorders caused by photoreceptor cell death and are thought to occur in response to deafferentation. How the remodeled retinal circuit affects visual processing following rod rescue is not known. To address this question, we generated male and female transgenic mice wherein a disrupted cGMP-gated channel (CNG) gene can be repaired at the endogenous locus and at different stages of degeneration by tamoxifen-inducible cre-mediated recombination. In normal rods, light-induced closure of CNG channels leads to hyperpolarization of the cell, reducing neurotransmitter release at the synapse. Similarly, rods lacking CNG channels exhibit a resting membrane potential that was ~10 mV hyperpolarized compared to WT rods, indicating diminished glutamate release. Retinas from these mice undergo stereotypic retinal remodeling as a consequence of rod malfunction and degeneration. Upon tamoxifen-induced expression of CNG channels, rods recovered their structure and exhibited normal light responses. Moreover, we show that the adult mouse retina displays a surprising degree of plasticity upon activation of rod input. Wayward bipolar cell dendrites establish contact with rods to support normal synaptic transmission, which is propagated to the retinal ganglion cells. These findings demonstrate remarkable plasticity extending beyond the developmental period and support efforts to repair or replace defective rods in patients blinded by rod degeneration. SIGNIFICANCE STATEMENT Current strategies for treatment of neurodegenerative disorders are focused on the repair of the primary affected cell type. However, the defective neurons function within a complex neural circuitry, which also becomes degraded during disease. It is not known whether rescued neurons and the remodeled circuit will establish communication to regain normal function. We show that the adult mammalian neural retina exhibits a surprising degree of plasticity following rescue of rod photoreceptors. The wayward dendrites of rod bipolar cells re-establish contact with rods to support normal synaptic transmission, which is propagated to the retinal ganglion cells. These findings support efforts to repair or replace defective rods in patients blinded by rod cell loss.

Objectives Although children with unilateral hearing loss (uHL) have high risk of experiencing academic difficulties, speech-language delays, poor sound localization, and speech recognition in noise, studies on hearing aid (HA) outcomes are few. Consequently, it is unknown when and how amplification is optimally provided. The aim was to study whether children with mild-to-moderate congenital unilateral sensorineural hearing loss (uSNHL) benefit from HAs. Design All 6- to 11-year-old children with nonsyndromic congenital uSNHL and at least 6 months of HA use were invited (born in Stockholm county council, n = 7). Participants were 6 children (9.7- to 10.8-years-old) with late HA fittings (>4.8 years of age). Unaided and aided hearing was studied with a comprehensive test battery in a within-subject design. Questionnaires were used to study overall hearing performance and disability. Sound localization accuracy (SLA) and speech recognition thresholds (SRTs) in competing speech were measured in sound field to study hearing under demanding listening conditions. SLA was measured by recording eye-gaze in response to auditory-visual stimuli presented from 12 loudspeaker-video display pairs arranged equidistantly within ±55° in the frontal horizontal plane. The SRTs were measured for target sentences at 0° in spatially separated (±30° and ±150°) continuous speech. Auditory brainstem responses (ABRs) were obtained in both ears separately to study auditory nerve function at the brainstem level. Results The mean ± SD pure-tone average (0.5, 1, 2, and 4 kHz) was 45 ± 8 dB HL and 6 ± 4 dB HL in the impaired and normal hearing ear, respectively (n = 6). Horizontal SLA was significantly poorer in the aided compared with unaided condition. A significant relationship was found between aided SLA (quantified by an error index) and the impaired ear's ABR I to V interval, suggesting a relationship between the two. Results from questionnaires revealed aided benefit in one-to-one communication, whereas no significant benefit was found for communication in background noise or reverberation. No aided benefit was found for the SRTs in competing speech. Conclusions Children with congenital uSNHL benefit from late HA intervention in one-to-one communication but not in demanding listening situations, and there is a risk of degraded SLA. The results indicate that neural transmission time from the impaired cochlea to the upper brainstem may have an important role in unilaterally aided spatial hearing, warranting further study in children with uHL receiving early HA intervention.

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In everyday life multisensory events, such as a glass crashing on the floor, the different sensory inputs are often experienced as simultaneous, despite the sensory processing of sound and sight within the brain are temporally misaligned. This lack of cross-modal synchrony is the unavoidable consequence of different light and sound speeds, and their different neural transmission times in the corresponding sensory pathways. Hence, cross-modal synchrony must be reconstructed during perception. It has been suggested that spontaneous fluctuations in neural excitability might be involved in the temporal organisation of sensory events during perception and account for variability in behavioural performance. Here, we addressed the relationship between ongoing brain oscillations and the perception of cross-modal simultaneity. Participants performed an audio-visual simultaneity judgement task while their EEG was recorded. We focused on pre-stimulu activity, and found that the phase of neural oscillations at 13 ± 2 Hz 200 ms prior to the stimulus correlated with subjective simultaneity of otherwise identical sound-flash events. Remarkably, the correlation between EEG phase and behavioural report occurred in the absence of concomitant changes in EEG amplitude. The probability of simultaneity perception fluctuated significantly as a function of pre-stimulus phase, with the largest perceptual variation being accounted for phase angles nearly 180º apart. This pattern was strongly reliable for sound-flash pairs but not for flash-sound pairs. Overall, these findings suggest that the phase of ongoing brain activity might underlie internal states of the observer that influence cross-modal temporal organisation between the senses and, in turn, subjective synchrony.

[spa] Las sinucleínas son una familia de proteínas pequeñas y altamente conservadas en vertebrados, especialmente abundantes en las neuronas y típicamente enriquecidas en los terminales presinápticos, donde participan en la homeostasis y el mantenimiento de la función sináptica. Entre ellas, α- y γ-sinucleína (α-Syn y γ-Syn) se expresan de modo abundante en los núcleos monoaminérgicos del cerebro y modulan varios componentes de la neurotransmisión, por lo que constituyen dianas moleculares de alto interés en las enfermedades neuropsiquiátricas y neurodegenerativas. Gran cantidad de evidencias vinculan a la proteína α-Syn con la enfermedad de Parkinson (PD), incluyendo la presencia de agregados proteicos insolubles que contienen la forma fosforilada de α-Syn, así como mutaciones en el gen que codifica para α-Syn. Sin embargo, se conoce menos acerca de la γ-Syn, que también se ha visto implicada en la fisiopatología de enfermedades neurodegenerativas y varias sinucleinopatías. La presente tesis se ha centrado en el estudio de la distribución y localización celular de γ-Syn en el cerebro de ratón, así como el papel fisiológico de la misma en la regulación de la neurotransmisión dopaminérgica (DA). Para ello se utilizaron dos modelos murinos diferentes, con: 1) sobreexpresión de γ-Syn en las neuronas DA de la substantia nigra compacta / área tegemental ventral (SNc/VTA) usando un vector adenoasociado con promotor de citomegalovirus (AAV10-CMV-mouse-γ-Syn), y 2) expresión reducida (knockdown) de γ-Syn en las neuronas DA de SNc/VTA, inducida por oligonucleótidos inhibitorios (siRNA y ASO). Además, también se examinó si la terapia no viral basada en un oligonucleótido antisentido contra α-Syn conjugado con indatralina (IND-1233-ASO), previamente evaluado en ratones normales y en monos envejecidos, es eficaz en modelos murinos transgénicos de PD portadores de formas mutadas del gen SNCA (αSyn*A30P*A53T) y LRRK2 (LRRK2*G2019S). γ-Syn se ha caracterizado expresándose selectivamente en los núcleos monoaminérgicos del cerebro de ratón: SNc/VTA, núcleos del rafe (DR) y locus coeruleus (LC), así como en los núcleos de la habénula. Mediante la sobreexpresión por AAV10 se han conseguido duplicar de manera estable los niveles de γ-Syn en la SNc/VTA. El silenciamiento por la aplicación local de un ASO conjugado con indatralina ha reducido un 20-25% la expresión de γ-Syn en la SNc/VTA, mientras que la administración intracerebroventricular ha reducido sus niveles un 40% en los núcleos monoaminérgicos. Mediante ambos modelos se ha demostrado que γ-Syn modula negativamente la liberación de DA y la función de recaptación del transportador de DA en la neurotransmisión nigroestriatal y mesocortical. Además, los ratones con sobreexpresión de γ-Syn mostraron alteraciones en la coordinación motora, la memoria a corto plazo y el aprendizaje. Los ratones transgénicos αSyn*A30P*A53T mostraron incrementos de la forma humana de α-Syn en la SNc/VTA y el LC, con niveles 3-4 veces superiores a la α-Syn endógena. Paralelamente, los ratones presentaron una menor liberación sináptica de DA en el cuerpo estriado y un mayor aumento de DA frente a la infusión de anfetamina; además, los ratones transgénicos mostraron una menor actividad locomotora y un comportamiento de tipo ansioso. La administración intracerebroventricular de IND-1233-ASO durante 28 días redujo la expresión de la forma humana de α-Syn un 40%, dejando una mejoría en las alteraciones de la neurotransmisión DA, pero no sobre los déficits conductuales. En el modelo LRRK2*G2019S, los ratones presentaron un ligero aumento de la expresión de α-Syn en la SNc/VTA; además, también se detectó una mayor recaptación de DA estriatal y defectos en la memoria a corto plazo. La administración sostenida de IND-1233-ASO durante 28 días no fue capaz de disminuir la expresión de α-Syn en la SNc/VTA de los ratones LRRK2*G2019S.

