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Purpose The usage of open-source hardware (OSH) designs has been put forward as a means to mitigate the shortage of core medical equipment, such as ventilators and of personal protection equipment (PPE) in medical facilities worldwide, resulting from the ever increasing number of individuals affect by COVID-19. This is due to the model allowing for the lowering of costs and widespread distribution of manufacturing. On the other hand, low adherence to its best practices and insufficient development may jeopardize OSH as a viable aid against the pandemic. In this work, we sought to clarify to what extent publicly available designs of ventilator and PPE are developed and abide by OSH standards as measure of the true openness of the solutions. Methods We searched the Internet and the literature to compile a comprehensive list of ventilators and PPE, while assessing available documentation in order to objectively evaluate key development landmarks (e.g., testing and governmental clearance) and indicators of adherence by OSH standards, as described by the Open Source Hardware Association. Results Only a few peer-reviewed articles have been found, while a good number of Internet entries of open ventilator and PPE designs were found. Available documentation varied a lot in quantity and quality. Overall, adherence to OSH best practices and level of development were only partially fulfilled. Conclusions Although this suboptimal performance regarding openness of designs may limit the benefits of the model, data suggests that present open-source efforts are highly beneficial and that they will be able to completely fulfill their mission given more and better OSH is carried out.

Based on the rationale that neural hypersynchronization underlies epileptic phenomena, nonperiodic stimulation (NPS) was designed and successfully tested as an electrical stimulus with robust anticonvulsant action. Considering the scale-free temporal structure of NPS mimics natural-like activity, here we hypothesized its application to the amygdala would induce minor to none impairment of neural function in treated animals. Wistar rats underwent gold-standard behavioral tests such as open field (OF), elevated plus-maze (EPM), novel object recognition, and social interaction test in order to evaluate the functions of base-level anxiety, motor function, episodic memory, and sociability. We also performed daily (8 days, 6 h per day) electrophysiological recordings (local field potential/LFP and electromyography) to assess global forebrain dynamics and the sleep-wake cycle architecture and integrity. All animals displayed an increased proportion of time exploring new objects, spent more time in the closed arms of the EPM and in the periphery of the OF arena, with similar numbers of crossing between quadrants and no significant changes of social behaviors. In the sleep-wake cycle electrophysiology experiments, we found no differences regarding duration and proportion of sleep stages and the number of transitions between stages. Finally, the power spectrum of LFP recordings and neurodynamics were also unaltered. We concluded that NPS did not impair neural functions evaluated and thus, it may be safe for clinical studies. Additionally, results corroborate the notion that NPS may exert an on-demand only desynchronization effect by efficiently competing with epileptiform activity for the physiological and healthy recruitment of neural circuitry. Considering the very dynamical nature of circuit activation and functional activity underlying neural function in general (including cognition, processing of emotion, memory acquisition, and sensorimotor integration) and its corruption leading to disorder, such mechanism of action may have important implications in the investigation of neuropsychological phenomena and also in the development of rehabilitation neurotechnology.

Electrical stimulation (ES) of the nervous system is a promising alternative for the treatment of refractory epilepsy. Based on the understanding that seizures are the expression of neural hypersynchronism, our group developed and tested a non-standard form of low-energy temporally unstructured ES termed NPS (Non-periodic stimulation), with pseudo-randomized inter-pulse intervals. Previous investigation demonstrated that NPS applied to the amygdala has a robust anticonvulsant effect against both acute and chronic seizures, and suggested that its therapeutic effect is based on direct desynchronization of ictogenic neural circuits. Further mechanistic investigation using functional magnetic resonance imaging has shown that NPS also activates nucleus accumbens (NAc) in seizure-free rats, raising the hypothesis of an alternative therapeutic mechanism: NPS-enhanced indirect inhibition / desynchronization of ictogenic circuits by NAc. In order to investigate this idea, here we evaluated behavior and cortical electrographic activity from animals submitted to pentylenetetrazole (PTZ) induced seizures, treated with NPS and with or without bilateral electrolytic lesion of NAc. NPS-treated animals with bilateral lesion of NAc expressed unexpected straub tail in addition to other stereotypical convulsive behavior, displayed increased susceptibility to PTZ (lower drug threshold), and had a much longer electrographic seizure, with a greater number of spikes, firing at a higher rate. Moreover, analysis of spike morphology showed an increase in amplitude and slope in these animals, suggesting that ablation of NAc results in disinhibition and/or increase of neural synchronism within ictogenic circuits. NPS had no therapeutic effect whatsoever in lesioned animals, while it displayed a mild anticonvulsant effect in those with intact brains. Results corroborate the notion that NAc has a key role in controlling aberrant epileptiform activity in ictogenic circuits through indirect polysynaptic connections that may enroll the ventral pallidum and ventral tegmental area. They also point to the possibility that NPS may enhance this effect, putatively by benefiting from the structure's property of detecting saliences.

Electrical Stimulation (ES) of the nervous system is a promising alternative to treat refractory epilepsy. Recent developments in the area have led to a novel method involving a non-standard form of electrical stimulation with randomized inter-pulse intervals called non-periodic stimulation (NPS). Although it is an interesting approach, there is limited statistical proof to confirm its effectiveness. Therefore this brief communication presents a survival analysis of a pre-clinical trial to assess the significance of NPS therapy. The experiment comprised four groups of rats that have been compared: two with and two without NPS treatment. ES was applied bilaterally to the amygdala in animals subjected to the pentylenetetrazole continuous infusion (10 mg/ml/min) model, myoclonic or tonic-clonic generalized seizures were triggered. The Kaplan-Meier estimator was used to develop survival functions and the Logrank test was carried out to check the differences among groups. The first comparison was made between two groups of rats that developed generalized tonic-clonic seizures (GTC groups), those who received NPS treatment took longer to develop epileptic seizures. The logrank test proved statistical difference due to reaching a p-value of 7%. The second comparison was performed between two groups of rats that developed myoclonic seizures (MYO groups), and once again better survival probabilities were observed for the NPS group. The Logrank test revealed a p-value of 0.5% thereof. Thus, a survival analysis of NPS treatment proved effectiveness against seizures by promoting an anticonvulsant effect. By comparing the groups selected for this study, it was found that the NPS treatment yielded better results, mainly against myoclonic seizures.

