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Osmotic transport devices (OTDs) are forward osmosis membrane devices that we recently developed to remove accumulated fluid from swollen tissue, in-vivo, under severe conditions. As such, the relative volume of the fluid required to be removed and the volumetric flowrate may be two orders of magnitude less than the operating volume and tangential flowrate of the device. This makes it challenging to measure the rate of fluid flow from the swollen tissue. Here, we introduce a differential densimetry method for determining ultra-low volumetric flux through tissue samples. This technique uses two vibrating tube density sensors, one placed upstream of the membrane in contact with the tissue sample, and one placed downstream. Any flow of biological fluid withdrawn through the tissue will combine with the OTD operating fluid resulting in an observed density shift in the second density sensor. By measuring the difference in density between the upstream and downstream fluids, one can calculate the amount of fluid flowing across the tissue with a relatively high level of sensitivity. This method is also relatively insensitive to drift from temperature fluctuations and capable of continuously monitoring tissue permeability in real time. As a proof of concept, we used this technique to measure fluid flow across ex-vivo rat spinal tissue for an appropriately scaled OTD. The repeatability error had a maximum of only 12%. This implies that this method can provide highly acceptable flux measurements with reasonable reproducibility in real-time applications of fluid removal in-vivo.

Autism Spectrum Disorders (ASD) encompass a wide array of debilitating symptoms, including severe sensory deficits and abnormal language development. Sensory deficits early in development may lead to broader symptomatology in adolescents and adults. The mechanistic links between ASD risk genes, sensory processing and language impairment are unclear. There is also a sex bias in ASD diagnosis and symptomatology. The current study aims to identify the developmental trajectory and genotype- and sex-dependent differences in auditory sensitivity and temporal processing in a Pten-deletion (phosphatase and tensin homolog missing on chromosome 10) mouse model of ASD. Auditory temporal processing is crucial for speech recognition and language development and deficits will cause language impairments. However, very little is known about the development of temporal processing in ASD animal models, and if there are sex differences. To address this major gap, we recorded epidural electroencephalography (EEG) signals from the frontal (FC) and auditory (AC) cortex in developing and adult Nse-cre PTEN mice, in which Pten is deleted in specific cortical layers (layers III-V) (PTEN conditional knock-out (cKO). We quantified resting EEG spectral power distribution, auditory event related potentials (ERP) and temporal processing from awake and freely moving male and female mice. Temporal processing is measured using a gap-in-noise-ASSR (auditory steady state response) stimulus paradigm. The experimental manipulation of gap duration and modulation depth allows us to measure cortical entrainment to rapid gaps in sounds. Temporal processing was quantified using inter-trial phase clustering (ITPC) values that account for phase consistency across trials. The results show genotype differences in resting power distribution in PTEN cKO mice throughout development. Male and female cKO mice have significantly increased beta power but decreased high frequency oscillations in the AC and FC. Both male and female PTEN cKO mice show diminished ITPC in their gap-ASSR responses in the AC and FC compared to control mice. Overall, deficits become more prominent in adult (p60) mice, with cKO mice having significantly increased sound evoked power and decreased ITPC compared to controls. While both male and female cKO mice demonstrated severe temporal processing deficits across development, female cKO mice showed increased hypersensitivity compared to males, reflected as increased N1 and P2 amplitudes. These data identify a number of novel sensory processing deficits in a PTEN-ASD mouse model that are present from an early age. Abnormal temporal processing and hypersensitive responses may contribute to abnormal development of language function in ASD., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests. Razak KA reports financial support was provided by National Institutes of Health. Huber KM reports financial support was provided by National Institutes of Health. Binder DK reports financial support was provided by National Institutes of Health. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Fragile X Syndrome (FXS) is a leading known genetic cause of intellectual disability with symptoms that include increased anxiety and social and sensory processing deficits. Recent electroencephalographic (EEG) studies in humans with FXS have identified neural oscillation deficits that include increased resting state gamma power, increased amplitude of auditory evoked potentials, and reduced phase locking of sound-evoked gamma oscillations. Similar EEG phenotypes are present in mouse models of FXS, but very little is known about the development of such abnormal responses. In the current study, we employed a 30-channel mouse multielectrode array (MEA) system to record and analyze resting and stimulus-evoked EEG signals in male P21 and P91 WT and Fmr1 KO mice. This led to several novel findings. First, P91, but not P21, Fmr1 KO mice have significantly increased resting EEG power in the low- and high-gamma frequency bands. Second, both P21 and P91 Fmr1 KO mice have markedly attenuated inter-trial phase coherence (ITPC) to spectrotemporally dynamic auditory stimuli as well as to 40 Hz and 80 Hz auditory steady-state response (ASSR) stimuli. This suggests abnormal temporal processing from early development that may lead to abnormal speech and language function in FXS. Third, we found hemispheric asymmetry of fast temporal processing in the mouse auditory cortex in WT but not Fmr1 KO mice. Together, these findings define a set of EEG phenotypes in young and adult mice that can serve as translational targets for genetic and pharmacological manipulation in phenotypic rescue studies., Competing Interests: Declaration of competing interest We report no conflicts of interest., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Autism spectrum disorders (ASD) encompass a wide array of debilitating symptoms, including sensory dysfunction and delayed language development. Auditory temporal processing is crucial for speech perception and language development. Abnormal development of temporal processing may account for the language impairments associated with ASD. Very little is known about the development of temporal processing in any animal model of ASD., Methods: In the current study, we quantify auditory temporal processing throughout development in the Fmr1 knock-out (KO) mouse model of Fragile X Syndrome (FXS), a leading genetic cause of intellectual disability and ASD-associated behaviors. Using epidural electrodes in awake and freely moving wildtype (WT) and KO mice, we recorded auditory event related potentials (ERP) and auditory temporal processing with a gap-in-noise auditory steady state response (gap-ASSR) paradigm. Mice were recorded at three different ages in a cross sectional design: postnatal (p)21, p30 and p60. Recordings were obtained from both auditory and frontal cortices. The gap-ASSR requires underlying neural generators to synchronize responses to gaps of different widths embedded in noise, providing an objective measure of temporal processing across genotypes and age groups., Results: We present evidence that the frontal, but not auditory, cortex shows significant temporal processing deficits at p21 and p30, with poor ability to phase lock to rapid gaps in noise. Temporal processing was similar in both genotypes in adult mice. ERP amplitudes were larger in Fmr1 KO mice in both auditory and frontal cortex, consistent with ERP data in humans with FXS., Conclusions: These data indicate cortical region-specific delays in temporal processing development in Fmr1 KO mice. Developmental delays in the ability of frontal cortex to follow rapid changes in sounds may shape language delays in FXS, and more broadly in ASD., (© 2023. The Author(s).)

Edema formation following traumatic spinal cord injury (SCI) exacerbates secondary injury, and the severity of edema correlates with worse neurological outcome in human patients. To date, there are no effective treatments to directly resolve edema within the spinal cord. The aquaporin-4 (AQP4) water channel is found on plasma membranes of astrocytic endfeet in direct contact with blood vessels, the glia limitans in contact with the cerebrospinal fluid, and ependyma around the central canal. Local expression at these tissue-fluid interfaces allows AQP4 channels to play an important role in the bidirectional regulation of water homeostasis under normal conditions and following trauma. In this review, we consider the available evidence regarding the potential role of AQP4 in edema after SCI. Although more work remains to be carried out, the overall evidence indicates a critical role for AQP4 channels in edema formation and resolution following SCI and the therapeutic potential of AQP4 modulation in edema resolution and functional recovery. Further work to elucidate the expression and subcellular localization of AQP4 during specific phases after SCI will inform the therapeutic modulation of AQP4 for the optimization of histological and neurological outcomes.