Efficient neural transmission is crucial for optimal brain function, yet the plastic potential of white matter (WM) has long been overlooked. Growing evidence now shows that modifications to axons and myelin occur not only as a result of long-term learning, but also after short training periods. Motor sequence learning (MSL), a common paradigm used to study neuroplasticity, occurs in overlapping learning stages and different neural circuits are involved in each stage. However, most studies investigating short-term WM plasticity have used a pre-post design, in which the temporal dynamics of changes across learning stages cannot be assessed. In this study, we used multiple magnetic resonance imaging (MRI) scans at 7 Tesla to investigate changes in WM in a group learning a complex visuomotor sequence (LRN) and in a control group (SMP) performing a simple sequence, for 5 consecutive days. Consistent with behavioral results, where most improvements occurred between the two first days, structural changes in WM were observed only in the early phase of learning (d1-d2), and in overall learning (d1-d5). In LRNs, WM microstructure was altered in the tracts underlying the primary motor and sensorimotor cortices. Moreover, our structural findings in WM were related to changes in functional connectivity, assessed with resting-state functional MRI data in the same cohort, through analyses in regions of interest (ROIs). Significant changes in WM microstructure were found in a ROI underlying the right supplementary motor area. Together, our findings provide evidence for highly dynamic WM plasticity in the sensorimotor network during short-term MSL.

[eng] Light-controlled manipulation of neuronal activity has transformed the field of neurobiology. Light provides temporal and spatial resolution over activation or inhibition of targeted populations of neurons, one single neuron or single synapses. Such precision could be achieved with optogenetics, which is based on the over-expression of light-sensitive proteins, but it requires gene therapy and often alters cellular physiology. An alternative to optogenetics is offered by photopharmacology (the development of light-regulated drugs or photoswitches), which can operate on endogenous receptors without genetic manipulation. Several new photoswitches are described in this thesis to improve their pharmacological and optical properties. In photopharmacology, azobenzene is the most commonly used light switch. Photoswitchable tethered ligands (PTLs) are tri-modular molecules able to anchor to target receptors and alter their function by switching the azobenzene group. In the first chapter we demonstrate the ability to target endogenous receptors of hippocampal neurons and olfactory bulb neurons from Xenopus larvae. The chemical strategy used was to introduce a highly reactive anchoring group to a PTL with similar structure to the reported MAG compound used in the light regulated glutamate receptor, LiGluR. These new kind of PTLs were called “Targeted Covalent Photoswitches” (TCPs). The promiscuity of the reactive group of TCP limits the possibility to spatially confine the drug conjugation. Thus, we designed a photolabile TCP that can be conjugated to its target with a specific wavelength, and then be photoswitched at another wavelength. Despite the advantages of all molecules described above, they share a common limitation: the activation wavelength of azobenzene is in the UV-violet range. Increasing the push-pull effect at the azobenzenic core by adding different substituents, we achieved a TCP derivative activatable at the visible range and ultrafast relaxing. In this way a single wavelength of stimulation can be used. Both features make them great candidates to control ultrafast neurotransmission processes such as the ones implicated in sound coding in the cochlea. We demonstrated in a gerbil animal model the capacity of this blue-activated TCP to photosensitize native receptors of adult gerbil cochlea. This first proof of concept opens new possibilities to develop optical cochlear implants for the treatment of hearing loss avoiding gene therapy. Chemical substitutions can also be rationally designed to enhance two-photon (2P) absorptivity without modifying the dynamics of photoswitches. In the third chapter we described two new 2P enhanced MAG derivatives to photocontrol LiGluR. We validated their properties with an all-optical approach, by recording calcium induced neuronal responses in organotypic hippocampal slices, and in vivo in Caenorhabditis elegans. The combination of slow relaxation lifetime and enhanced 2P absorptivity is translated into an accumulation of the active isomer of the photoswitch that successfully enhances its functional effect even at low illumination power. Another way to spectrally modify the characteristics of a chromophore while avoiding mutation screening and new synthetic processes is by using light-harvesting fluorophores. Spectral overlapping of fluorophore emission and chromophore absorption broadens its activation spectrum. By means of chemical protection and deprotection, we orthogonally control the conjugation of fluorophores and photoswitches. This is the first demonstration of light-harvesting strategy for optogenetics and photopharmacology. Finally, we describe the use of novel PCLs containing chromophores other than linear azobenzene for the light-controlled activation of hippocampal neurons. Cyclic azobenzenes reverse isomer thermal stability and consequently also the activity of the photoswitch. On the other hand, stilbenes allow the irreversible but non-photo-destructive activation of the original molecule, thus avoiding the creation of photo-products. In conclusion, this thesis puts forward several advances in the photochromism and pharmacology of photoswitches for the control of neurotransmission without need of genetic manipulation., [cat] L'estudi electrofisiològic i d’imatge de l’activitat neuronal en temps real requereix una gran resolució espacial i temporal. Ambdós trets es poden aconseguir amb la precisió, velocitat i control remot que permet la llum. En aquesta tesi es descriu la caracterització de nous fotocommutadors dirigits a fotosensibilitzar receptors endògens de glutamat i estratègies per la millora de les seves característiques òptiques. Els primers fotoconmutadors descrits capaços de controlar amb llum l’activitat de canals endògens de glutamat son eficaços en altres aproximacions experimentals com ara en la inducció amb llum de potencials d’acció en neurones en cultiu, en cultius organotípics d’hipocamp de rata o in vivo en larves de Xenopus electroporades, a nivell d’un grup neuronal, d’una única neurona o d’una única espina sinàptica. Modificant la part reactiva del fotocommutador, som podem controlar espacialment la conjugació mitjançant patrons d’il·luminació. Canviant l’estructura química s’aconsegueix un fotocommutador actiu en el rang visible de llum i alhora extremadament ràpid. Fet que el fa ideal pel control de sinapsis ultra ràpides com ara les encarregades de codificar el so en la còclea. El disseny racional d’altres modificacions químiques en fotocommutadors de receptors de glutamat (LiGluRs) obre les portes al disseny de molècules sensibles a l’activació per 2 fotons. L’estimulació de 2 fotons amb làsers polsats de llum infraroja comporta importants avantatges com ara l’augment de la capacitat de penetració en teixit i una disminució de possibles danys degut a una sobreexposició a la llum. Característiques molt útils per estudis in vivo. Modificacions químiques dels fotocommutadors comporten altres modificacions en les seves característiques fotodinàmiques. Per aquest motiu, hem desenvolupat una estratègia de conjugació de fluoròfors col·lectors de llum que mitjançant RET transfereixen la seva energia al cromòfor (fotocommutador), modificant-ne les característiques espectrals. Es demostra que cromòfors no conjugables permeten controlar l’activitat neuronal. Amb diversos avantatges respecte l’azobenzè clàssic: els azobenzens cíclics reverteix l’estabilitat i en conseqüència l’activitat de la molècula; i els estilbens permeten l’activació irreversible però no foto-destructiva de la molècula original, evitant així la creació de foto-productes. En conclusió, en aquesta tesi es presenten noves molècules i estratègies de disseny per al control de la neurotransmissió sense necessitat de modificacions genètiques.