Epilepsy is the second most prevalent brain disorder affecting approximately 70 million people worldwide. A modern approach to developing the brain study is to model it as a system of systems, represented by a network of oscillators, in which the emergent property of synchronization occurs. Based on this perspective, epileptic seizures are processes of hyper-synchronization between brain areas. The paper develops a case study with the use of Partial Directed Coherence (PDC), Surrogate and Mutual Information (MI) to perform functional connectivity analysis observing the synchronization phenomenon. The aim is to examine the connectivity and transmission rate (R) between brain areas—cortex, hippocampus and thalamus—during basal intervals. The main contribution of this paper is the combination of both methods to study the connectivity and transmission rate between brain areas. A case study performed using 5 EEG signals from rodents showed that the applied methodology represents another appropriate alternative to existing methods for functional analysis such as Granger Causality, Transfer Entropy, providing insights on epileptic brain communication.

Purpose The purpose of this paper is to argue in favor of the open hardware philosophy (open-source hardware – OSH) as a technological innovation and academic entrepreneurshipmodel in Brazil. Design/methodology/approach This argument is based on three pillars. The first one refers to a bibliographic review of theoretical frameworks related to academic entrepreneurship and technological innovation to emphasize the disruptive innovation capacity of academia. Second, a few elements related to the Brazilian political, economic and structural scenario, which entail a (more) favorable environment to technological innovation and academic entrepreneurship, is presented. Finally, concepts related to OSH and its business model are approached to demonstrate the facilitating effect toward the whole process. Findings As a result of the argument made herein, it is possible to perceive the viability of the OSH model in terms of entrepreneurship and technological innovation in the academic sphere, and to perceive its benefits before social and economic needs in areas such as health and education. Research limitations/implications There are no empirical or quantifiable data in the literature that enable comparison between OSH and traditional technological innovation models. Originality/value The considerations on the philosophical value of OSH and its business models are scarcely explored in international literature. As far as we know, relating OSH to technological innovation entrepreneurship in the academic sphere, as well as its singularities in Brazil regarding the innovation national system and social and economic demands, is a unique approach in literature.

Studies have demonstrated the beneficial effects of light- and moderate-intensity physical exercise on the nervous system of animals with cerebral ischemia. To investigate the effects of two high-intensity physical exercise protocols, standardized for resistance and strength gain, in rats trained before cerebral ischemia induced by Bilateral Common Carotid Artery Occlusion (BCCAO). Forty-eight male Wistar rats were divided into two groups: with ischemia and without ischemia (sham). Both groups were subdivided into animals that performed high-intensity exercises in the muscle strength modality (I+Ex2; Sham+Ex2; n=16); animals submitted to high-intensity exercises in the aerobic modality (I+Ex1; Sham+Ex1; n=16), and animals that did not practice physical exercises - sedentary (I+Sed; Sham+Sed, n=16). Cerebral ischemia was induced using the BCCAO model. The physical training program used before the procedure was of high intensity, in the aerobic and muscular strength modalities, and was performed using a vertical ladder, for 4 weeks, 5 days per week. In order to process and stain the brain tissue, the Nissl method was used for neuron labeling and quantification in the cortex, striatum, and hippocampus. As for the animals' body weight and the heart weight differences were found between the groups I+Ex2 and Sham+Ex2 (p0.05). Data on neuron quantification in the cerebral cortex, dentate gyrus, and right and left striatum revealed significant differences between groups. High-intensity physical training in the strength gain modality promotes significant damage to the animal's brain when performed prior to BCCAO-induced cerebral ischemia.

The idea of the epileptic brain being highly excitable and facilitated to synchronic activity has guided pharmacological treatment since the early twentieth century. Although tackling epilepsy's seizure-prone feature, by tonically modifying overall circuit excitability and/or connectivity, the last 50 years of drug development has not seen a substantial improvement in seizure suppression of refractory epilepsies. This review presents a new conceptual framework for epilepsy in which the temporal dynamics of the disease plays a more critical role in both its understanding and therapeutic strategies. The repetitive epileptiform pattern (characteristic during ictal activity) and other well-defined electrographic signatures (i.e., present during the interictal period) are discussed in terms of the sequential activation of the circuit motifs. Lessons learned from the physiological activation of neural circuitry are used to further corroborate the argument and explore the transition from proper function to a state of instability. Furthermore, the review explores how interfering in the temporally dependent abnormal connectivity between circuits may work as a therapeutic approach. We also review the use of probing stimulation to access network connectivity and evaluate its power to determine transitional states of the dynamical system as it moves towards regions of instability, especially when conventional electrographic monitoring is proven inefficient. Unorthodox cases, with little or no scalp electrographic correlate, in which ictogenic circuitry and/or seizure spread is temporally restricted to neurovegetative, cognitive, and motivational areas are shown as possible explanations for sudden death in epilepsy (SUDEP) and other psychiatric comorbidities. In short, this review presents a paradigm shift in the way that we address the disease and is aimed to encourage debate rather than narrow the rationale epilepsy is currently engaged in. This article is part of the Special Issue “NEWroscience 2018".