Volume-regulated anion channels (VRACs) are a group of ubiquitously expressed outwardly-rectifying anion channels that sense increases in cell volume and act to return cells to baseline volume through an efflux of anions and organic osmolytes, including glutamate. Because cell swelling, increased extracellular glutamate levels, and reduction of the brain extracellular space (ECS) all occur during seizure generation, we set out to determine whether VRACs are dysregulated throughout mesial temporal lobe epilepsy (MTLE), the most common form of adult epilepsy. To accomplish this, we employed the IHKA experimental model of MTLE, and probed for the expression of LRRC8A, the essential pore-forming VRAC subunit, at acute, early-, mid-, and late-epileptogenic time points (1-, 7-, 14-, and 30-days post-IHKA, respectively). Western blot analysis revealed the upregulation of total dorsal hippocampal LRRC8A 14-days post-IHKA in both the ipsilateral and contralateral hippocampus. Immunohistochemical analyses showed an increased LRRC8A signal 7-days post-IHKA in both the ipsilateral and contralateral hippocampus, along with layer-specific changes 1-, 7-, and 30-days post-IHKA bilaterally. LRRC8A upregulation 1 day post-IHKA was observed primarily in astrocytes; however, some upregulation was also observed in neurons. Glutamate-GABA/glutamine cycle enzymes glutamic acid decarboxylase, glutaminase, and glutamine synthetase were also dysregulated at the 7-day timepoint post status epilepticus. The timepoint-dependent upregulation of total hippocampal LRRC8A and the possible subsequent increased efflux of glutamate in the epileptic hippocampus suggest that the dysregulation of astrocytic VRAC may play an important role in the development of epilepsy.

Background: Fragile X syndrome (FXS) is the most common inherited form of neurodevelopmental disability. It is often characterized, especially in males, by intellectual disability, anxiety, repetitive behavior, social communication deficits, delayed language development, and abnormal sensory processing. Recently, we identified electroencephalographic (EEG) biomarkers that are conserved between the mouse model of FXS (Fmr1 KO mice) and humans with FXS., Methods: In this report, we evaluate small molecule target engagement utilizing multielectrode array electrophysiology in the Fmr1 KO mouse and in humans with FXS. Neurophysiologic target engagement was evaluated using single doses of the GABA B selective agonist racemic baclofen (RBAC)., Results: In Fmr1 KO mice and in humans with FXS, baclofen use was associated with suppression of elevated gamma power and increase in low-frequency power at rest. In the Fmr1 KO mice, a baclofen-associated improvement in auditory chirp synchronization was also noted., Conclusions: Overall, we noted synchronized target engagement of RBAC on resting state electrophysiology, in particular the reduction of aberrant high frequency gamma activity, across species in FXS. This finding holds promise for translational medicine approaches to drug development for FXS, synchronizing treatment study across species using well-established EEG biological markers in this field., Trial Registration: The human experiments are registered under NCT02998151., (© 2022. The Author(s).)

Volume Regulated Anion Channels (VRAC) are critical contributors to cell volume homeostasis and are expressed ubiquitously in all vertebrate cells. VRAC sense increases in cell volume, and act to return cells to baseline volume in a process known as regulatory volume decrease (RVD) through the efflux of anions and organic osmolytes. This review will highlight seminal studies that elucidated the role of VRAC in RVD, their characteristics as a function of subunit specificity, and their clinical relevance in physiology and pathology. VRAC are also known as volume-sensitive outward rectifiers (VSOR) and volume-sensitive organic osmolyte/anion channels (VSOAC). In this review, the term VRAC will be used to refer to this family of channels., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Ghouli, Fiacco and Binder.)

The International League Against Epilepsy/American Epilepsy Society (ILAE/AES) Joint Translational Task Force initiated the TASK3 working group to create common data elements (CDEs) for various aspects of preclinical epilepsy research studies, which could help improve the standardization of experimental designs. This article addresses neuropathological changes associated with seizures and epilepsy in rodent models of epilepsy. We discuss CDEs for histopathological parameters for neurodegeneration, changes in astrocyte morphology and function, mechanisms of inflammation, and changes in the blood-brain barrier and myelin/oligodendrocytes resulting from recurrent seizures in rats and mice. We provide detailed CDE tables and case report forms (CRFs), and with this companion manuscript, we discuss the rationale and methodological aspects of individual neuropathological examinations. The CDEs, CRFs, and companion paper are available to all researchers, and their use will benefit the harmonization and comparability of translational preclinical epilepsy research. The ultimate hope is to facilitate the development of rational therapy concepts for treating epilepsies, seizures, and comorbidities and the development of biomarkers assessing the pathological state of the disease., (© 2022 The Authors. Epilepsia Open published by Wiley Periodicals LLC on behalf of International League Against Epilepsy.)

Fragile X Syndrome (FXS) is a monogenetic form of intellectual disability and autism in which well-established knockout (KO) animal models point to neuronal hyperexcitability and abnormal gamma-frequency physiology as a basis for key disorder features. Translating these findings into patients may identify tractable treatment targets. Using source modeling of resting-state electroencephalography data, we report findings in FXS, including 1) increases in localized gamma activity, 2) pervasive changes of theta/alpha activity, indicative of disrupted thalamocortical modulation coupled with elevated gamma power, 3) stepwise moderation of low and high-frequency abnormalities based on female sex, and 4) relationship of this physiology to intellectual disability and neuropsychiatric symptoms. Our observations extend findings in Fmr1 -/- KO mice to patients with FXS and raise a key role for disrupted thalamocortical modulation in local hyperexcitability. This systems-level mechanism has received limited preclinical attention but has implications for understanding fundamental disease mechanisms., (© 2022. The Author(s).)