Summary Kainate receptors (KARs) mediate postsynaptic currents with a key impact on neuronal excitability. However, the molecular determinants controlling KAR postsynaptic localization and stabilization are poorly understood. Here, we exploit optogenetic and single-particle tracking approaches to study the role of KAR conformational states induced by glutamate binding on KAR lateral mobility at synapses. We report that following glutamate binding, KARs are readily and reversibly trapped at glutamatergic synapses through increased interaction with the β-catenin/N-cadherin complex. We demonstrate that such activation-dependent synaptic immobilization of KARs is crucial for the modulation of short-term plasticity of glutamatergic synapses. Thus, the present study unveils the crosstalk between conformational states and lateral mobility of KARs, a mechanism regulating glutamatergic signaling, particularly in conditions of sustained synaptic activity., Graphical Abstract, Highlights • Anchoring of KARs at glutamatergic synapses depends on receptor-glutamate binding • KARs activation/desensitization promotes receptors trapping at glutamatergic synapses • N-cadherins mediate the KAR activation/desensitization-dependent anchoring at synapses • Synaptic trapping of desensitized KARs affects short-term synaptic plasticity, Polenghi et al. report that following their activation, kainate receptors (KARs) are readily trapped at glutamatergic synapses in the open/desensitized state. This mechanism defines the number of ready-to-be-activated KARs at synapses, with direct impacts on short-term synaptic plasticity.

[cat] La neurotransmissió és el procés funcional bàsic de comunicació neuronal, i té lloc a través de l’alliberament dels neurotransmissors a l’espai sinàptic. Els defectes clàssics monogènics dels neurotransmissors inclouen els trastorns del metabolisme, degradació i transport de les monoamines (o el seu cofactor la tetrahidrobiopterina –BH4-), el GABA, la glicina i la serina, majoritàriament. Recentment també s’inclouen altres neurotransmissors com l’acetilcolina o l’ATP, i els trastorns astrocitaris o dels gliotransmissors. Les manifestacions clíniques es troben dins de l’espectre de les sinaptopaties, i es solen caracteritzar per discapacitat intel·lectual, epilèpsia, trastorns del moviment o símptomes neuropsiquiàtrics. Poden debutar en qualsevol edat de la vida, però característicament solen ser malalties neuropediàtriques que repercuteixen en el neurodesenvolupament, i que per tant, debuten en els primers anys de la vida. El treball que es presenta en aquesta tesi fa referència a: A) els defectes monogènics clàssics dels neurotransmissors, i B) els defectes de la fisologia sinàptica. A. En el primer treball es realitza una presentació del primer grup internacional dedicat a l’estudi de les malalties dels neurotransmissors, l’International Working Group on Neurotransmitter Related Disorders (iNTD), s’actualitza quina ha estat la seva activitat aquests darrers anys i el resultat principal en forma del primer registre internacional de pacients. En el següent treball, es presenta la segona guia de pràctica clínica d’un grup de defectes dels neurotransmissors: els defectes síntesi o reciclatge de la tetrahidrobiopterina (BH4). B. Els defectes de la fisiologia sinàptica implicarien totes aquelles malalties responsables d’alterar el procés de neurotransmissió i la biodisponibilitat/homeòstasi del neurotransmissor a l’espai sinàptic. En el següent treball es proposa una nova categoria de malaltia basada en el cicle biològic de la vesícula sinàptica, centrades en el terminal presinàptic de la neurona. Inclouria defectes en la formació de novo de la vesícula sinàptica al soma neuronal, el transport, maduració, exocitosi i reciclatge. Es proposa una categorització en quatre grups fenotípics: encefalopatia epilèptica, trastorns del moviment, discapacitat intel·lectual sindròmica i no-sindròmica, i trastorns neuromusculars. A propòsit de les malalties de la vesícula sinàptica, el següent treball presenta diferents pacients amb mutació en el gen DNAJC6, que codifica per l’auxilina 1 i participa en l’endocitosi de la vesícula sinàptica. El fenotip d’aquests pacients és en forma de discapacitat intel·lectual i distonia-parkinsonisme juvenil progressiva. S’estudia el líquid cefalorraquidi i fibroblasts, i s’analitzen l’auxilina 1, la ciclina-G associada a quinasa (GAK), i diferents proteïnes sinàptiques. Es conclou que hi ha una especial vulnerabiliat de l’homeòstasi dopaminèrgica, amb un augment probablement compensatori de la GAK. El següent treball descriu una pacient amb mutació en el gen DLP1, que també implica la neurotransmissió dopaminèrgica, tot codificant una proteïna que participa de l’endocitosi de la vesícula sinàptica i la fissió mitocondrial. El darrer treball amplia els defectes de la neurotransmissió centrant-se en el GABA. Es presenta una cohort de 85 pacients amb diferents malalties neuropediàtriques, i s’analitza la fracció de GABA lliure i monoamines en líquid cefalorraquidi. Es reporta una especial vulnerabilitat de la neurotransmissió GABAèrgica en tota la cohort en fins a un 44% dels casos (davant del 20% de defectes de les monoamines), i especialment en els errors congènits del metabolisme. Finalment, els annexos presenten la feina realitzada al llarg de tots aquests anys i amb la difusió d’aquests grups de malalties a través de les reunions amb famílies i amb professionals, i de la creació d’una pàgina web. D’aquesta manera, s’aconsegueix tancar el cercle que va des del pacient, a l’estudi de la seva malaltia de base i el defecte molecular, i el retorn al pacient a través del contacte estret amb les associacions de famílies i la comunitat científica., [eng] Neurotrasmission is the basic functional process devoted to neuronal communication, that takes place in the synaptic cleft. Classical neurotransmitter defects include disorders of the synthesis, metabolism or transport of monoamines (mainly dopamine and serotonin, but also adrenalin and noradrenalin), aminoacids (such as GABA and glutamate, but also serine and glycine, among others), or other molecules identified in the last decades as having a role in neurotransmission (i.e. ATP, lactate or acetylcholine). Main clinical symptoms manifest in the form of global developmental delay and intellectual disability, movement disorders, neuropsychiatric symptoms and epilepsy, all in the spectrum of synaptopathies. The current thesis encompasses: A) 2 publications related to the classical neurotransmitter defects; and B) 4 publications related to disorders of the synaptic physiology and neurotransmission (that influence the process of neurotransmission, its homeostasis and the biodisponibility of the neurotransmitter in the synaptic cleft, not directly related to synthesis, transport or metabolism defects), all of them focused in the presynaptic terminal. A. The former include: 1) the first publication of the International Working Group for Neurotransmitter Related Disorders (iNTD: http://intd-online.org/) and the initiation of the international registry for patients with neurotransmitter defects, as well as 2) the first clinical guidelines related to tetrahydrobiopterin synthesis and regeneration disorders. B. The latter include: 1) a proposal for a new category of presynaptic disorder, focused on the synaptic vesicle cycle; 2) a cohort of patients carrying DNAJC6 mutations, that encode the protein auxilin 1 (implicated in the endocytosis of the synaptic vesicle), and the secondary dopaminergic disruption in these patients, studied in cerebrospinal fluid (CSF) and fibroblasts; 3) a patient with DLP1 mutation, that encodes dynamin-like protein 1, implicated in the mitochondrial and peroxisomal fission, as well as the endocytosis of the synaptic vesicle; and finally, 4) a cohort of 85 patients with different neuropediatric disorders, in whom free GABA levels were studied in CSF, revealing a special vulnerability of GABA levels compared to monoamine levels, especially in the group of inborn errors of metabolism. Finally, the annexes of the thesis reveal the dissemination of the work among the scientific communities and the empowering of families.