Temporal lobe epileptic seizures are one of the most common and well-characterized types of epilepsies. The current knowledge on the pathology of temporal lobe epilepsy relies strongly on studies of epileptogenesis caused by experimentally induced status epilepticus (SE). Although several temporal lobe structures have been implicated in the epileptogenic process, the hippocampal formation is the temporal lobe structure studied in the greatest amount and detail. However, studies in human patients and animal models of temporal lobe epilepsy indicate that the amygdaloid complex can be also an important seizure generator, and several pathological processes have been shown in the amygdala during epileptogenesis. Therefore, in the present review, we systematically selected, organized, described, and analyzed the current knowledge on anatomopathological data associated with the amygdaloid complex during SE-induced epileptogenesis. Amygdaloid complex participation in the epileptogenic process is evidenced, among others, by alterations in energy metabolism, circulatory, and fluid regulation, neurotransmission, immediate early genes expression, tissue damage, cell suffering, inflammation, and neuroprotection. We conclude that major efforts should be made in order to include the amygdaloid complex as an important target area for evaluation in future research on SE-induced epileptogenesis. This article is part of the Special Issue “NEWroscience 2018”.

Electrical stimulation of the central nervous system is a promising alternative for the treatment of pharmacoresistant epilepsy. Successful clinical and experimental stimulation is most usually carried out as continuous trains of current or voltage pulses fired at rates of 100 Hz or above, since lower frequencies yield controversial results. On the other hand, stimulation frequency should be as low as possible, in order to maximize implant safety and battery efficiency. Moreover, the development of stimulation approaches has been largely empirical in general, while they should be engineered with the neurobiology of epilepsy in mind if a more robust, efficient, efficacious, and safe application is intended. In an attempt to reconcile evidence of therapeutic effect with the understanding of the underpinnings of epilepsy, our group has developed a nonstandard form of low-frequency stimulation with randomized interpulse intervals termed nonperiodic stimulation (NPS). The rationale was that an irregular temporal pattern would impair neural hypersynchronization, which is a hallmark of epilepsy. In this review, we start by briefly revisiting the literature on the molecular, cellular, and network level mechanisms of epileptic phenomena in order to highlight this often-overlooked emergent property of cardinal importance in the pathophysiology of the disease. We then review our own studies on the efficacy of NPS against acute and chronic experimental seizures and also on the anatomical and physiological mechanism of the method, paying special attention to the hypothesis that the lack of temporal regularity induces desynchronization. We also put forward a novel insight regarding the temporal structure of NPS that may better encompass the set of findings published by the group: the fact that intervals between stimulation pulses have a distribution that follows a power law and thus may induce natural-like activity that would compete with epileptiform discharge for the recruitment of networks. We end our discussion by mentioning ongoing research and future projects of our lab.

Epilepsy is a public health issue worldwide, given its biological, social, and economic impacts. Moreover, and particularly important, a significant portion of patients is refractory to conventional treatments and novel treatments are in need. By this token, the use and development of computational tools for the detection of epileptiform spikes, together with its feature extraction, have central significance, since these are recognized electrographic signatures of the disorder. In the present work, a detection method of such paroxysms in electroencephalographic recordings is proposed. With low mathematical complexity, the algorithm was developed for fast spike detection by using amplitude and time thresholds - both of them adjustable by the user - and applying a moving and variable amplitude threshold, calculated in each temporal window of analysis. This was done in order to provide greater adaptability to the algorithm and cope with the variable nature of epileptiform spikes. The algorithm was applied to recordings of animals submitted to acute seizures induced by a chemoconvulsant and results were compared to the visual detection of a specialist. Results showed the proposed algorithm can perform at the same level of other previously described approaches, considering the highly variable amplitude of spikes.

Non-periodic stimulation (NPS) has been shown to be an alternative to the treatment of epilepsy due to its anticonvulsant power. In this work, we analyzed the effects of NPS in the amygdalae of animals submitted to pentylenetetrazole (PTZ), a convulsant drug. We used the power spectrum density (PSD) to compare the energy bands and spectral signatures of Wistar rats under the effects of NPS, PTZ, and the use of NPS and PTZ together to characterize each of the agents and to be able to understand therapeutic mechanisms of NPS. All the animals underwent a surgical procedure for implantation of bipolar stimulation electrodes in both amygdalae and of monopolar recording electrodes in thalamus, hippocampus, and cortex. On the experiment day, NPS was applied in the amygdalae of animals in NPS and PTZ + NPS groups. In the PTZ and PTZ + NPS group, animals received a bolus injecion of PTZ (20 mg/Kg). After the experiment, energy bands for the electrophysiologic data were analyzed with Fourier transform performed in a bin with 15 min. Results showed that the spectrum of the PTZ group is deformed to lose energy at lower frequencies ( 100 Hz) when compared with the control group. Animals submitted to PTZ + NPS has a spectral signature with less changes, indicating that NPS acts in a way that forces the PTZ-changed spectrum back to its normal state. Moreover, NPS did not show any effect in the activity of a healthy brain.

Epilepsy is a brain disorder characterized by sustained predisposition to generate epileptic seizures. According to the World Health Organization, it is one of the most common neurological disorders, affecting approximately 50 million people worldwide. A modern approach for brain study is to model it as a complex system composed of a network of oscillators in which the emergent property of synchronization arises. By this token, epileptic seizures can be understood as a process of hypersynchronization between brain areas. To assess such property, Partial Directed Coherence (PDC) method represents a suitable technique, once it allows a more precise investigation of interactions that may reveal direct influences from one brain area on another. During connectivity analysis, there may be a need to assess the statistical significance of the communication threshold and Surrogate Data, a method already applied for that purpose, can be used. Hence, the objective in this work was to carry out PDC connectivity analysis in combination with Surrogate Data to evaluate the communication threshold between brain areas and develop a graph model evolution during epileptic seizure, according to the classical EEG frequency bands. The main contribution is the threshold analysis adding statistical significance for connectivity investigation. A case study performed using EEG signals from rats showed that the applied methodology represents an appropriate alternative for functional analysis, providing insights on brain communication.

