Role of depolarizing GABAergic transmission for cortical network development

GABA mediates synaptic inhibition in the adult brain. However, in early development elevated intracellular Cl concentration ([Cl]in) by NKCC1 causes GABAA receptor (GABAAR) activation to be depolarizing in immature cortical neurons. Despite the potential promotion effect of depolarizing GABA for neuronal network development, a coherent picture cannot be drawn due to a lack of appropriate tools to manipulate the [Cl]in in the central nervous system (CNS). An Emx1-dependent conditional NKCC1 knockout mouse line which harbors disrupted NKCC1 function in cortical pyramidal cells and glia cells but leaving interneurons unaffected was used to explore the role of depolarizing GABAergic transmission on cortical network development. Optimized photo-stimulation of the optogenetic Cl pump eNpHR3.0 enables stable photo-currents, hence Cl loading, on longer time-scales. Next, combined with the optogenetic tool and patch-clamp techniques, the present work shows that NKCC1 contributes to GABAergic depolarization, and eNpHR3.0-mediated artificial loading of Cl in Emx1 positive cells contributes to the generation of spontaneous correlated network activity in the hippocampus in vitro. Disruption of NKCC1 function in Emx1 positive cells impairs such activity. However, this impairment is not due to an altered intrinsic excitability. In addition, the synaptic maturation is not affected in both GABAergic and glutamatergic synaptic transmission. The GABAAR-mediated mGPSCs in cells from NKCC1 KOEmx1 animals undergo a normal developmental increase in frequency and acceleration in decay kinetics, while the AMPAR-mediated mEPSCs undergo a developmental increase in frequency and slowdown in decay kinetics. Three-dimensional voxel-based two-photon imaging revealed column-like Ca2+ clusters in visual cortex representing early spontaneous network activity. With the use of in vivo wide-field imaging technique, the present work shows that the deletion of NKCC1 in Emx1 positive cells does not affect the development of spontaneous network activity in the visual cortex, as the Ca2+ cluster frequency and cluster size undergo a developmental increase and they do not significantly differ between WT and NKCC1 KOEmx1 animals. In conclusion, NKCC1-mediated depolarizing action of GABA is not required for major aspects of cortical network development although it contributes to the generation of spontaneous network activity in the hippocampus in vitro.GABA vermittelt synaptische Hemmung von Neuronen im adulten Gehirn. In der frühen Entwicklung bewirkt eine erhöhte intrazelluläre Cl– Konzentration ([Cl–]in) durch NKCC1, dass die Aktivierung des GABAA Rezeptors (GABAAR) in unreifen kortikalen Neuronen depolarisierend wirkt. Obwohl der depolarisierende Effekt von GABA möglicherweise zur Reifung neuronaler Netzwerke beiträgt, ergibt sich aktuell kein kohärentes Bild. Hierfür fehlten bislang geeignete Instrumente zur Manipulation von [Cl–]in im zentralen Nervensystem (ZNS). Eine Mauslinie mit einem konditionalen Knockout von NKCC1 unter der Kontrolle des Emx1 Promoters, die eine gestörte NKCC1 Funktion in kortikalen Pyramidenzellen und Gliazellen zur Folge hat, aber Interneurone unberührt lässt, wurde verwendet, um die Rolle der depolarisierenden GABAergen Übertragung für die Entwicklung des kortikalen Netzwerks zu untersuchen. Eine optimierte Photostimulation der optogenetischen Cl– Pumpe eNpHR3.0 ermöglicht stabile Photoströme und damit Cl– Beladung auf längeren Zeitskalen. Des Weiteren wird in der vorliegende Arbeit mithilfe optogenetischer Methoden und Patch-Clamp-Techniken nachgewiesen, dass NKCC1 zur GABAergen Depolarisation beiträgt und eine künstliche Beladung von Cl– durch eNpHR3.0 in Emx1 positiven Zellen das Auftreten spontaner korrelierter Netzwerkaktivität im Hippocampus begünstigt. Die genetische Deletion von NKCC1 in Emx1 positiven Zellen beeinträchtigt diese Aktivität. Die Beeinträchtigung kann jedoch nicht auf eine veränderte intrinsische Erregbarkeit zurückgeführt werden. Darüber hinaus ist die synaptische Reifung sowohl für GABAerge als auch für glutamaterge Übertragung nicht betroffen. Die GABAAR vermittelten mGPSCs in Zellen von NKCC1 KOEmx1 Tieren durchlaufen einen normalen Entwicklungsanstieg der Frequenz und eine Beschleunigung der Abklingkinetik, während die AMPAR vermittelten mEPSCs einen Entwicklungsanstieg der Frequenz und eine Verlangsamung der Abklingkinetik erfahren. Die dreidimensionale voxel-basierte Zwei-Photonen-Bildgebung zeigte säulenartige Ca2+ Cluster, welche die frühe spontane Netzwerkaktivität im visuellen Kortex repräsentieren. Mittels In-vivo-Weitfeld-Bildgebung konnte in der vorliegenden Arbeit gezeigt werden, dass die Deletion von NKCC1 in Emx1-positiven Zellen die Entwicklung spontaner Netzwerkaktivität im visuellen Kortex nicht beeinflusst, da die Ca2+ Clusterfrequenz und Clustergröße einen Entwicklungsanstieg erfahren und sich nicht zwischen WT und NKCC1 KOEmx1 Tieren signifikant unterscheiden. Zusammenfassend ist festzuhalten, dass die NKCC1-vermittelte depolarisierende Wirkung von GABA für wesentliche Aspekte der kortikalen Netzwerkentwicklung nicht erforderlich ist, obwohl sie in vitro zur Erzeugung der spontanen Netzwerkaktivität im Hippocampus beiträgt