Understanding the mapping between stimulus, behavior, and neural responses is vital for understanding sensory, motor, and general neural processing. We can examine this relationship through the complementary methods of encoding (predicting neural responses given the stimulus) and decoding (reconstructing the stimulus given the neural responses). The work presented in this thesis proposes, evaluates, and analyzes several nonlinear approaches for encoding and decoding that leverage recent advances in machine learning to achieve better accuracy. We first present and analyze a recurrent neural network encoding model to predict retinal ganglion cell responses to natural scenes, followed by a decoding approach that uses neural networks for approximate Bayesian decoding of natural images from these retinal cells. Finally, we present a probabilistic framework to distill behavioral videos into useful low-dimensional variables and to decode this behavior from neural activity.

An elusive phenomenon in network neuroscience is the extent of neuronal activity remodeling upon damage. Here, we investigate the action of gradual synaptic blockade on the effective connectivity in cortical networks in vitro. We use two neuronal cultures configurations—one formed by about 130 neuronal aggregates and another one formed by about 600 individual neurons—and monitor their spontaneous activity upon progressive weakening of excitatory connectivity. We report that the effective connectivity in all cultures exhibits a first phase of transient strengthening followed by a second phase of steady deterioration. We quantify these phases by measuring GEFF, the global efficiency in processing network information. We term hyperefficiency the sudden strengthening of GEFF upon network deterioration, which increases by 20–50% depending on culture type. Relying on numerical simulations we reveal the role of synaptic scaling, an activity–dependent mechanism for synaptic plasticity, in counteracting the perturbative action, neatly reproducing the observed hyperefficiency. Our results demonstrate the importance of synaptic scaling as resilience mechanism., Author Summary Neuronal circuits exhibit homeostatic plasticity mechanisms to cope with perturbations or damage. A central mechanism is ‘synaptic scaling,’ a self-organized response in which the strength of neurons’ excitatory synapses is adjusted to compensate for activity variations. Here we present experiments in which the excitatory connectivity of in vitro cortical networks is progressively weakened through chemical action. The spontaneous activity and effective connectivity of the whole network is monitored as degradation progresses, and the capacity of the network for broad information communication is quantified through the global efficiency. We observed that the network responded to the perturbation by strengthening the effective connectivity, reaching a hyperefficient state for moderate perturbations. The study proves the importance of ‘synaptic scaling’ as a driver for functional reorganization and network-wide resilience.

Neurofilament (NFL) proteins have recently been found to play unique roles in synapses. NFL is known to interact with the GluN1 subunit of N-methyl-d-aspartic acid (NMDAR) and be reduced in schizophrenia though functional consequences are unknown. Here we investigated whether the interaction of NFL with GluN1 modulates synaptic transmission and schizophrenia-associated behaviors. The interaction of NFL with GluN1 was assessed by means of molecular, pharmacological, electrophysiological, magnetic resonance spectroscopy (MRS), and schizophrenia-associated behavior analyses. NFL deficits cause an NMDAR hypofunction phenotype including abnormal hippocampal function, as seen in schizophrenia. NFL−/− deletion in mice reduces dendritic spines and GluN1 protein levels, elevates ubiquitin-dependent turnover of GluN1 and hippocampal glutamate measured by MRS, and depresses hippocampal long-term potentiation. NMDAR-related behaviors are also impaired, including pup retrieval, spatial and social memory, prepulse inhibition, night-time activity, and response to NMDAR antagonist, whereas motor deficits are minimal. Importantly, partially lowering NFL in NFL+/− mice to levels seen regionally in schizophrenia, induced similar but milder NMDAR-related synaptic and behavioral deficits. Our findings support an emerging view that central nervous system neurofilament subunits including NFL in the present report, serve distinctive, critical roles in synapses relevant to neuropsychiatric diseases.

SummaryAMPARs control fast synaptic communication between neurons and their function relies on auxiliary subunits, which importantly modulate channel properties. Although it has been suggested that AMPARs can bind to TARPs with variable stoichiometry, little is known about the effect that this stoichiometry exerts on certain AMPAR properties. Here we have found that AMPARs show a clear stoichiometry dependent modulation although AMPARs still need to be fully saturated with TARPs to show some typical TARP-induced characteristics (i.e. an increase in channel conductance). We also have uncovered important differences in the stoichiometric modulation between calcium-permeable and calcium-impermeable AMPARs. Moreover, in heteromeric AMPARs, TARP positioning in the complex is important to exert certain TARP-dependent features. Finally, by comparing data from recombinant receptors with endogenous AMPAR currents from cerebellar granule cells, we have determined a likely functional stoichiometry of 2 TARPs associated with GluA2 subunits in the somatic AMPARs found in this cell type.

The hub-and-spoke model of semantic cognition seeks to reconcile embodied views of a fully distributed semantic network with patient evidence, primarily from semantic dementia, who demonstrate modality-independent conceptual deficits associated with atrophy centred on the ventrolateral anterior temporal lobe. The proponents of this model have recently suggested that the temporal cortex is a graded representational space where concepts become less linked to a specific modality as they are processed farther away from primary and secondary sensory cortices and towards the ventral anterior temporal lobe. To explore whether there is evidence that the connectivity patterns of the temporal lobe converge in its ventral anterior end the current study uses three dimensional Laplacian eigenmapping, a technique that allows visualisation of similarity in a low dimensional space. In this space similarity is encoded in terms of distances between data points. We found that the ventral and anterior temporal lobe is in a unique position of being at the centre of mass of the data pointswithin the connective similarity space. This can be interpreted as the area where the connectivity profiles of all other temporal cortex voxels converge. This study is the first to explicitly investigate the pattern of connectivity and thus provides the missing link in the evidence that the ventral anterior temporal lobe can be considered a multi-modal graded hub., peer-reviewed

Atypical responses to sound are common in individuals with autism spectrum disorder (ASD), and growing evidence suggests an underlying auditory brainstem pathology. This review of the literature provides a comprehensive account of the structural and functional evidence for auditory brainstem abnormalities in ASD. The studies reviewed were published between 1975 and 2016 and were sourced from multiple online databases. Indices of both the quantity and quality of the studies reviewed are considered. Findings show converging evidence for auditory brainstem pathology in ASD, although the specific functions and anatomical structures involved remain equivocal. Two main trends emerge from the literature: (1) abnormalities occur mainly at higher levels of the auditory brainstem, according to structural imaging and electrophysiology studies; and (2) brainstem abnormalities appear to be more common in younger than older children with ASD. These findings suggest delayed maturation of neural transmission pathways between lower and higher levels of the brainstem and are consistent with the auditory disorders commonly observed in ASD, including atypical sound sensitivity, poor sound localization, and difficulty listening in background noise. Limitations of existing studies are discussed, and recommendations for future research are offered.

Background: GRIN-related disorders (GRD), the so-called grinpathies, is a group of rare encephalopathies caused by mutations affecting GRIN genes (mostly GRIN1, GRIN2A and GRIN2B genes), which encode for the GluN subunit of the N-methyl D-aspartate (NMDA) type ionotropic glutamate receptors. A growing number of functional studies indicate that GRIN-encoded GluN1 subunit disturbances can be dichotomically classified into gain- and loss-of-function, although intermediate complex scenarios are often present. Methods: In this study, we aimed to delineate the structural and functional alterations of GRIN1 disease-associated variants, and their correlations with clinical symptoms in a Spanish cohort of 15 paediatric encephalopathy patients harbouring these variants. Results: Patients harbouring GRIN1 disease-associated variants have been clinically deeply-phenotyped. Further, using computational and in vitro approaches, we identified different critical checkpoints affecting GluN1 biogenesis (protein stability, subunit assembly and surface trafficking) and/or NMDAR biophysical properties, and their association with GRD clinical symptoms. Conclusions: Our findings show a strong correlation between GRIN1 variants-associated structural and functional outcomes. This structural-functional stratification provides relevant insights of genotype-phenotype association, contributing to future precision medicine of GRIN1-related encephalopathies.