There has been a long history of lesioning procedures to treat tremor associated with both essential tremor (ET) and Parkinson's disease (PD). These include radiofrequency (RF) thalamotomy, gamma knife radiosurgical (GKRS) thalamotomy, and magnetic resonance-guided focused ultrasound (MRgFUS). In this review, we summarize the clinical studies of lesioning procedures for tremor focusing on these ablative therapies for ET and tremor-predominant PD (TDPD). We then consider clinical treatment variables that influence decision-making regarding ablative therapies versus consideration of deep brain stimulation (DBS) and conclude with ongoing and future studies. This article is part of the Special Issue "Tremor" edited by Daniel D. Truong, Mark Hallett, and Aasef Shaikh., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy. Dysregulation of glutamate transporters has been a common finding across animal models of epilepsy and in patients with TLE. In this study, we investigate NRG-1/ErbB4 signaling in epileptogenesis and the neuroprotective effects of NRG-1 treatment in a mouse model of temporal lobe epilepsy. Using immunohistochemistry, we report the first evidence for NRG-1/ErbB4-dependent selective upregulation of glutamate transporter EAAC1 and bihemispheric neuroprotection by exogeneous NRG-1 in the intrahippocampal kainic acid (IHKA) model of TLE. Our findings provide evidence that dysregulation of glutamate transporter EAAC1 contributes to the development of epilepsy and can be therapeutically targeted to reduce neuronal death following IHKA-induced status epilepticus (SE)., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Individuals with Fragile X syndrome (FXS) and autism spectrum disorder (ASD) exhibit an array of symptoms, including sociability deficits, increased anxiety, hyperactivity, and sensory hyperexcitability. It is unclear how endocannabinoid (eCB) modulation can be targeted to alleviate neurophysiological abnormalities in FXS as behavioral research reveals benefits to inhibiting cannabinoid (CB) receptor activation and increasing endocannabinoid ligand levels. Here, we hypothesize that enhancement of 2-arachidonoyl-sn-glycerol (2-AG) in Fragile X mental retardation 1 gene knock-out (Fmr1 KO) mice may reduce cortical hyperexcitability and behavioral abnormalities observed in FXS., Methods: To test whether an increase in 2-AG levels normalized cortical responses in a mouse model of FXS, animals were subjected to electroencephalography (EEG) recording and behavioral assessment following treatment with JZL-184, an irreversible inhibitor of monoacylglycerol lipase (MAGL). Assessment of 2-AG was performed using lipidomic analysis in conjunction with various doses and time points post-administration of JZL-184. Baseline electrocortical activity and evoked responses to sound stimuli were measured using a 30-channel multielectrode array (MEA) in adult male mice before, 4 h, and 1 day post-intraperitoneal injection of JZL-184 or vehicle. Behavior assessment was done using the open field and elevated plus maze 4 h post-treatment., Results: Lipidomic analysis showed that 8 mg/kg JZL-184 significantly increased the levels of 2-AG in the auditory cortex of both Fmr1 KO and WT mice 4 h post-treatment compared to vehicle controls. EEG recordings revealed a reduction in the abnormally enhanced baseline gamma-band power in Fmr1 KO mice and significantly improved evoked synchronization to auditory stimuli in the gamma-band range post-JZL-184 treatment. JZL-184 treatment also ameliorated anxiety-like and hyperactivity phenotypes in Fmr1 KO mice., Conclusions: Overall, these results indicate that increasing 2-AG levels may serve as a potential therapeutic approach to normalize cortical responses and improve behavioral outcomes in FXS and possibly other ASDs., (© 2021. The Author(s).)

The mechanisms underlying the common association between autism spectrum disorders (ASD) and sensory processing disorders (SPD) are unclear, and treatment options to reduce atypical sensory processing are limited. Fragile X Syndrome (FXS) is a leading genetic cause of intellectual disability and ASD behaviors. As in most children with ASD, atypical sensory processing is a common symptom in FXS, frequently manifesting as sensory hypersensitivity. Auditory hypersensitivity is a highly debilitating condition in FXS that may lead to language delays, social anxiety and ritualized repetitive behaviors. Animal models of FXS, including Fmr1 knock out (KO) mouse, also show auditory hypersensitivity, providing a translation relevant platform to study underlying pathophysiological mechanisms. The focus of this review is to summarize recent studies in the Fmr1 KO mouse that identified neural correlates of auditory hypersensitivity. We review results of electroencephalography (EEG) recordings in the Fmr1 KO mice and highlight EEG phenotypes that are remarkably similar to EEG findings in humans with FXS. The EEG phenotypes associated with the loss of FMRP include enhanced resting EEG gamma band power, reduced cross frequency coupling, reduced sound-evoked synchrony of neural responses at gamma band frequencies, increased event-related potential amplitudes, reduced habituation of neural responses and increased non-phase locked power. In addition, we highlight the postnatal period when the EEG phenotypes develop and show a strong association of the phenotypes with enhanced matrix-metalloproteinase-9 (MMP-9) activity, abnormal development of parvalbumin (PV)-expressing inhibitory interneurons and reduced formation of specialized extracellular matrix structures called perineuronal nets (PNNs). Finally, we discuss how dysfunctions of inhibitory PV interneurons may contribute to cortical hyperexcitability and EEG abnormalities observed in FXS. Taken together, the studies reviewed here indicate that EEG recordings can be utilized in both pre-clinical studies and clinical trials, while at the same time, used to identify cellular and circuit mechanisms of dysfunction in FXS. New therapeutic approaches that reduce MMP-9 activity and restore functions of PV interneurons may succeed in reducing FXS sensory symptoms. Future studies should examine long-lasting benefits of developmental vs. adult interventions on sensory phenotypes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Razak, Binder and Ethell.)

Changes in astrocyte channels, transporters, and metabolism play a critical role in seizure generation and epilepsy. In particular, alterations in astrocyte potassium, glutamate, water and adenosine homeostasis and gap junctional coupling have all been associated with hyperexcitability and epileptogenesis (largely in temporal lobe epilepsy). Distinct astrocytic changes have also been identified in other types of epilepsy, such as tuberous sclerosis, tumor-associated epilepsy and post-traumatic epilepsy. Together, the emerging literature on astrocytes and epilepsy provides powerful rationale for distinct new therapeutic targets that are astrocyte-specific., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature.)

Astrocytic glutamate transporters are crucial for glutamate homeostasis in the brain, and dysregulation of these transporters can contribute to the development of epilepsy. Glutamate transporter-1 (GLT-1) is responsible for the majority of glutamate uptake in the dorsal forebrain and has been shown to be reduced at epileptic foci in patients and preclinical models of temporal lobe epilepsy (TLE). Current antiepileptic drugs (AEDs) work primarily by targeting neurons directly through suppression of excitatory neurotransmission or enhancement of inhibitory neurotransmission, which can lead to both behavioral and psychiatric side effects. This study investigates the therapeutic capacity of astrocyte-specific AAV-mediated GLT-1 expression in the intrahippocampal kainic acid (IHKA) model of TLE. In this study, we used Western blot analysis, immunohistochemistry, and long-term-video EEG monitoring to demonstrate that cell-type-specific upregulation of GLT-1 in astrocytes is neuroprotective at early time points during epileptogenesis, reduces seizure frequency and total time spent in seizures, and eliminates large behavioral seizures in the IHKA model of epilepsy. Our findings suggest that targeting glutamate uptake is a promising therapeutic strategy for the treatment of epilepsy., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

Fragile X syndrome (FXS) is a genetic neurodevelopmental syndrome characterized by increased anxiety, repetitive behaviors, social communication deficits, delayed language development, and abnormal sensory processing. Recently, we have identified electroencephalographic (EEG) biomarkers that are conserved between the mouse model of FXS (Fmr1 KO mice) and humans with FXS. In this study, we test a specific candidate mechanism for engagement of multielectrode array (MEA) EEG biomarkers in the FXS mouse model. We administered TAK-063, a potent, selective, and orally active phosphodiesterase 10A (PDE10A) inhibitor, to Fmr1 KO mice, and examined its effects on MEA EEG biomarkers. We demonstrate significant dose-related amelioration of inter-trial phase coherence (ITPC) to temporally modulated auditory stimuli by TAK-063 in Fmr1 KO mice. Our data suggest that TAK-063 improves cortical auditory stimulus processing in Fmr1 KO mice, without significantly depressing baseline EEG power or causing any noticeable sedation or behavioral side effects. Thus, the PDE10A inhibitor TAK-063 has salutary effects on normalizing EEG biomarkers in a mouse model of FXS and should be pursued in further translational treatment development., (© 2021. The American Society for Experimental NeuroTherapeutics, Inc.)