Many patients with epilepsy do not obtain proper control of their seizures through conventional treatment. We review aspects of the pathophysiology underlying epileptic phenomena, with a special interest in the role of the amygdala, stressing the importance of hypersynchronism in both ictogenesis and epileptogenesis. We then review experimental studies on electrical stimulation of mesiotemporal epileptogenic areas, the amygdala included, as a means to treat medically refractory epilepsy. Regular high-frequency stimulation (HFS) commonly has anticonvulsant effects and sparse antiepileptogenic properties. On the other hand, HFS is related to acute and long-term increases in excitability related to direct neuronal activation, long-term potentiation, and kindling, raising concerns regarding its safety and jeopardizing in-depth understanding of its mechanisms. In turn, the safer regular low-frequency stimulation (LFS) has a robust antiepileptogenic effect, but its pro- or anticonvulsant effect seems to vary at random among studies. As an alternative, studies by our group on the development and investigation of temporally unstructured electrical stimulation applied to the amygdala have shown that nonperiodic stimulation (NPS), which is a nonstandard form of LFS, is capable of suppressing both acute and chronic spontaneous seizures. We hypothesize two noncompetitive mechanisms for the therapeutic role of amygdala in NPS, 1) a direct desynchronization of epileptic circuitry in the forebrain and brainstem and 2) an indirect desynchronization/inhibition through nucleus accumbens activation. We conclude by reintroducing the idea that hypersynchronism, rather than hyperexcitability, may be the key for epileptic phenomena and epilepsy treatment.

A ciencia como empreitada humana de busca do conhecimento muito se beneficiou nao so do estabelecimento do metodo cientifico, mas tambem de sua divulgacao para os pares e para o publico leigo. No fazer cientifico, portanto, entra em cena uma serie de atores para alem do cientista, incluindo o jornalista e outros mais, estando todos eles sujeitos a imprimir, nesse processo, cores de ideologias de toda natureza, inclusive politico-partidaria. Apesar de que a quantidade e a qualidade dessa influencia e discutivel, conhecer o fenomeno parece essencial. Neste artigo de opiniao, apresentamos os elementos basicos do metodo cientifico e da divulgacao cientifica, bem como as relacoes que politica e ciencia mantem, com interesse especial para aquelas que se dao na divulgacao cientifica para o publico leigo. Para isso, analisamos com mais detalhes um caso ilustrativo de influencia de ideologia politico-partidaria na divulgacao leiga da neurociencia: a repercussao na midia eletronica da demonstracao do exoesqueleto robotico na abertura da Copa do Mundo no Brasil. Concluimos com reflexoes sociologicas que situam a questao em analise em uma perspectiva que talvez coopere na importante aproximacao entre ciencia e jornalismo

Cortical areas that directly receive sensory inputs from the thalamus were long thought to be exclusively dedicated to a single modality, originating separate labeled lines. In the past decade, however, several independent lines of research have demonstrated cross-modal responses in primary sensory areas. To investigate whether these responses represent behaviorally relevant information, we carried out neuronal recordings in the primary somatosensory cortex (S1) and primary visual cortex (V1) of rats as they performed whisker-based tasks in the dark. During the free exploration of novel objects, V1 and S1 responses carried comparable amounts of information about object identity. During execution of an aperture tactile discrimination task, tactile recruitment was slower and less robust in V1 than in S1. However, V1 tactile responses correlated significantly with performance across sessions. Altogether, the results support the notion that primary sensory areas have a preference for a given modality but can engage in meaningful cross-modal processing depending on task demand.

Many patients with epilepsy do not obtain proper control of their seizures through conventional treatment. We review aspects of the pathophysiology underlying epileptic phenomena, with a special interest in the role of the amygdala, stressing the importance of hypersynchronism in both ictogenesis and epileptogenesis. We then review experimental studies on electrical stimulation of mesiotemporal epileptogenic areas, the amygdala included, as a means to treat medically refractory epilepsy. Regular high-frequency stimulation (HFS) commonly has anticonvulsant effects and sparse antiepileptogenic properties. On the other hand, HFS is related to acute and long-term increases in excitability related to direct neuronal activation, long-term potentiation, and kindling, raising concerns regarding its safety and jeopardizing in-depth understanding of its mechanisms. In turn, the safer regular low-frequency stimulation (LFS) has a robust antiepileptogenic effect, but its pro- or anticonvulsant effect seems to vary at random among studies. As an alternative, studies by our group on the development and investigation of temporally unstructured electrical stimulation applied to the amygdala have shown that nonperiodic stimulation (NPS), which is a nonstandard form of LFS, is capable of suppressing both acute and chronic spontaneous seizures. We hypothesize two noncompetitive mechanisms for the therapeutic role of amygdala in NPS, 1) a direct desynchronization of epileptic circuitry in the forebrain and brainstem and 2) an indirect desynchronization/inhibition through nucleus accumbens activation. We conclude by reintroducing the idea that hypersynchronism, rather than hyperexcitability, may be the key for epileptic phenomena and epilepsy treatment.