Demyelination of central nervous system axons, associated with traumatic injury and demyelinating diseases such as multiple sclerosis, causes impaired neural transmission and ultimately axon degeneration. Consequently, extensive research has focused on signaling systems that promote myelinating activity of oligodendrocytes or promote production of new oligodendrocytes from oligodendrocyte progenitor cells. Many receptor systems, notably including growth factor receptors and G protein–coupled receptors, control myelination. A number of recent clinical trials target these receptor signaling pathways.

RESUMO Introdução Poucos estudos realizaram, concomitantemente, o potencial evocado auditivo de tronco encefálico (PEATE) e o P300 na Síndrome de Down (SD), em indivíduos audiologicamente normais, para a avaliação da via auditiva central, principalmente pela dificuldade de realizar estes procedimentos nesta população. Estudos anteriores sugeriram que indivíduos com SD podem apresentar padrões de respostas diferentes das encontradas em indivíduos com desenvolvimento típico, sendo que a identificação destes seria fundamental para o estabelecimento de um diagnóstico audiológico preciso. Objetivo Caracterizar o PEATE e o P300 em indivíduos com SD audiologicamente normais. Método Foram analisados o PEATE e o P300 de 17 indivíduos com SD e 21 com desenvolvimento típico de sete a 15 anos. A análise foi quantitativa e qualitativa, utilizando medidas descritivas e os testes de hipótese. Resultados Os valores de latência foram menores no PEATE para o grupo SD, com diferença estatisticamente significante para a onda V, interpicos III-V e I-V; não foram encontradas diferenças significantes nos valores de latência do P300. Observou-se maior número de indivíduos com valores precoces para as latências do PEATE e com latências atrasadas para o P300 no grupo SD; ambas as comparações mostraram diferenças significantes. Conclusão Crianças e adolescentes com SD podem apresentar respostas precoces para os componentes do PEATE, sugerindo que a via auditiva destes necessita de menor tempo para a transmissão neural do estímulo acústico até o tronco encefálico. Quanto ao P300, indivíduos com SD podem apresentar latências aumentadas, sugerindo comprometimento na via auditiva central quanto ao processamento cortical da informação auditiva. ABSTRACT Introduction Few studies have performed Brainstem (BAEP) and P300 Auditory Evoked Potentials simultaneously to assess central auditory pathways in normal hearing individuals with Down syndrome (DS), mainly because of the difficulty in applying these procedures to this population. Previous studies have suggested that individuals with DS might present different patterns of response compared with those of individuals with typical development; nevertheless, the identification of these potentials would be crucial for the establishment of an accurate audiological diagnosis. Purpose To characterize BAEP and P300 in normal-hearing individuals with DS. Methods BAEP and P300 were analyzed in 17 individuals with DS and in 21 individuals with typical development aged 7 to 15 years. The results were quantitatively and qualitatively analyzed using descriptive measures and hypothesis tests. Results In the quantitative analysis, latency values were lower in the BAEP for the DS group, with statistically significant difference for wave V and interpeaks III-V and I-V; there were no significant differences in the P300 latency values. In the qualitative analysis, there were a larger number of individuals with early values for BAEP latencies and late latencies for P300 in the DS group; both comparisons showed statistically significant differences. Conclusion Children and adolescents with DS can present early responses to the components of BAEP, suggesting that their auditory pathway requires less time for the neural transmission of acoustic stimuli to the brainstem. Concerning P300, individuals with DS may present increased latencies, suggesting impairment in the central auditory pathway for the cortical processing of auditory information.

The erector spinae plane (ESP) block has been widely adopted despite a lack of randomized control trials supporting its efficacy. The mechanism of action remains elusive despite several cadaver studies. Using human volunteers is important as the spread of local anesthetic is influenced by the

Background This study assessed the effect of blockading neural transmission in the ganglionated plexi by injecting lidocaine into fat pads in the vagal nerve stimulation canine model and patients with persistent atrial fibrillation ( AF ). Methods and Results An efficacy test of lidocaine injection was performed in 7 canines. During vagal nerve stimulation, AF was sustained for >5 minutes. The lidocaine was injected into ganglionated plexi during sinus rhythm and reinduction of AF was attempted. Six patients with persistent AF were studied at open heart surgery. Lidocaine was injected into ganglionated plexi. Atrial electrograms were recorded from 96 epicardial electrodes covering Bachmann's bundle and atrial appendages. In the canine vagal nerve stimulation AF model, AF was not inducible in 4 of 7 after lidocaine injection. In patients with persistent AF , during baseline AF , there was a left atrium ( LA )‐to‐right atrium ( RA ) frequency gradient ( LA , mean cycle length [ CL ] 175±17 ms; RA , mean CL 192±17 ms; P AF persisted in all patients, and the LA ‐to‐ RA frequency gradient disappeared ( LA , mean CL 186±13 ms; RA , mean CL 199±23 ms; P =0.08). Comparison of mean CL s before and after lidocaine demonstrated prolongation of LA CL s ( P RA CL s. Conclusions In the canine vagal nerve stimulation AF model, lidocaine injection decreased inducibility of AF . In patients with persistent AF , atrial electrograms from the LA had shorter CL s than RA , indicating an LA ‐to‐ RA frequency gradient. Lidocaine injection significantly prolonged only LA CL s, explaining disappearance of the LA ‐to‐ RA frequency gradient. The mechanism of localized atrial electrogram CL prolongation in patients with persistent AF is uncertain.

Bimanual motor actions, such as threading a needle, require coordination of the movements of each hand according to the state of the other hand. By connecting homologous cortical regions between the two cerebral hemispheres, the corpus callosum is thought to play a key role in such bimanual coordination. However, direct experimental evidence of the contribution of the corpus callosum to natural behaviors requiring bimanual coordination, such as feeding, is lacking. We investigated the hypothesis that the corpus callosum mediates bimanual movements during food-handling behavior. We first traced the forelimb-related components of the motor corpus callosum in Long-Evans rats, and found that the callosal fiber bundle from the forelimb motor areas passes through the anterior part of the corpus callosum. We then confirmed by electrophysiological recordings that blocking the axonal conduction of fibers in the anterior corpus callosum reduced neural transmission between cortical forelimb areas. The causal role of corpus callosum in bimanual coordination was then tested by analyzing forelimb kinematics during object manipulation, before and after blocking axonal conduction in the anterior corpus callosum. We found the frequency of occurrence of symmetric bimanual movements was reduced by inhibition of anterior corpus callosum. In contrast, asymmetric bimanual movement was increased. Our findings suggest that the anterior corpus callosum coordinates the direction of bimanual movement.

Visual Abstract, Hierarchical predictive coding is an influential model of cortical organization, in which sequential hierarchical levels are connected by backward connections carrying predictions, as well as forward connections carrying prediction errors. To date, however, predictive coding models have largely neglected to take into account that neural transmission itself takes time. For a time-varying stimulus, such as a moving object, this means that backward predictions become misaligned with new sensory input. We present an extended model implementing both forward and backward extrapolation mechanisms that realigns backward predictions to minimize prediction error. This realignment has the consequence that neural representations across all hierarchical levels become aligned in real time. Using visual motion as an example, we show that the model is neurally plausible, that it is consistent with evidence of extrapolation mechanisms throughout the visual hierarchy, that it predicts several known motion–position illusions in human observers, and that it provides a solution to the temporal binding problem.