Individuals with Fragile X Syndrome (FXS) and autism spectrum disorder (ASD) exhibit cognitive impairments, social deficits, increased anxiety, and sensory hyperexcitability. Previously, we showed that elevated levels of matrix metalloproteinase-9 (MMP-9) may contribute to abnormal development of parvalbumin (PV) interneurons and perineuronal nets (PNNs) in the developing auditory cortex (AC) of Fmr1 knock-out (KO) mice, which likely underlie auditory hypersensitivity. Thus, MMP-9 may serve as a potential target for treatment of auditory hypersensitivity in FXS. Here, we used the MMP-2/9 inhibitor, SB-3CT, to pharmacologically inhibit MMP-9 activity during a specific developmental period and to test whether inhibition of MMP-9 activity reverses neural oscillation deficits and behavioral impairments by enhancing PNN formation around PV cells in Fmr1 KO mice. Electroencephalography (EEG) was used to measure resting state and sound-evoked electrocortical activity in auditory and frontal cortices of postnatal day (P)22-23 male mice before and one-day after treatment with SB-3CT (25 mg/kg) or vehicle. At P27-28, animal behaviors were tested to measure the effects of the treatment on anxiety and hyperactivity. Results show that acute inhibition of MMP-9 activity improved evoked synchronization to auditory stimuli and ameliorated mouse behavioral deficits. MMP-9 inhibition enhanced PNN formation, increased PV levels and TrkB phosphorylation yet reduced Akt phosphorylation in the AC of Fmr1 KO mice. Our results show that MMP-9 inhibition during early postnatal development is beneficial in reducing some auditory processing deficits in the FXS mouse model and may serve as a candidate therapeutic for reversing sensory hypersensitivity in FXS and possibly other ASDs., (© 2020 International Society for Neurochemistry.)

Astrocytes regulate and respond to extracellular glutamate levels in the central nervous system (CNS) via the Na + -dependent glutamate transporters glutamate transporter-1 (GLT-1) and glutamate aspartate transporter (GLAST) and the metabotropic glutamate receptors (mGluR) 3 and mGluR5. Both impaired astrocytic glutamate clearance and changes in metabotropic glutamate signaling could contribute to the development of epilepsy. Dysregulation of astrocytic glutamate transporters, GLT-1 and GLAST, is a common finding across patients and preclinical seizure models. Astrocytic metabotropic glutamate receptors, particularly mGluR5, have been shown to be dysregulated in both humans and animal models of temporal lobe epilepsy (TLE). In this review, we synthesize the available evidence regarding astrocytic glutamate homeostasis and astrocytic mGluRs in the development of epilepsy. Modulation of astrocyte glutamate uptake and/or mGluR activation could lead to novel glial therapeutics for epilepsy., (Copyright © 2020 Peterson and Binder.)

Fragile X Syndrome (FXS) is a leading known genetic cause of intellectual disability. Many symptoms of FXS overlap with those in autism including repetitive behaviors, language delays, anxiety, social impairments and sensory processing deficits. Electroencephalogram (EEG) recordings from humans with FXS and an animal model, the Fmr1 knockout (KO) mouse, show remarkably similar phenotypes suggesting that EEG phenotypes can serve as biomarkers for developing treatments. This includes enhanced resting gamma band power and sound evoked total power, and reduced fidelity of temporal processing and habituation of responses to repeated sounds. Given the therapeutic potential of the antibiotic minocycline in humans with FXS and animal models, it is important to determine sensitivity and selectivity of EEG responses to minocycline. Therefore, in this study, we examined if a 10-day treatment of adult Fmr1 KO mice with minocycline (oral gavage, 30 mg/kg per day) would reduce EEG abnormalities. We tested if minocycline treatment has specific effects based on the EEG measurement type (e.g., resting versus sound-evoked) from the frontal and auditory cortex of the Fmr1 KO mice. We show increased resting EEG gamma power and reduced phase locking to time varying stimuli as well as the 40 Hz auditory steady state response in the Fmr1 KO mice in the pre-drug condition. Minocycline treatment increased gamma band phase locking in response to auditory stimuli, and reduced sound-evoked power of auditory event related potentials (ERP) in Fmr1 KO mice compared to vehicle treatment. Minocycline reduced resting EEG gamma power in Fmr1 KO mice, but this effect was similar to vehicle treatment. We also report frequency band-specific effects on EEG responses. Taken together, these data indicate that sound-evoked EEG responses may serve as more sensitive measures, compared to resting EEG measures, to isolate minocycline effects from placebo in humans with FXS. Given the use of minocycline and EEG recordings in a number of neurodegenerative and neurodevelopmental conditions, these findings may be more broadly applicable in translational neuroscience., (Copyright © 2020 Lovelace, Ethell, Binder and Razak.)

Objective: To determine the role of aquaporin-4 (AQP4) in posttraumatic epileptogenesis using long-term video-electroencephalographic (vEEG) recordings. Here, differences in EEG were analyzed between wild-type (WT) and AQP4 knockout (KO) mice and between mice with and without posttraumatic epilepsy (PTE)., Methods: WT and AQP4 KO mice were subjected to a single controlled cortical impact traumatic brain injury (TBI) in the frontal cortex, and vEEG was recorded in the ipsilateral hippocampus at 14, 30, 60, and 90 days postinjury (dpi). Intrahippocampal electrical stimulation was also used to assess electrographic seizure threshold and electrographic seizure duration (ESD)., Results: The mean seizure frequency per day for WT mice was 0.07 ± 0.07, 0.11 ± 0.07, 0.26 ± 0.13, and 0.12 ± 0.10 at 14, 30, 60, and 90 dpi, respectively. The mean seizure frequency per day for AQP4 KO mice was 0.45 ± 0.27, 0.29 ± 0.12, and 0.26 ± 0.19 at 14, 30, and 60 dpi, respectively. The mean seizure duration was 15 ± 2 seconds and 24 ± 3 seconds for WT and AQP4 KO mice, respectively. The percentage of mice that developed PTE were 28% and 37% for WT and AQP4 KO mice, respectively. Power spectral density (PSD) analysis revealed alterations in EEG frequency bands between sham and TBI in both genotypes. Additionally, PSD analysis of spontaneous recurrent seizures revealed alterations in delta power between genotypes. Morlet wavelet analysis detected heterogeneity in EEG seizure subtypes and dynamic EEG power patterns after TBI. Compared with AQP4 KO mice, a significant increase in ESD was observed in WT mice at 14 dpi., Significance: Posttraumatic seizures (PTSs) may be modulated by the astrocyte water channel AQP4. Absence of AQP4 increases the number of spontaneous seizures, increases seizure duration, and alters EEG power patterns of PTSs., (© 2020 International League Against Epilepsy.)