Electrical stimulation applied to the basolateral amygdala in the pentylenetetrazole animal model of seizures may result in either a proconvulsant or an anticonvulsant effect depending on the interpulse intervals used: periodic or nonperiodic, respectively. We tested the effect of this electrical stimulation temporal coding on the spontaneous and recurrent behavioral seizures produced in the chronic phase of the pilocarpine animal model of temporal lobe epilepsy, an experimental protocol that better mimics the human condition. After 45 days of the pilocarpine-induced status epilepticus, male Wistar rats were submitted to a surgical procedure for the implantation of a bipolar electrical stimulation electrode in the right basolateral amygdala and were allowed to recover for seven days. The animals were then placed in a glass box, and their behaviors were recorded daily on DVD for 6 h for 4 consecutive days (control period). Spontaneous recurrent behavioral seizures when showed in animals were further recorded for an extra 4-day period (treatment period), under periodic or nonperiodic electrical stimulation. The number, duration, and severity of seizures (according to the modified Racine's scale) during treatment were compared with those during the control period. The nonperiodically stimulated group displayed a significantly reduced total number and duration of seizures. There was no difference between control and treatment periods for the periodically stimulated group. Results corroborate previous findings from our group showing that nonperiodic electrical stimulation has a robust anticonvulsant property. In addition, results from the pilocarpine animal model further strengthen nonperiodic electrical stimulation as a valid therapeutic approach in current medical practice. Our working hypothesis is that temporally unstructured electrical stimulation may wield its effect by desynchronizing neural networks involved in the ictogenic process.

Our working hypothesis is that constant inter-pulse interval (IPI) electrical stimulation (ES) would resonate with endogenous epileptogenic reverberating circuits, favoring seizure, while random inter-interval ES protocol would promote desynchronization of such neural networks, interfering with the abnormal recruitment of neural structures. Male Wistar rats were stereotaxically implanted with a monopolar ES carbon-fiber electrode (minimizing fMRI artifact) in the amygdala. A 7T fMRI scanner was used to evaluate brain activity during ES, fixed four pulses per second ratio, using either a periodic IPI (ES-P) or random IPI (non-periodic ES-NP) stimulation paradigm. Appropriate imaging protocols were used to compare baseline BOLD (blood oxygen level dependent) MRI with scans during ES. A second series of experiments, both without stimuli and under the same ES paradigms, were evaluated during continuous infusion of pentylenetetrazole (PTZ, 4mg/ml/min) through an i.v. catheter. Our results show that temporal lobe activation during ES-P or ES-NP did not present any statistical differences during ES. However, during PTZ infusion, PTZ-P facilitated recruitment of the temporal lobe ipsilateral to ES while PTZ-NP showed significantly less activation ipsilateral to ES and, in turn, less inter-hemispheric differences. Altogether, our results support the hypothesis of reverberating circuits being synchronized by ES-P and desynchronized by ES-NP. Time-coded low frequency stimulation may be an interesting alternative treatment for patients with refractory epilepsy.

Our working hypothesis is that constant interpulse interval (IPI) electrical stimulation would resonate with endogenous epileptogenic reverberating circuits, inducing seizures, whereas a random interinterval electrical stimulation protocol would promote desynchronization of such neural networks, producing an anticonvulsant effect. Male Wistar rats were stereotaxically implanted with a bipolar electrical stimulation electrode in the amygdala. Pentylenetetrazole (10 mg/ml/min) was continuously infused through an intravenous catheter to induce seizures while four different patterns of temporally coded electrical stimulation were applied: periodic stimulation (PS), pseudo-randomized IPI stimulation (LH), restrictively randomized IPI stimulation (IH), and bursts of 20-ms IPIs (burst). PS decreased the pentylenetetrazole threshold to forelimb clonus, whereas IH increased the threshold to forelimb clonus and to generalized tonic–clonic seizures. We hypothesize that PS facilitates forelimb clonus by reverberating with epileptogenic circuits in the limbic system, whereas IH delays forelimb clonus and generalized tonic–clonic seizures by desynchronizing the epileptic neural networks in the forebrain–midbrain–hindbrain circuits.

Sleep is critical for hippocampus-dependent memory consolidation. However, the underlying mechanisms of synaptic plasticity are poorly understood. The central controversy is on whether long-term potentiation (LTP) takes a role during sleep and which would be its specific effect on memory. To address this question, we used immunohistochemistry to measure phosphorylation of Ca2+/calmodulin-dependent protein kinase II (pCaMKIIα) in the rat hippocampus immediately after specific sleep-wake states were interrupted. Control animals not exposed to novel objects during waking (WK) showed stable pCaMKIIα levels across the sleep-wake cycle, but animals exposed to novel objects showed a decrease during subsequent slow-wave sleep (SWS) followed by a rebound during rapid-eye-movement sleep (REM). The levels of pCaMKIIα during REM were proportional to cortical spindles near SWS/REM transitions. Based on these results, we modeled sleep-dependent LTP on a network of fully connected excitatory neurons fed with spikes recorded from the rat hippocampus across WK, SWS and REM. Sleep without LTP orderly rescaled synaptic weights to a narrow range of intermediate values. In contrast, LTP triggered near the SWS/REM transition led to marked swaps in synaptic weight ranking. To better understand the interaction between rescaling and restructuring during sleep, we implemented synaptic homeostasis and embossing in a detailed hippocampal-cortical model with both excitatory and inhibitory neurons. Synaptic homeostasis was implemented by weakening potentiation and strengthening depression, while synaptic embossing was simulated by evoking LTP on selected synapses. We observed that synaptic homeostasis facilitates controlled synaptic restructuring. The results imply a mechanism for a cognitive synergy between SWS and REM, and suggest that LTP at the SWS/REM transition critically influences the effect of sleep: Its lack determines synaptic homeostasis, its presence causes synaptic restructuring., Author Summary Sleep is important for long lasting memories. There exists, however, a controversy regarding the mechanisms by which sleep modifies synapses to consolidate enduring memories. One theory posits that sleep weakens synapses, leading to the forgetting of all but the strongest memories. The alternative theory proposes that sleep promotes both weakening and strengthening of different connections, the latter through a process known as long-term potentiation (LTP). Here we measured the levels of a phosphorylated protein related to LTP during the sleep cycle of rats and used the data to build models of sleep-dependent synaptic plasticity. By feeding one model with spikes recorded from the rat hippocampus, we observed that LTP during sleep not merely strengthens certain connections, but actually reorganizes how these connections are ranked in strength, leading to substantial changes of the overall pattern. A more detailed model of hippocampus and cortex showed that the interaction of the mechanisms predicted by the competing theories promotes a more efficient control of which memories are stored. Our results provide a step forward in the understanding of the cognitive role of sleep by indicating that the current competing theories are not mutually exclusive. Instead, each constitutes an important stage of memory consolidation.