[spa] Los gabapentinoides son una familia de fármacos que se unen con gran afinidad a la subunidad α2δ-1 de los canales de calcio voltaje-dependientes (VGCCs). Fármacos de esta familia como la pregabalina o la gabapentina se utilizan como tratamientos de primera línea para aliviar el dolor neuropático en enfermedades como la fibromialgia, la neuropatía diabética o la neuralgia del trigémino. Sin embargo, su uso extensivo contrasta con el limitado conocimiento sobre las implicaciones funcionales que produce la interacción de los gabapentinoides con la subunidad α2δ-1 y cuáles son sus efectos sobre la neurotransmisión. Los resultados generados a lo largo de esta tesis ayudan a obtener una imagen más nítida sobre la capacidad de la pregabalina para modificar la neurotransmisión de forma aguda. Estudiando la población homogénea de sinapsis presentes en los cultivos autápticos de neuronas colinérgicas del ganglio cervical superior de rata (SCMs), demostramos que la interacción de la pregabalina y del ectodominio de la neurexina-1α con la subunidad α2δ-1 inhibe la liberación sincrónica de vesículas sinápticas controlada por los canales de calcio dependientes de voltaje de tipo N, de forma aguda. Visualizando de manera simultánea la entrada de calcio presináptico mientras registramos las respuestas postsinápticas, comprobamos que el efecto de la pregabalina no está relacionado con una reducción significativa en la entrada de calcio presináptico. Por el contrario, el efecto reside en una alteración de la organización física establecida entre los canales de calcio y las vesículas sinápticas de la zona activa, reduciéndose de manera notable el tamaño efectivo del depósito de vesículas de liberación rápida. Asimismo, comprobamos que la sobreexpresión de la subunidad α2δ-1 potencia los efectos observados con la pregabalina y la neurexina-1α en la neurotransmisión; efectos que son mutuamente excluyentes. En esta tesis desvelamos la implicación de la región extracelular de la neurexina-1α en la regulación de la liberación de neurotransmisores. Debido a su privilegiada localización extracelular en las zonas activas, las subunidades α2δ sinápticas emergen como una diana sináptica común desde donde fármacos como los gabapentinoides o moléculas endógenas como el ectodominio de la neurexina-1 pueden controlar de forma aguda el acoplamiento entre los canales de calcio voltaje-dependientes con la liberación de las vesículas sinápticas del RRP. La variabilidad en la composición molecular de las sinapsis, como por ejemplo los niveles de α2δ presentes en los pacientes que padecen dolor neuropático, así como un posible incremento de los niveles de la región extracelular de la neurexina-1α durante las condiciones inflamatorias relacionadas con el dolor neuropático, podrían ser factores claves para explicar la efectividad del tratamiento con los gabapentinoides., [eng] Gabapentinoids are drugs that bind with high affinity voltage-gated calcium channel alpha2delta subunits. For example, α2δ-1 binds with high-affinity gabapentinoid drugs such as gabapentin (2-(1-(aminomethyl)-cyclohexyl) acetic acid) or pregabalin (3-(aminomethyl)-5-methyl-hexanoic acid), which are widely used for treating neuropathic pain. The present study sheds new light on how the interaction of gabapentinoids with alpha2delta subunits affects neurotransmission. Here we show that α2δ-1 operates as a molecular platform binding exogenous and endogenous ligands to acutely regulate the size of the readily releasable pool (RRP). The RRP of synaptic vesicles is a key determinant of phasic neurotransmission. Although the size of the RRP is tightly regulated by intracellular factors, there is little evidence for its modification by extracellular signals. By studying the homogeneous population of synapses present in autaptic microcultures, we show that pregabalin decreases the effective RRP size. Simultaneous imaging of presynaptic calcium influx and recording of postsynaptic responses shows that the effect is not related to a reduction of calcium entry. The main cause is the impairment of the functional coupling among N-type calcium channels and the RRP, resembling an increase of intracellular mobile calcium buffers such as BAPTA and/or EGTA. The ectodomain of neurexin-1α shows a similar action to pregabalin, acting as an endogenous ligand of α2δ-1 that reduces the RRP size without affecting presynaptic calcium influx. The regulatory actions described for pregabalin and the ectodomain of neurexin-1α are mutually exclusive. The overexpression of α2δ-1 enhances the effect of pregabalin and the ectodomain of neurexin-1α on neurotransmission by decreasing their effective concentration. In contrast, knockdown of α2δ-1 causes a profound inhibition of synaptic transmission. These observations prompt to consider α2δ-1 as an outside-in signaling platform that binds exogenous and endogenous cues for regulating the coupling of voltage-gated calcium channels to synaptic vesicles.

Summary: SNARE-mediated synaptic vesicle (SV) fusion is controlled by multiple regulatory proteins that determine neurotransmitter release efficiency. Complexins are essential SNARE regulators whose mode of action is unclear, as available evidence indicates positive SV fusion facilitation and negative “fusion clamp”-like activities, with the latter occurring only in certain contexts. Because these contradictory findings likely originate in part from different experimental perturbation strategies, we attempted to resolve them by examining a conditional complexin-knockout mouse line as the most stringent genetic perturbation model available. We found that acute complexin loss after synaptogenesis in autaptic and mass-cultured hippocampal neurons reduces SV fusion probability and thus abates the rates of spontaneous, synchronous, asynchronous, and delayed transmitter release but does not affect SV priming or cause “unclamping” of spontaneous SV fusion. Thus, complexins act as facilitators of SV fusion but are dispensable for “fusion clamping” in mammalian forebrain neurons. : Complexins are thought to either promote synaptic vesicle fusion or act as “fusion clamps.” López-Murcia et al. show that acute genetic complexin deletion reduces the rates of all forms of transmitter release in forebrain neurons without affecting vesicle priming. Thus, complexins are facilitators of vesicle fusion and dispensable for “fusion clamping.” Keywords: complexin, synaptic vesicle, fusion, hippocampal neurons, synaptic transmission

When animals encounter conflict they initiate and escalate aggression to establish and maintain a social hierarchy. The neural mechanisms by which animals resolve fighting behaviors to determine such social hierarchies remain unknown. We identified two subregions of the dorsal habenula (dHb) in zebrafish that antagonistically regulate the outcome of conflict. The losing experience reduced neural transmission in the lateral subregion of dHb (dHbL)-dorsal/intermediate interpeduncular nucleus (d/iIPN) circuit. Silencing of the dHbL or medial subregion of dHb (dHbM) caused a stronger predisposition to lose or win a fight, respectively. These results demonstrate that the dHbL and dHbM comprise a dual control system for conflict resolution of social aggression.

Nitric oxide (NO) is a gas that plays various roles in physiological signal transduction, for example, in vasodilation, neural transmission, and biodefence. Recently, other gaseous signal mediators such as carbon monoxide (CO) and hydrogen sulfide (H2S) have also been found to have important biological activities. Since experimental studies with gaseous mediators are difficult, chemicals that enable controlled release of these gases are indispensable. We have developed a range of photocontrollable releasers that generate NO, H2S, and related species with fine spatiotemporal control, and we have also employed these caged compounds in various applications. This paper briefly reviews our work on photocontrollable NO, H2S, and HNO releasers, and presents some typical applications illustrating the suitability of our compounds for controlled release of these biologically active species in cellular and tissue systems. These compounds also appear to have potential for future therapeutic applications.