Repeated non-diffuse optical imaging of the brain is difficult. This is due to the fact that the cranial bone is highly scattering and thus a strong optical barrier. Repeated craniotomies increase the risk of complications and may disrupt the biological systems being imaged. We previously introduced a potential solution in the form of a transparent ceramic cranial implant called the Window to the Brain (WttB) implant. This implant is made of nanocrystalline Yttria-Stabilized Zirconia (nc-YSZ), which possesses the requisite mechanical strength to serve as a permanent optical access window in human patients. In this present study, we demonstrate repeated brain imaging of n = 5 mice using both OCT and LSI across the WttB implant over 4 weeks. The main objectives are to determine if the WttB implant allows for chronic OCT imaging, and to shed further light on the question of whether optical access provided by the WttB implant remains stable over this duration in the body. The Window to the Brain implant allowed for stable repeated imaging of the mouse brain with Optical Coherence Tomography over 28 days, without loss of signal intensity. Repeated Laser Speckle Imaging was also possible over this timeframe, but signal to noise ratio and the sharpness of vessels in the images decreased with time. This can be partially explained by elevated blood flow during the first imaging session in response to trauma from the surgery, which was also detected by OCT flow imaging. These results are promising for long-term optical access through the WttB implant, making feasible chronic in vivo studies in multiple neurological models of brain disease., (Copyright © 2020 Halaney, Jonak, Liu, Davoodzadeh, Cano-Velázquez, Ehtiyatkar, Park, Binder and Aguilar.)

Sensory processing abnormalities are frequently associated with autism spectrum disorders, but the underlying mechanisms are unclear. Here we studied auditory processing in a mouse model of Fragile X Syndrome (FXS), a leading known genetic cause of autism and intellectual disability. Both humans with FXS and the Fragile X mental retardation gene ( Fmr1 ) knockout (KO) mouse model show auditory hypersensitivity, with the latter showing a strong propensity for audiogenic seizures (AGS) early in development. Because midbrain abnormalities cause AGS, we investigated whether the inferior colliculus (IC) of the Fmr1 KO mice shows abnormal auditory processing compared with wild-type (WT) controls at specific developmental time points. Using antibodies against neural activity marker c-Fos, we found increased density of c-Fos+ neurons in the IC, but not auditory cortex, of Fmr1 KO mice at P21 and P34 following sound presentation. In vivo single-unit recordings showed that IC neurons of Fmr1 KO mice are hyperresponsive to tone bursts and amplitude-modulated tones during development and show broader frequency tuning curves. There were no differences in rate-level responses or phase locking to amplitude-modulated tones in IC neurons between genotypes. Taken together, these data provide evidence for the development of auditory hyperresponsiveness in the IC of Fmr1 KO mice. Although most human and mouse work in autism and sensory processing has centered on the forebrain, our new findings, along with recent work on the lower brainstem, suggest that abnormal subcortical responses may underlie auditory hypersensitivity in autism spectrum disorders. NEW & NOTEWORTHY Autism spectrum disorders (ASD) are commonly associated with sensory sensitivity issues, but the underlying mechanisms are unclear. This study presents novel evidence for neural correlates of auditory hypersensitivity in the developing inferior colliculus (IC) in Fmr1 knockout (KO) mouse, a mouse model of Fragile X Syndrome (FXS), a leading genetic cause of ASD. Responses begin to show genotype differences between postnatal days 14 and 21, suggesting an early developmental treatment window.

Fragile X Syndrome (FXS) is a leading known genetic cause of intellectual disability with symptoms that include increased anxiety and social and sensory processing deficits. Recent EEG studies in humans with FXS have identified neural oscillation deficits that include increased resting state gamma power, increased amplitude of auditory evoked potentials, and reduced inter-trial phase coherence of sound-evoked gamma oscillations. Identification of comparable EEG biomarkers in mouse models of FXS could facilitate the pre-clinical to clinical therapeutic pipeline. However, while human EEG studies have involved 128-channel scalp EEG acquisition, no mouse studies have been performed with more than three EEG channels. In the current study, we employed a recently developed 30-channel mouse multielectrode array (MEA) system to record and analyze resting and stimulus-evoked EEG signals in WT vs. Fmr1 KO mice. Using this system, we now report robust MEA-derived phenotypes including higher resting EEG power, altered event-related potentials (ERPs) and reduced inter-trial phase coherence to auditory chirp stimuli in Fmr1 KO mice that are remarkably similar to those reported in humans with FXS. We propose that the MEA system can be used for: (i) derivation of higher-level EEG parameters; (ii) EEG biomarkers for drug testing; and (ii) mechanistic studies of FXS pathophysiology., Competing Interests: Declaration of Competing Interest None., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

Fragile X syndrome (FXS) is a leading genetic cause of autism with symptoms that include sensory processing deficits. In both humans with FXS and a mouse model [Fmr1 knockout (KO) mouse], electroencephalographic (EEG) recordings show enhanced resting state gamma power and reduced sound-evoked gamma synchrony. We previously showed that elevated levels of matrix metalloproteinase-9 (MMP-9) may contribute to these phenotypes by affecting perineuronal nets (PNNs) around parvalbumin (PV) interneurons in the auditory cortex of Fmr1 KO mice. However, how different cell types within local cortical circuits contribute to these deficits is not known. Here, we examined whether Fmr1 deletion in forebrain excitatory neurons affects neural oscillations, MMP-9 activity, and PV/PNN expression in the auditory cortex. We found that cortical MMP-9 gelatinase activity, mTOR/Akt phosphorylation, and resting EEG gamma power were enhanced in CreNex1/Fmr1Flox/y conditional KO (cKO) mice, whereas the density of PV/PNN cells was reduced. The CreNex1/Fmr1Flox/y cKO mice also show increased locomotor activity, but not the anxiety-like behaviors. These results indicate that fragile X mental retardation protein changes in excitatory neurons in the cortex are sufficient to elicit cellular, electrophysiological, and behavioral phenotypes in Fmr1 KO mice. More broadly, these results indicate that local cortical circuit abnormalities contribute to sensory processing deficits in autism spectrum disorders., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Fragile X syndrome (FXS) is the most common genetic cause of autism and intellectual disability. Fragile X mental retardation gene (Fmr1) knock-out (KO) mice display core deficits of FXS, including abnormally increased sound-evoked responses, and show a delayed development of parvalbumin (PV) cells. Here, we present the surprising result that sound exposure during early development reduces correlates of auditory hypersensitivity in Fmr1 KO mice., Methods: Fmr1 KO and wild-type (WT) mice were raised in a sound-attenuated environment (AE) or sound-exposed (SE) to 14 kHz tones (5 Hz repetition rate) from P9 until P21. At P21-P23, event-related potentials (ERPs), dendritic spine density, PV expression and phosphorylation of tropomyosin receptor kinase B (TrkB) were analyzed in the auditory cortex of AE and SE mice., Results: Enhanced N1 amplitude of ERPs, impaired PV cell development, and increased spine density in layers (L) 2/3 and L5/6 excitatory neurons were observed in AE Fmr1 KO compared to WT mice. In contrast, developmental sound exposure normalized ERP N1 amplitude, density of PV cells and dendritic spines in SE Fmr1 KO mice. Finally, TrkB phosphorylation was reduced in AE Fmr1 KO, but was enhanced in SE Fmr1 KO mice, suggesting that BDNF-TrkB signaling may be regulated by sound exposure to influence PV cell development., Conclusions: Our results demonstrate that sound exposure, but not attenuation, during early developmental window restores molecular, cellular and functional properties in the auditory cortex of Fmr1 KO mice, and suggest this approach as a potential treatment for sensory phenotypes in FXS., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Posttraumatic epilepsy (PTE) is a long-term negative consequence of traumatic brain injury (TBI) in which recurrent spontaneous seizures occur after the initial head injury. PTE develops over an undefined period during which circuitry reorganization in the brain causes permanent hyperexcitability. The pathophysiology by which trauma leads to spontaneous seizures is unknown and clinically relevant models of PTE are key to understanding the molecular and cellular mechanisms underlying the development of PTE. In the present study, we used the controlled-cortical impact (CCI) injury model of TBI to induce PTE in mice and to characterize changes in aquaporin-4 (AQP4) expression. A moderate-severe TBI was induced in the right frontal cortex and video-electroencephalographic (vEEG) recordings were performed in the ipsilateral hippocampus to monitor for spontaneous seizures at 14, 30, 60, and 90 days post injury (dpi). The percentage of mice that developed PTE were 13%, 20%, 27%, and 14% at 14, 30, 60, and 90 dpi, respectively. We found a significant increase in AQP4 in the ipsilateral frontal cortex and hippocampus of mice that developed PTE compared to those that did not develop PTE. Interestingly, AQP4 was found to be mislocalized away from the perivascular endfeet and towards the neuropil in mice that developed PTE. Here, we report for the first time, AQP4 dysregulation in a model of PTE which may carry significant implications for epileptogenesis after TBI., (Copyright © 2019 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Astrocytes and neurons have been shown to swell across a variety of different conditions, including increases in extracellular potassium concentration (^[K + ] o ). The mechanisms involved in the coupling of K + influx to water movement into cells leading to cell swelling are not well understood and remain controversial. Here, we set out to determine the effects of ^[K + ] o on rapid volume responses of hippocampal CA1 pyramidal neurons and stratum radiatum astrocytes using real-time confocal volume imaging. First, we found that elevating [K + ] o within a physiological range (to 6.5 mM and 10.5 mM from a baseline of 2.5 mM), and even up to pathological levels (26 mM), produced dose-dependent increases in astrocyte volume, with absolutely no effect on neuronal volume. In the absence of compensating for addition of KCl by removal of an equal amount of NaCl, neurons actually shrank in ^[K + ] o , while astrocytes continued to exhibit rapid volume increases. Astrocyte swelling in ^[K + ] o was not dependent on neuronal firing, aquaporin 4, the inwardly rectifying potassium channel Kir 4.1, the sodium bicarbonate cotransporter NBCe1, , or the electroneutral cotransporter, sodium-potassium-chloride cotransporter type 1 (NKCC1), but was significantly attenuated in 1 mM barium chloride (BaCl 2 ) and by the Na + /K + ATPase inhibitor ouabain. Effects of 1 mM BaCl 2 and ouabain applied together were not additive and, together with reports that BaCl 2 can inhibit the NKA at high concentrations, suggests a prominent role for the astrocyte NKA in rapid astrocyte volume increases occurring in ^[K + ] o . These findings carry important implications for understanding mechanisms of cellular edema, regulation of the brain extracellular space, and brain tissue excitability.