SummaryAn important step for cholinergic transmission involves the vesicular storage of acetylcholine (ACh), a process mediated by the vesicular acetylcholine transporter (VAChT). In order to understand the physiological roles of the VAChT, we developed a genetically altered strain of mice with reduced expression of this transporter. Heterozygous and homozygous VAChT knockdown mice have a 45% and 65% decrease in VAChT protein expression, respectively. VAChT deficiency alters synaptic vesicle filling and affects ACh release. Whereas VAChT homozygous mutant mice demonstrate major neuromuscular deficits, VAChT heterozygous mice appear normal in that respect and could be used for analysis of central cholinergic function. Behavioral analyses revealed that aversive learning and memory are not altered in mutant mice; however, performance in cognitive tasks involving object and social recognition is severely impaired. These observations suggest a critical role of VAChT in the regulation of ACh release and physiological functions in the peripheral and central nervous system.

In the PTZ animal model of epilepsy, electrical stimulation applied to the amygdaloid complex may result in either pro-convulsive or anticonvulsant effect, depending on the temporal pattern used (i.e. periodic-PS and non-periodic-NPS electrical stimulation). Our hypothesis is that the anatomical target is a determinant factor for the differential effect of temporally-coded patterns on seizure outcome. The threshold dose of PTZ to elicit forelimb clonus and generalized tonic–clonic seizure behavior was measured. The effect of amygdaloid complex PS on forelimb clonus threshold showed a pro-convulsive effect while NPS was anticonvulsant. NPS also significantly increased generalized tonic–clonic threshold; while PS, although at lower threshold levels, did not present statistical significance. Thalamus stimulation did not affect forelimb clonus threshold and showed similar anticonvulsant profiles for both PS and NPS on generalized tonic–clonic threshold. In summary, the anatomical target is a determinant factor on whether temporally-coded ES differentially modulates seizure outcome.

CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Recurrent and spontaneous seizures are the hallmark of epilepsy, a neurological disease that affects around 1% of the world population and has higher incidence in developing countries. In general, seizure (or ictal) events are relatively easily identified due to their hypersynchronous and hyperexcitable nature, but the underlying neuronal mechanisms that give rise to such events are still unclear. One of the main ways of elucidating this involves the extraction of relevant features from electroencephalographic signals that are related to abnormal neuronal functioning. One promising strategy to highlight such features is the use of active probing paradigms. That is, the use of probing stimuli that would reveal information from a dynamical system, that would be otherwise inaccessible (or difficult to detect) through passive observation. This work evaluates the use of such probing strategies in two different contexts. In the first part of this thesis, a modified version of a well-known neural mass model is used to test how low-frequency probing stimuli enhance the detection of approaching seizures. We show that, as parameters are shifted to bring the model towards seizure activity, features extracted from the simulated activity reflect these changes when probing stimuli are used. Furthermore, the changes revealed by the stimuli appear to reflect the phenomenon of critical slowing down, where increased recovery times from perturbations may signal the loss of a systems’ resilience and are common hallmarks of an impending critical transition. Incorporating this strategy into early-warning systems may ultimately enable closing the loop for targeted seizure-controlling interventions. In the second part of the work, an auditory task was used to evaluate sound processing in epilepsy patients undergoing presurgical monitoring with depth electrode implants. It was hypothesized that regions involved in the onset of seizures would display abnormal auditory steady-state responses (ASSR) to amplitude-modulated sounds. This could be in the form of abnormal hypersynchronous responses in regions not usually involved in primary auditory processing, or in impaired responses due to central auditory dysfunctions caused by epileptogenic circuits. Results show that ASSRs were rarely elicited in electrode contacts within seizure onset zones (SOZ), contradicting the first hypothesis. Accurately evaluating the second hypothesis (of impaired ASSRs within SOZ) was not possible due to the highly heterogeneous nature of the data and implant schemes from all participants. This work showed the potential of low-frequency probing stimuli to highlight features and reveal underlying dynamics involved in the transition from interictal to ictal activity. However, the use of ASSRs for accurately identifying putative epileptogenic regions was limited. These responses are still promising for other diagnostics, such as identifying lateralization or seizure susceptibility, as may other types of stimuli be useful for identifying epileptogenic regions. Computational and experimental models will be crucial for defining the best strategies and parameters of active probing approaches for the identification of abnormal and epileptic activity. Crises espontâneas recorrentes são a marca registrada da epilepsia, uma doença neurológica que afeta cerca de 1% da população mundial e tem maior incidência em países em desenvolvimento. Em geral, os eventos de crise (ou ictais) são identificados com relativa facilidade devido à sua natureza hipersíncrona e hiperexcitável. Porém, os mecanismos neuronais subjacentes que dão origem a tais eventos não são totalmente esclarecidos. Uma das principais formas de elucidar isso envolve a extração de atributos relevantes de sinais eletroencefalográficos que estão relacionados ao funcionamento neuronal anormal. Uma estratégia promissora para ressaltar e auxiliar na identificação desses atributos é o uso de paradigmas de sondagem ativa. Ou seja, estímulos de sondagem revelariam informações de sistemas neurais, que seriam inacessíveis (ou difíceis de detectar) por meio da observação passiva. Este trabalho avalia o uso de tais estratégias de sondagem em dois contextos diferentes. Na primeira parte desta tese, uma versão modificada de um conhecido modelo de massa neural é usada para testar como estímulos de sondagem de baixa frequência auxiliam na identificação de estados com alta suscetibilidade a crises. Mostramos que, conforme os parâmetros são alterados para trazer o modelo para a atividade ictal, os atributos extraídos da atividade neural simulada refletem essas mudanças quando os estímulos de sondagem são usados. Além disso, as mudanças reveladas pelos estímulos refletem o fenômeno de desaceleração crítica, no qual há um aumento nos tempos de recuperação a perturbações. Isso sinalizaria a perda de resiliência de um sistema e é uma marca comum de uma transição crítica iminente. A incorporação do método aqui avaliado em sistemas de previsão de crises poderia permitir o fechamento da malha de um sistema de intervenções para controle de crises. Na segunda parte do trabalho, uma tarefa auditiva foi utilizada para avaliar o processamento auditivo em pacientes com epilepsia submetidos à monitorização invasiva pré-cirúrgica, com registros de estereoeletroencefalografia (SEEG). Partimos da hipótese que as regiões envolvidas no início das crises exibiriam potenciais evocados auditivos em regime permanente (PEARP, ou ASSR) anormais a sons modulados em amplitude (AM). Ou seja, circuitos epileptogêncicos influenciariam a resposta oscilatória induzida por sons AM. Esse efeito poderia ser (i) na forma de respostas hipersíncronas anormais em regiões que geralmente não estão envolvidas no processamento deste tipo de estímulo, ou (ii) em respostas comprometidas caso os circuitos epileptogênicos prejudicassem o processamento auditivo central. Os resultados mostram que os PEARPs raramente foram observados em contatos dos eletrodos nas zonas de início das crises, contradizendo a primeira hipótese. Avaliar com precisão a segunda hipótese (de diminuição de PEARPs dentro de circuitos epileptogênicos) não foi possível devido à natureza altamente heterogênea dos dados e da grande variabilidade nos esquemas de implantes de todos os pacientes. Este trabalho mostrou o potencial dos estímulos de sondagem de baixa frequência para ressaltar atributos eletrográficos e revelar dinâmicas envolvidas na transição da atividade neural de estados interictais para ictais. No entanto, o uso de PEARPs para identificar com precisão as regiões epileptogênicas foi limitado. Esses tipos de respostas auditivas ainda são promissores para outros diagnósticos, como a identificação de lateralização ou susceptibilidade a crises, assim como outros tipos de estímulos podem ser úteis para identificar regiões epileptogênicas. Modelos computacionais e experimentais serão cruciais para definir as melhores estratégias e parâmetros de abordagens de sondagem ativa para a identificação de atividade anormal e epiléptica.

CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Até 80% dos pacientes com epilepsia do lobo temporal (TLE) não respondem adequadamente aos anticonvulsivantes e nos últimos trinta anos houve poucos avanços no tratamento farmacológico, de forma que se faz necessária nova forma de abordagem no estudo das epilepsias. Atualmente, entende-se a epilepsia como um desbalanço entre excitação e inibição e, recentemente, o hipersincronismo entre redes neurais na presença ou não desse desbalanço tem se mostrado uma nova forma de entender os motivos que predispõe o cérebro a desenvolver epilepsia. Neste trabalho foi utilizada a resposta auditiva evocada em regime permanente (ASSR) para avaliar o hipersincronismo entre redes neurais e as alterações de processamento cerebral que ocorrem em modelo animal de epilepsia do lobo temporal, utilizando ácido kaínico (KA) intrahipocampal. Foi demonstrado que há aumento do sincronismo entre as áreas estudadas (hipocampo, amígdala e colículo inferior) de forma progressiva no processo de epileptogênese, principalmente ipsilateral à injeção de KA em CA3 direito, além de alteração do processamento auditivo cerebral e da modulação de cima para baixo. Essas alterações mostram que mesmo lesões mais rostrais como a realizada no hipocampo são capazes de alterar o processamento sensorial primário do cérebro de estruturas mais caudais como o colículo inferior. Dessa forma, a ASSR mostrou que na TLE os animais apresentam um comprometimento do processamento cerebral de estruturas não diretamente envolvidas neste tipo de epilepsia. As alterações do processamento cerebral mostradas no presente trabalho são mais profundas do que anteriormente mostradas na literatura e poderiam ser responsáveis pelas comorbidades encontradas em pacientes epilépticos como, por exemplo, os distúrbios psiquiátricos que são mais frequentes nesta população. O hipersincronismo entre redes neurais encontrado neste trabalho e em outros trabalhos com diferentes tipos de epilepsia permite inferir que, caso o hipersincronismo seja uma propriedade geral das epilepsias, pode ser utilizado como um novo alvo terapêutico, e a ASSR como possível ferramenta de auxílio diagnóstico. Além disso, este trabalho mostrou que a ASSR tem potencial de auxiliar no diagnóstico da lateralidade da crise por apresentar diferentes respostas, dependendo do hemisfério inicialmente acometido. Assim, novos estudos são necessários para avaliar o hipersincronismo em outros tipos de epilepsia além da replicação dos resultados em pacientes com TLE. Two thirds of patients with temporal lobe epilepsy (TLE) do not respond adequately to anticonvulsants and in the past thirty years there has been little progress in pharmacological treatment, so a new approach is needed in the epilepsies study. Currently, epilepsy is understood as an imbalance between excitation and inhibition and recently the hyper synchronism between neural networks in the presence or not of this imbalance has been shown to be a new way of understanding the reasons that predispose the brain to epilepsy development. In this work, the auditory steady-state-evoked response (ASSR) was used to assess the hyper-synchronism between neural networks and the changes in brain processing that occur in an animal model of temporal lobe epilepsy with intrahypocampal kainic acid (KA) injection. It has been demonstrated that there is an increase in the synchronism between the studied areas (hippocampus, amygdala and inferior colliculus) progressively in the process of epileptogenesis, mainly ipsilateral to the injection of KA in right CA3, in addition to impairment of the brain auditory processing and of top-down modulation. These changes show that even more rostral lesions such as the one performed in the hippocampus are capable of changing the brain's primary sensory processing of more caudal structures such as the inferior colliculus. Thus, ASSR showed that animals in TLE have impaired brain processing of structures not directly involved in this type of epilepsy. The changes in brain processing shown in the present study are more profound than previously shown in the literature and could be responsible for the comorbidities found in epileptic patients, such as the psychiatric disorders that are more frequent in this population. The hyper synchronism between neural networks found in this work and in other works with different types of epilepsy allows us to infer that hyper synchronism may be a general property of epilepsies and so it may be used as a new therapeutic target, and ASSR as a possible diagnostic aid tool. In addition, this study showed that ASSR has the potential to help diagnose the laterality of the crisis by presenting different responses, depending on the hemisphere initially affected. Thus, further studies are needed to assess hyper-synchronism in other types of epilepsy in addition to the replication of results in patients with TLE.