To elucidate the role of autonomic nervous system in functional dyspepsia patients, we examined 24-h heart rate variability: the basal levels, responses after lunch, cold pressor and mental arithmetic tests, and the efficacy of an autonomic drug (tofisopam). The high-frequency component (HF: 0.15–0.40 Hz) and the ratio of HF to the low-frequency component (LF: 0.04–0.15 Hz; LF/HF ratio) were used as indicators of parasympathetic and sympathetic autonomic nervous system function. The HF component in the 24-h, daytime, and nighttime was low in 86.7%, 97.8%, and 66.7% of patients (n = 45) and the LF/HF ratio was high in 51.1%, 73.3%, and 26.6% of patients. Gastrointestinal symptom tended to be severe in patients with autonomic nervous system disorder (p = 0.085). The abnormal response in HF component after lunch occurred in 38.2% (13/34) of patients who revealed a greater tendency towards in indigestion score (p = 0.061). Delays in recovery to the basal autonomic nervous system level after stimulus of the cold pressor and the mental arithmetic tests occurred in parts of patients. Tofisopam partially improved autonomic nervous system dysfunction and abdominal pain/indigestion. Imbalanced autonomic nervous system function and vulnerability for recovery from external stimuli were observed in functional dyspepsia patients, which was associated with dyspeptic symptoms.

A previous exposition of apraxia in Practical Neurology 1 offered an account of underlying impairment and accompanying clinical assessment based on a distinction between ideational, ideomotor and limb-kinetic apraxia. This conceptualisation stems from 19th-century models of higher cortical motor, language and visual function, revived by Geschwind2 3 in the 1960s. Liepmann in 19004 had posited a hierarchical model of action control over three discrete levels. At the top, movement formulae (‘visual engrams’ of the action) provided overall targets, which activate innervatory patterns to stimulate the appropriate muscles, coordinated contraction of muscles then led to execution of the action. (1) Ideational apraxia arose when movement formulae were either impaired or disconnected from the innervatory patterns. (2) Ideomotor apraxia resulted from disruption to innervatory patterns. (3) Limb-kinetic apraxia , assumed to be a disruption to the smooth neural transmission of the motor commands, was, even for Liepmann, not a full apraxia. It existed between apraxia and paresis only within a broader view of dysfunction. Liepmann’s model proved valuable in studying apraxia. However, despite surviving in several neurology textbooks, the ideational–ideomotor dichotomy has now been replaced as a way of understanding and classifying apraxias,5–8 similar to the disbandment of Broca’s versus Wernicke’s aphasia, or the dichotomy of associative versus apperceptive agnosia9 (although these distinctions, too, still persist in some areas of clinical practice). A radical rethink was needed, owing to issues with the underlying theoretical model of apraxia and difficulties in distinguishing between ideational and ideomotor clinically. Goldenberg7 made the plea to ‘relegate the dichotomy of ideational …

We recently provided evidence that an intrinsic reward-related signal—triggered by successful learning in absence of any external feedback—modulated the entrance of new information into long-term memory via the activation of the dopaminergic midbrain, hippocampus, and ventral striatum (the SN/VTA-Hippocampal loop; Ripollés et al., 2016). Here, we used a double-blind, within-subject randomized pharmacological intervention to test whether this learning process is indeed dopamine-dependent. A group of healthy individuals completed three behavioral sessions of a language-learning task after the intake of different pharmacological treatments: a dopaminergic precursor, a dopamine receptor antagonist or a placebo. Results show that the pharmacological intervention modulated behavioral measures of both learning and pleasantness, inducing memory benefits after 24 hr only for those participants with a high sensitivity to reward. These results provide causal evidence for a dopamine-dependent mechanism instrumental in intrinsically regulated learning and further suggest that subject-specific reward sensitivity drastically alters learning success.

The temporal lobe has been associated with various cognitive functions which include memory, auditory cognition and semantics. However, at a higher level of conceptualisation, all of the functions associated with the temporal lobe can be considered as lying along one major axis; from modality-specific to modality-general processing. This paper used a spectral reordering technique on resting-state and task-based functional data to extract the major organisational axis of the temporal lobe in a bottom-up, data-driven fashion. Independent parcellations were performed on resting-state scans from 71 participants and active semantic task scans from 23 participants acquired using dual echo gradient echo planar imaging in order to preserve signal in inferior temporal cortex. The resulting organisational axis was consistent (over dataset and hemisphere) and progressed from superior temporal gyrus and posterior inferior temporal cortex to ventrolateral anterior temporal cortex. A hard parcellation separated a posterior (superior temporal and posterior fusiform and inferior temporal gyri) and an anterior cluster (ventrolateral anterior temporal lobe). The functional connectivity of the hard clusters supported the hypothesis that the connectivity gradient separated modality-specific and modality-general regions. This hypothesis was then directly tested by performing a VOI analysis upon an independent semantic task-based data set including auditory and visually presented stimuli. This confirmed that the ventrolateral anterior aspects of the temporal lobe are associated with modality-general processes whilst posterior and superior aspects are specific to certain modalities, with the posterior inferior subregions involved in visual processes and superior regions involved in audition., This work was supported by a doctoral prize from the Engineering and Physical Sciences Research Council (RLJ), a studentship from the BBSRC (BB/J014478/1 to CJB) and a programme grant from the Medical Research Council (MR/J004146/1 to MALR). The funding sources had no role in study design, data collection, analysis and interpretation, report writing or the submission decision., peer-reviewed

Fast excitatory neurotransmission is critical for learning and memory, and its dysregulation is linked to numerous neurological diseases. These include developmental diseases such as fragile X syndrome, psychiatric disorders like schizophrenia, and chronic neurodegenerative disorders such as Parkinson’s and Alzheimer’s diseases. Throughout the central nervous system, AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid)-subtype ionotropic glutamate receptors (AMPARs) mediate the fastest excitatory neurotransmission. In response to the neurotransmitter glutamate, AMPARs open their ion channels and allow cation flux through the post-synaptic membrane. This initiates rapid depolarization and signaling in the post-synaptic neuron. Nearly all AMPARs exist as complexes with auxiliary subunits, which are regulatory proteins that modulate receptor assembly, trafficking, pharmacology and function. These auxiliary subunits determine brain region-specific AMPAR signaling, and aberrancies in complex formation or function lead to neuropathologies. Despite their importance for CNS signaling and implication in neurologic disorders, the structural bases underlying the function of AMPARs and AMPAR complexes remain ambiguous, representing a critical barrier to our understanding of excitatory neurotransmission. As a consequence, structure-based design of neuro-therapeutics is largely undeveloped: there is only a single FDA-approved drug targeting AMPARs. To address these problems, I wanted to dedicate my thesis work to study AMPAR synaptic complexes across an array of functional states and provide a new foundation for our structural understanding of AMPAR signaling. First, I designed a covalent-fusion construct approach to guarantee assembly and expression of AMPAR synaptic complexes in heterologous cells (HEK293). Then, I developed purification protocols allowing me to obtain chemically homogenous and pure complex protein. Since synaptic signaling is highly dynamic, complexes of AMPARs with auxiliary subunits are conformationally heterogeneous and are not amenable to X-ray crystallography. Cryo-electron microscopy (cryo-EM) enabled me to approach these complexes structurally, where I could collect data and parse out heterogeneity through image classification. With cryo-EM, I solved the structure of an AMPAR bound to the auxiliary subunit stargazin, which promotes AMPAR activation. This work provided the first structural information on how AMPARs form complexes with regulatory subunits. In a following study, I solved the structure of an AMPAR in complex with a functionally distinct auxiliary subunit, GSG1L. In contrast to stargazin, GSG1L promotes inactivation and desensitization of AMPARs, thus having a neuroprotective effect. To further characterize the function of these auxiliary subunits, I designed chimeras between stargazin and GSG1L and examined their function electrophysiologically. This experiment revealed that AMPAR auxiliary subunits have a modular design, where variable extracellular domain regions, supported by a conserved transmembrane α-helical bundle, distinctly regulate function of the core AMPAR. This study provided the first evidence of how brain region-specific expression patterns of similarly-structured auxiliary subunits may contribute to unique AMPAR functions. More recently, I’ve taken advantage of the modulatory effects of stargazin on AMPARs and I applied cryo-EM to an AMPAR-stargazin complex. This study determined how AMPARs are activated by the neurotransmitter glutamate, and revealed a novel mechanism by which glutamate binding induces opening of AMPAR ion channels. Our data show that two-fold symmetric kinking of ion channel helices allows cation flux into neurons, which triggers neurotransmission. Importantly, this study also provides insights into how mRNA editing and patient-derived disease mutations in the transmembrane (i.e., resulting in aberrantly firing of receptors during epilepsy) reshape AMPAR function and excitatory neurotransmission. Collectively, the findings from my thesis work provide a new paradigm for the molecular-level understanding of glutamatergic neurotransmission throughout the CNS. These studies lay the groundwork for new directions in precision-medicine design of therapeutics targeting brain region-specific AMPAR synaptic complexes in neurological diseases.