Area II of the 2014 Epilepsy Research Benchmarks aims to establish goals for preventing the development and progression of epilepsy. In this review, we will highlight key advances in Area II since the last summary of research progress and opportunities was published in 2016. We also highlight areas of investigation that began to develop before 2016 and in which additional progress has been made more recently.

Background and Objective: Microcirculation plays a critical role in physiologic processes and several disease states. Laser speckle imaging (LSI) is a full-field, real-time imaging technique capable of mapping microvessel networks and providing relative flow velocity within the vessels. In this study, we demonstrate that LSI combine with multispectral reflectance imaging (MSRI), which allows for distinction between veins and arteries in the vascular flow maps produced by LSI. We apply this combined technique to mouse cerebral vascular network in vivo, comparing imaging through the skull, to the dura mater and brain directly through a craniectomy, and through a transparent cranial "Window to the Brain" (WttB) implant., Study Design/materials and Methods: The WttB implant used in this study is made of a nanocrystalline Yttria-Stabilized-Zirconia ceramic. MSRI was conducted using white-light illumination and filtering the reflected light for 560, 570, 580, 590, 600, and 610 nm. LSI was conducted using an 810 nm continuous wave near-infrared laser with incident power of 100 mW, and the reflected speckle pattern was captured by a complementary metal-oxide-semiconductor (CMOS) camera., Results: Seven vessel branches were analyzed and comparison was made between imaging through the skull, craniectomy, and WttB implant. Through the skull, MSRI did not detect any vessels, and LSI could not image microvessels. Imaging through the WttB implant, MSRI was able to identify veins versus arteries, and LSI was able to image microvessels with only slightly higher signal-to-noise ratio and lower sharpness than imaging the brain through a craniectomy., Conclusions: This study demonstrates the ability to perform MSRI-LSI across a transparent cranial implant, to allow for cerebral vascular networks to be mapped, including microvessels. These images contain additional information such as vein-artery separation and relative blood flow velocities, information which is of value scientifically and medically. The WttB implant provides substantial improvements over imaging through the murine cranial bone, where microvessels are not visible and MSRI cannot be performed. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc., (© 2019 Wiley Periodicals, Inc.)