Structure learning of Bayesian Networks (BNs) is an NP-hard problem, and the use of sub-optimal strategies is essential in domains involving many variables. One of them is to generate multiple approximate structures and then to reduce the ensemble to a representative structure. It is possible to use the occurrence frequency (on the structures ensemble) as the criteria for accepting a dominant directed edge between two nodes and thus obtaining the single structure. In this doctoral research, it was made an analogy with an adapted one-dimensional random-walk for analytically deducing an appropriate decision threshold to such occurrence frequency. The obtained closed-form expression has been validated across benchmark datasets applying the Matthews Correlation Coefficient as the performance metric. In the experiments using a recent medical dataset, the BN resulting from the analytical cutoff-frequency captured the expected associations among nodes and also achieved better prediction performance than the BNs learned with neighbours thresholds to the computed. In literature, the feature accounted along of the perturbed structures has been the edges and not the directed edges (arcs) as in this thesis. That modified strategy still was applied to an elderly dataset to identify potential relationships between variables of medical interest but using an increased threshold instead of the predict by the proposed formula - such prudence is due to the possible social implications of the finding. The motivation behind such an application is that in spite of the proportion of elderly individuals in the population has increased substantially in the last few decades, the risk factors that should be managed in advance to ensure a natural process of mental decline due to ageing remain unknown. In the learned structural model, it was graphically investigated the probabilistic dependence mechanism between two variables of medical interest: the suspected risk factor known as Metabolic Syndrome and the indicator of mental decline referred to as Cognitive Impairment. In this investigation, the concept known in the context of BNs as D-separation has been employed. Results of the carried out study revealed that the dependence between Metabolic Syndrome and Cognitive Variables indeed exists and depends on both Body Mass Index and age. O aprendizado da estrutura de uma Rede Bayesiana (BN) é um problema NP-difícil, e o uso de estratégias sub-ótimas é essencial em domínios que envolvem muitas variáveis. Uma delas consiste em gerar várias estruturas aproximadas e depois reduzir o conjunto a uma estrutura representativa. É possível usar a frequência de ocorrência (no conjunto de estruturas) como critério para aceitar um arco dominante entre dois nós e assim obter essa estrutura única. Nesta pesquisa de doutorado, foi feita uma analogia com um passeio aleatório unidimensional adaptado para deduzir analiticamente um limiar de decisão apropriado para essa frequência de ocorrência. A expressão de forma fechada obtida foi validada usando bases de dados de referência e aplicando o Coeficiente de Correlação de Matthews como métrica de desempenho. Nos experimentos utilizando dados médicos recentes, a BN resultante da frequência de corte analítica capturou as associações esperadas entre os nós e também obteve melhor desempenho de predição do que as BNs aprendidas com limiares vizinhos ao calculado. Na literatura, a característica contabilizada ao longo das estruturas perturbadas tem sido as arestas e não as arestas direcionadas (arcos) como nesta tese. Essa estratégia modificada ainda foi aplicada a um conjunto de dados de idosos para identificar potenciais relações entre variáveis de interesse médico, mas usando um limiar aumentado em vez do previsto pela fórmula proposta - essa cautela deve-se às possíveis implicações sociais do achado. A motivação por trás dessa aplicação é que, apesar da proporção de idosos na população ter aumentado substancialmente nas últimas décadas, os fatores de risco que devem ser controlados com antecedência para garantir um processo natural de declínio mental devido ao envelhecimento permanecem desconhecidos. No modelo estrutural aprendido, investigou-se graficamente o mecanismo de dependência probabilística entre duas variáveis de interesse médico: o fator de risco suspeito conhecido como Síndrome Metabólica e o indicador de declínio mental denominado Comprometimento Cognitivo. Nessa investigação, empregou-se o conceito conhecido no contexto de BNs como D-separação. Esse estudo revelou que a dependência entre Síndrome Metabólica e Variáveis Cognitivas de fato existe e depende tanto do Índice de Massa Corporal quanto da idade.