Cocaine addiction is a chronic, relapsing disease characterized by the heavy use of, aberrant motivation for, and an inability to maintain abstinence from cocaine. Considerable effort has been directed towards understanding the factors underlying the risk for cocaine addiction; however, the mechanisms that predispose individuals to develop the disease remain unclear. The mesolimbic dopamine system has been particularly implicated in the reinforcing effects of cocaine, which enhances extracellular dopamine in this system primarily by inhibiting dopamine uptake. Recent evidence suggests that inherent variability in dopamine neurotransmission may influence the risk for developing cocaine addiction. To determine the relative contributions of dopamine release and uptake to the vulnerability to use cocaine, we first employed a novel application of fast scan cyclic voltammetry in anesthetized male rats to construct a neurochemical profile of DA signaling in the medial dorsal striatum (mDS) and ventral striatum of individual animals under baseline, drug-naïve conditions--prior to any behavioral testing. Following recovery, rats were either allowed to self-administer cocaine or were induced to develop cocaine conditioned place preference (CPP). Results suggest that there is no significant relationship between dopamine release or uptake and the acquisition of either CPP or operant self-administration, nor did we identify a significant relationship between dopamine signaling and the consumption of cocaine. We did, however, identify a strong, linear relationship between dopamine uptake in the mDS and the motivation for cocaine under progressive ratio and threshold schedules of reinforcement as well as cocaine-primed reinstatement--implicating DAT function in the risk for aberrant motivation associated with cocaine addiction. Moreover, results using ex vivo voltammetry suggest that inherent variability in dopamine uptake mediates the neurochemical sensitivity to cocaine, suggesting that faster rates of uptake may enhance the interoceptive properties of cocaine. Finally, preliminary results using viral manipulations to reduce DA uptake further suggest that DA uptake governs motivation for cocaine. Together, these data suggest that inherent variability in the mesolimbic dopamine system may underlie behavioral components associated with cocaine abuse.

Itch, or pruritus, is a hallmark feature of atopic dermatitis (AD). The impact of AD-related pruritus can range from mildly distressing or distracting to completely disabling. Traditionally, management of itch in AD patients has focused on restoring the altered skin barrier with topical emollients and/or reducing inflammation. A growing emphasis has been placed on directly targeting the neural transmission pathways that mediate itch signaling. Off-label use of neuromodulatory agents has helped reduce this aggravating symptom in atopic patients. This article reviews the current literature on the use of neuromodulatory agents and nonpharmacologic alternative therapies used to treat AD-related pruritus.

Sustained and elevated activity during the working memory delay period has long been considered the primary neural correlate for maintaining information over short time intervals. This idea has recently been reinterpreted in light of findings generated from multiple neural recording modalities and levels of analysis. To further investigate the sustained or transient nature of activity, the temporal-spectral evolution (TSE) of delay period activity was examined in humans with high density EEG during performance of a Sternberg working memory paradigm with a relatively long six second delay and with novel scenes as stimuli. Sensor level analyses revealed transient rather than sustained activity during delay periods. Specifically, high amplitude activity encompassing the theta range was found early, during the first three seconds of the delay and correlated positively with subsequent ability to distinguish new from old probe scenes. Later, toward the end of the delay, lower amplitude activity encompassing the alpha/beta range was found that negatively correlated with subsequent ability to distinguish probes. Source level signal estimation implicated a right parietal region of transient early delay activity that correlated positively with working memory ability. Importantly, varying the trial temporal window duration and changing the baseline period for computation of TSE activity were found to influence the strength of the correlations obtained. This pattern of results adds to recent evidence that transient rather than sustained delay period activity supports visual working memory performance. The findings are discussed in relation to synchronous and desynchronous intra- and inter-regional neural transmission, and choosing an optimal baseline for expressing temporal-spectral delay activity change.

The Alzheimer’s disease is a disorder characterized by the presence of senile plaques and neurofibrillary tangles caused by the aberrant accumulation of β-amyloid peptide and hyperphosphorylated Tau, respectively. Nowadays, AD is the main cause of dementia, being aging its main risk factor. Given that progressive alterations have been detected in neuropeptide levels in patients and animal models of Alzheimer's disease, it has been suggested that this pathway may be involved in the neurophysiology of the disease. In this doctoral thesis, we study the cortical alterations of the peptidergic secretion pathway in Alzheimer's disease. During its elaboration, the localization of dense granule proteins in the normal brain has been characterized and aberrant accumulations of these are found in the pathological structures typical of the disease, such as granulovacuolar degeneration bodies or dystrophic neurites. The study of the acute effect of β-amyloid peptide showed a reduction of the regulated peptidergic release in neurons and astrocytes in vitro as well as in acute brain slices in response to the treatment, suggesting that the secretion pathway can suppose an early target of the pathology. Finally, the content analysis of characteristic proteins of the pathway showed a reduction of their levels in the cerebrospinal fluid of transgenic animals and patients with mild cognitive impairment, which may suggest that the proteins of the route can be candidates as progression biomarkers to monitoring of the progression of Alzheimer's disease., La enfermedad de Alzheimer es un trastorno neurodegenerativo caracterizado por la presencia de placas seniles y ovillos neurofibrilares causados por la acumulación patológica del péptido β-amiloide y la hiperfosforilación de Tau, respectivamente. En la actualidad, la enfermedad de Alzheimer constituye la principal causa de demencia y su principal factor de riesgo es el envejecimiento. Dado que se han detectado alteraciones progresivas en los niveles de neuropéptidos en pacientes y modelos animales de la enfermedad de Alzheimer, se ha sugerido que esta vía pueda estar implicada en la neurofisiología de la enfermedad. En esta tesis doctoral se realiza un estudio de las alteraciones corticales de la vía de secreción peptidérgica en la enfermedad de Alzheimer. Durante su elaboración se ha caracterizado la localización de las proteínas de los gránulos densos en el cerebro normal y patológico, encontrándose acúmulos aberrantes de las mismas en las estructuras patológicas típicas de la enfermedad, como son los cuerpos de degeneración granulovacuolar o las neuritas distróficas. El estudio del efecto agudo del péptido β-amiloide permitió hallar una reducción de la liberación regulada tanto en neuronas y astrocitos in vitro como en rodajas de cerebro agudas en respuesta al tratamiento, sugiriendo que la vía de secreción puede suponer una diana temprana de la patología. Finalmente, el estudio de los niveles de proteínas características de la vía ha mostrado una reducción de sus niveles en el líquido cefalorraquídeo de animales transgénicos y pacientes de la enfermedad con deterioro cognitivo leve, lo que parece indicar que las proteínas de la vía pueden ser candidatas como biomarcadores que permitan la monitorización del avance de la enfermedad de Alzheimer.

Parkinson’s disease (PD) is increasingly recognized as a heterogeneous disorder combining equally diverse motor and non-motor symptoms, with a complex interplay and different individual presentations, especially in the advanced stages of the disease. Current classifications and related stage-adapted therapeutic recommendations still lack of precision, as traditional concepts of advanced PD (advPD) are mainly based on milestones of motor disabilities. In this short review, we present the concepts delineated by Kruger and colleagues published in the ‘Journal of Neural Transmission’ on current classifications for advPD and novel directions for future clinical trials, a precision medicine approach by empowerment of patients and their involvement in therapeutic decisions.