Fragile X Syndrome (FXS) is a leading genetic cause of autism and intellectual disabilities. The Fmr1 knockout (KO) mouse is a commonly studied pre-clinical model of FXS. Adult male Fmr1 KO mice produce fewer ultrasonic vocalizations (USVs) during mating, suggestive of abnormal social communication. Minocycline treatment for 2 months from birth alleviates a number of FXS phenotypes in mice, including USV call rate deficits. In the current study, we investigated if treatment initiated past the early developmental period would be effective, given that in many cases, individuals with FXS are treated during later developmental periods. Wildtype (WT) and Fmr1 KO mice were treated with minocycline between postnatal day (P) 30 and P58. Mating-related USVs were then recorded from these mice between P75 and P90 and analyzed for call rate, duration, bandwidth, and peak frequency. Untreated Fmr1 KO mice call at a significantly reduced rate compared to untreated WT mice. After minocycline treatment from 1 to 2 months of age, WT and Fmr1 KO mice exhibited similar call rates, due to an increase in calling in the latter group. Minocycline is thought to be effective in reducing FXS symptoms by lowering matrix-metalloproteinase-9 (MMP-9) levels. To determine whether abnormal MMP-9 levels underlie USV deficits, we characterized USVs in Fmr1 KO mice which were heterozygous for MMP-9 (MMP-9 +/- /Fmr1 KO). The MMP-9 +/- /Fmr1 KO mice were between P75 and P90 at the time of recording. MMP-9 +/- /Fmr1 KO mice exhibited significantly increased USV call rates, at times even exceeding WT rates. Taken together, these results suggest that minocycline may reverse USV call rate deficits in Fmr1 KO mice through attenuation of MMP-9 levels. These data suggest targeting MMP-9, even in late development, may reduce FXS symptoms., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Fragile X Syndrome (FXS) is a leading cause of heritable intellectual disability and autism. Humans with FXS show anxiety, sensory hypersensitivity and impaired learning. The mechanisms of learning impairments can be studied in the mouse model of FXS, the Fmr1 KO mouse, using tone-associated fear memory paradigms. Our previous study reported impaired development of parvalbumin (PV) positive interneurons and perineuronal nets (PNN) in the auditory cortex of Fmr1 KO mice. A recent study suggested PNN dynamics in the auditory cortex following tone-shock association is necessary for fear expression. Together these data suggest that abnormal PNN regulation may underlie tone-fear association learning deficits in Fmr1 KO mice. We tested this hypothesis by quantifying PV and PNN expression in the amygdala, hippocampus and auditory cortex of Fmr1 KO mice following fear conditioning. We found impaired tone-associated memory formation in Fmr1 KO mice. This was paralleled by impaired learning-associated regulation of PNNs in the superficial layers of auditory cortex in Fmr1 KO mice. PV cell density decreased in the auditory cortex in response to fear conditioning in both WT and Fmr1 KO mice. Learning-induced increase of PV expression in the CA3 hippocampus was only observed in WT mice. We also found reduced PNN density in the amygdala and auditory cortex of Fmr1 KO mice in all conditions, as well as reduced PNN intensity in CA2 hippocampus. There was a positive correlation between tone-associated memory and PNN density in the amygdala and auditory cortex, consistent with a tone-association deficit. Altogether our studies suggest a link between impaired PV and PNN regulation within specific regions of the fear conditioning circuit and impaired tone memory formation in Fmr1 KO mice., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Sensory processing abnormalities are consistently associated with autism, but the underlying mechanisms and treatment options are unclear. Fragile X Syndrome (FXS) is the leading known genetic cause of intellectual disabilities and autism. One debilitating symptom of FXS is hypersensitivity to sensory stimuli. Sensory hypersensitivity is seen in both humans with FXS and FXS mouse model, the Fmr1 knock out (Fmr1 KO) mouse. Abnormal sensorimotor gating may play a role in the hypersensitivity to sensory stimuli. Humans with FXS and Fmr1 KO mice show abnormalities in acoustic startle response (ASR) and prepulse inhibition (PPI) of startle, responses commonly used to quantify sensorimotor gating. Recent studies have suggested high levels of matrix metalloproteinase-9 (MMP-9) as a potential mechanism of sensory abnormalities in FXS. Here we tested the hypothesis that genetic reduction of MMP-9 in Fmr1 KO mice rescues ASR and PPI phenotypes in adult Fmr1 KO mice. We measured MMP-9 levels in the inferior colliculus (IC), an integral region of the PPI circuit, of WT and Fmr1 KO mice at P7, P12, P18, and P40. MMP-9 levels were higher in the IC of Fmr1 KO mice during early development (P7, P12), but not in adults. We compared ASR and PPI responses in young (P23-25) and adult (P50-80) Fmr1 KO mice to their age-matched wildtype (WT) controls. We found that both ASR and PPI were reduced in the young Fmr1 KO mice compared to age-matched WT mice. There was no genotype difference for ASR in the adult mice, but PPI was significantly reduced in the adult Fmr1 KO mice. The adult mouse data are similar to those observed in humans with FXS. Genetic reduction of MMP-9 in the Fmr1 KO mice resulted in a rescue of adult PPI responses to WT levels. Taken together, these results show sensorimotor gating abnormalities in Fmr1 KO mice, and suggest the potential for MMP-9 regulation as a therapeutic target to reduce sensory hypersensitivity., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Astrocytes regulate extracellular glutamate homeostasis in the central nervous system through the Na + -dependent glutamate transporters glutamate transporter-1 (GLT-1) and glutamate aspartate transporter (GLAST). Impaired astrocyte glutamate uptake could contribute to the development of epilepsy but the regulation of glutamate transporters in epilepsy is not well understood. In this study, we investigate the expression of GLT-1 and GLAST in the mouse intrahippocampal kainic acid (IHKA) model of temporal lobe epilepsy (TLE). We used immunohistochemistry, synaptosomal fractionation and Western blot analysis at 1, 3, 7 and 30 days post-IHKA induced status epilepticus (SE) to examine changes in GLT-1 and GLAST immunoreactivity and synaptosomal expression during the development of epilepsy. We found a significant upregulation in GLT-1 immunoreactivity at 1 and 3 days post-IHKA in the ipsilateral dorsal hippocampus. However, GLT-1 immunoreactivity and synaptosomal protein levels were significantly downregulated at 7 days post-IHKA in the ipsilateral hippocampus, a time point corresponding to the onset of spontaneous seizures in this model. GLAST immunoreactivity was increased in specific layers at 1 and 3 days post-IHKA in the ipsilateral hippocampus. GLAST synaptosomal protein levels were significantly elevated at 30 days compared to 7 days post-IHKA in the ipsilateral hippocampus. Our findings suggest that astrocytic glutamate transporter dysregulation could contribute to the development of epilepsy., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Glutamate transporter-1 (GLT-1) is a Na + -dependent transporter that plays a key role in glutamate homeostasis by removing excess glutamate in the central nervous system (CNS). GLT-1 dysregulation occurs in various neurological diseases including Huntington's disease (HD), Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and epilepsy. Downregulation or dysfunction of GLT-1 has been a common finding across these diseases but how this occurs is still under investigation. This review aims to highlight post-translational regulation of GLT-1 which leads to its downregulation including sumoylation, palmitoylation, nitrosylation, ubiquitination, and subcellular localization. Various therapeutic interventions to restore GLT-1, their proposed mechanism of action and functional effects will be examined as potential treatments to attenuate the neurological symptoms associated with loss or downregulation of GLT-1.

We report on the enhanced optical transmittance in the NIR wavelength range (900 to 2400 nm) offered by a transparent Yttria-stabilized zirconia (YSZ) implant coupled with optical clearing agents (OCAs). The enhancement in optical access to the brain is evaluated upon comparing ex-vivo transmittance measurements of mice native skull and the YSZ cranial implant with scalp and OCAs. An increase in transmittance of up to 50% and attenuation lengths of up to 2.4 mm (i.e., a five-fold increase in light penetration) are obtained with the YSZ implant and the OCAs. The use of this ceramic implant and the biocompatible optical clearing agents offer attractive features for NIR optical techniques for brain theranostics., Competing Interests: The authors declare that there are no conflicts of interest related to this article.

Fragile X Syndrome (FXS) is a leading genetic cause of autism and intellectual disabilities. Sensory-processing deficits are common in humans with FXS and an animal model, the Fmr1 knockout (KO) mouse, manifesting in the auditory system as debilitating hypersensitivity and abnormal electroencephalographic (EEG) and event-related potential (ERP) phenotypes. FXS is a neurodevelopmental disorder, but how EEG/ERP phenotypes change during development is unclear. Therefore, we characterized baseline and stimulus-evoked EEG in auditory and frontal cortex of developing (postnatal day (P) 21 and P30) and adult (P60) wildtype (WT) and Fmr1 KO mice with the FVB genetic background. We found that baseline gamma-band power and N1 amplitude of auditory ERP were increased in frontal cortex of Fmr1 KO mice during development and in adults. Baseline gamma power was increased in auditory cortex at P30. Genotype differences in stimulus-evoked gamma power were present in both cortical regions, but the direction and strength of the changes were age-dependent. These findings suggest that cortical deficits are present during early development and may contribute to sensory-processing deficits in FXS, which in turn may lead to anxiety and delayed language. Developmental changes in EEG measures indicate that observations at a single time-point during development are not reflective of FXS disease progression and highlight the need to identify developmental trajectories and optimal windows for treatment., (Copyright © 2018 IBRO. Published by Elsevier Ltd. All rights reserved.)

Abnormal sensory responses associated with Fragile X Syndrome (FXS) and autism spectrum disorders include hypersensitivity and impaired habituation to repeated stimuli. Similar sensory deficits are also observed in adult Fmr1 knock-out (KO) mice and are reversed by genetic deletion of Matrix Metalloproteinase-9 (MMP-9) through yet unknown mechanisms. Here we present new evidence that impaired development of parvalbumin (PV)-expressing inhibitory interneurons may underlie hyper-responsiveness in auditory cortex of Fmr1 KO mice via MMP-9-dependent regulation of perineuronal nets (PNNs). First, we found that PV cell development and PNN formation around GABAergic interneurons were impaired in developing auditory cortex of Fmr1 KO mice. Second, MMP-9 levels were elevated in P12-P18 auditory cortex of Fmr1 KO mice and genetic reduction of MMP-9 to WT levels restored the formation of PNNs around PV cells. Third, in vivo single-unit recordings from auditory cortex neurons showed enhanced spontaneous and sound-driven responses in developing Fmr1 KO mice, which were normalized following genetic reduction of MMP-9. These findings indicate that elevated MMP-9 levels contribute to the development of sensory hypersensitivity by influencing formation of PNNs around PV interneurons suggesting MMP-9 as a new therapeutic target to reduce sensory deficits in FXS and potentially other autism spectrum disorders.

Translational comparison of rodent models of neurological and neuropsychiatric diseases to human electroencephalography (EEG) biomarkers in these conditions will require multisite rodent EEG on the skull surface, rather than local area electrocorticography (ECoG) or multisite local field potential (LFP) recording. We have developed a technique for planar multielectrode array (MEA) implantation on the mouse skull surface, which enables multisite EEG in awake and freely moving mice and reusability of the MEA probes. With this method, we reliably obtain 30-channel low-noise EEG from awake mice. Baseline and stimulus-evoked EEG recordings can be readily obtained and analyzed. For example, we have demonstrated EEG responses to auditory stimuli. Broadband noise elicits reliable 30-channel auditory event-related potentials (ERPs), and chirp stimuli induce phase-locked EEG responses just as in human sound presentation paradigms. This method is unique in achieving chronic implantation of novel MEA technology onto the mouse skull surface for chronic multisite EEG recordings. Furthermore, we demonstrate a reliable method for reusing MEA probes for multiple serial implantations without loss of EEG quality. This skull surface MEA methodology can be used to obtain simultaneous multisite EEG recordings and to test EEG biomarkers in diverse mouse models of human neurological and neuropsychiatric diseases. Reusability of the MEA probes makes it more cost-effective to deploy this system for various studies.

Laser speckle imaging (LSI) of mouse cerebral blood flow was compared through a transparent nanocrystalline yttria-stabilized zirconia (nc-YSZ) cranial implant over time (at days 0, 14, and 28, n = 3 mice), and vs. LSI through native skull (at day 60, n = 1 mouse). The average sharpness of imaged vessels was found to remain stable, with relative change in sharpness under 7.69% ± 1.2% over 28 days. Through-implant images of vessels at day 60 appeared sharper and smaller on average, with microvessels clearly visible, compared to through-skull images where vessels appeared blurred and distorted. These results suggest that long-term imaging through this implant is feasible., Competing Interests: The authors declare that there are no conflicts of interest related to this article.

Perineuronal nets (PNN) are extracellular matrix (ECM) assemblies that preferentially ensheath parvalbumin (PV) expressing interneurons. Converging evidence indicates that PV cells and PNN are impaired in a variety of neurological disorders. PNN development and maintenance is necessary for a number of processes within the CNS, including regulation of GABAergic cell function, protection of neurons from oxidative stress, and closure of developmental critical period plasticity windows. Understanding PNN functions may be essential for characterizing the mechanisms of altered cortical excitability observed in neurodegenerative and neurodevelopmental disorders. Indeed, PNN abnormalities have been observed in post-mortem brain tissues of patients with schizophrenia and Alzheimer's disease. There is impaired development of PNNs and enhanced activity of its key regulator matrix metalloproteinase-9 (MMP-9) in Fragile X Syndrome, a common genetic cause of autism. MMP-9, a protease that cleaves ECM, is differentially regulated in a number of these disorders. Despite this, few studies have addressed the interactions between PNN expression, MMP-9 activity and neuronal excitability. In this review, we highlight the current evidence for PNN abnormalities in CNS disorders associated with altered network function and MMP-9 levels, emphasizing the need for future work targeting PNNs in pathophysiology and therapeutic treatment of neurological disorders.

Identification of comparable biomarkers in humans and validated animal models will facilitate pre-clinical to clinical therapeutic pipelines to treat neurodevelopmental disorders. Fragile X Syndrome (FXS) is a leading known genetic cause of intellectual disability with symptoms that include increased anxiety, social and sensory processing deficits. Recent EEG studies in humans with FXS have identified neural oscillation deficits that include enhanced resting state gamma power and reduced inter-trial coherence of sound evoked gamma oscillations. To determine if analogous phenotypes are present in an animal model of FXS, we recorded EEGs in awake, freely moving Fmr1 knock out (KO) mice using similar stimuli as in the human studies. We report remarkably similar neural oscillation phenotypes in the Fmr1 KO mouse including enhanced resting state gamma power and reduced evoked gamma synchronization. The gamma band inter-trial coherence of neural response was reduced in both auditory and frontal cortex of Fmr1 KO mice stimulated with a sound whose envelope was modulated from 1 to 100 Hz, similar to that seen in humans with FXS. These deficits suggest a form of enhanced 'resting state noise' that interferes with the ability of the circuit to mount a synchronized response to sensory input, predicting specific sensory and cognitive deficits in FXS. The abnormal gamma oscillations are consistent with parvalbumin neuron and perineuronal net deficits seen in the Fmr1 KO mouse auditory cortex indicating that the EEG biomarkers are not only clinically relevant, but could also be used to probe cellular and circuit mechanisms of sensory hypersensitivity in FXS., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Fragile X syndrome (FXS) is a neurodevelopmental disorder that causes intellectual disability. It is a leading known genetic cause of autism. In addition to cognitive, social, and communication deficits, humans with FXS demonstrate abnormal sensory processing including sensory hypersensitivity. Sensory hypersensitivity commonly manifests as auditory, tactile, or visual defensiveness or avoidance. Clinical, behavioral, and electrophysiological studies consistently show auditory hypersensitivity, impaired habituation to repeated sounds, and reduced auditory attention in humans with FXS. Children with FXS also exhibit significant visuospatial impairments. Studies in infants and toddlers with FXS have documented impairments in processing texture-defined motion stimuli, temporal flicker, perceiving ordinal numerical sequence, and the ability to maintain the identity of dynamic object information during occlusion. Consistent with the observations in humans with FXS, fragile X mental retardation 1 ( Fmr1) gene knockout (KO) rodent models of FXS also show seizures, abnormal visual-evoked responses, auditory hypersensitivity, and abnormal processing at multiple levels of the auditory system, including altered acoustic startle responses. Among other sensory symptoms, individuals with FXS exhibit tactile defensiveness. Fmr1 KO mice also show impaired encoding of tactile stimulation frequency and larger size of receptive fields in the somatosensory cortex. Since sensory deficits are relatively more tractable from circuit mechanisms and developmental perspectives than more complex social behaviors, the focus of this review is on clinical, functional, and structural studies that outline the auditory, visual, and somatosensory processing deficits in FXS. The similarities in sensory phenotypes between humans with FXS and animal models suggest a likely conservation of basic sensory processing circuits across species and may provide a translational platform to not just develop biomarkers but also to understand underlying mechanisms. We argue that preclinical studies in animal models of FXS can facilitate the ongoing search for new therapeutic approaches in FXS by understanding mechanisms of basic sensory processing circuits and behaviors that are conserved across species.