Contribution of somatostatin interneurons to correlated neuronal activity in the developing hippocampus

Frühe korrelierte neuronale Aktivität tritt in Form synchroner Bursts von Aktionspotentialen in großen Zellpopulationen und in allen Teilen des sich entwickelnden Gehirns auf. Eine wachsende Zahl an Studien legt nahe, dass synchrone Aktivität einen wichtigen Beitrag zur Reifung des neuronalen Netzwerks leistet und dabei auftretende Störungen zur Fehlentwicklung des Nervensystems führen. Aus diesem Grund ist ein mechanistisches Verständnis der Generierung korrelierter neuronaler Aktivität von großer Bedeutung für die klinische Forschung. Im unreifen Hippokampus tritt synchrone Aktivität kurz nach der Geburt auf und ist hochgradig von der depolarisierenden Wirkung bei synaptischer GABAA-Rezeptor-Aktivierung abhängig. Interneurone, die GABA freisetzen, sind mit hoher Wahrscheinlichkeit an der Burst-Generierung beteiligt. Welche der anatomisch hochgradig heterogenen Subtypen GABAerger Interneurone an der Generierung korrelierter Aktivität im unreifen Hirn beteiligt sind, ist bislang nur unvollständig aufgeklärt. In der vorliegenden Dissertation wird der Beitrag der Somatostatinexprimierenden (SOM)-Interneurone an korrelierter neuronaler Aktivität im sich entwickelnden Hippokampus untersucht. Um die zugrundeliegenden synaptischen Mechanismen zu analysieren, kamen elektrophysiologische und optische Techniken an akuten hippokampalen Hirnschnitten von neonatalen Mäusen zum Einsatz. In einem transgenen Tiermodell wurde die Beteiligung von entweder glutamatergen Pyramidenzellen oder GABAergen SOM-Interneuronen an synchroner Aktivität mithilfe zellspezifischer Expression des Kalziumfarbstoffs GCaMP6s und schneller konfokaler Kalziumbildgebung sowie paralleler Ableitung des lokalen Feldpotentials untersucht. Es wurde gezeigt, dass beide Populationen während neuronaler Bursts spontan und hochgradig korreliert aktiv sind. Mittels der Expression des optisch-aktivierbaren Natriumkanals Channelrhodopsin 2 (ChR2) in SOM-Interneuronen (SOMChR2) wurden Aktionsströme optogenetisch induziert. Elektrophysiologische Messungen zeigten, dass die Photoaktivierung von SOM-Interneuronen eine GABAA-Rezeptor-abhängige synaptische Erregung von Pyramidenzellen zur Folge hat, die vom Chlorid-Importer NKCC1 abhängig ist. In Ableitungen von Pyramidenzellen mithilfe von Kalziumbildgebung wurde zudem gezeigt, dass die Photoaktivierung von SOMChR2 korrelierte Netzwerkaktivität ähnlich der Spontanaktivität induziert. Komplementär Zusammenfassung 4 wurde unter Verwendung einer optogenetischen Strategie zur Hemmung von SOMInterneuronen der Beitrag der spontanen Feuerrate dieser Nervenzellpopulation zur Burst-Generierung untersucht. Zu diesem Zweck wurden transgene Mäuse eingesetzt, welche die lichtgetriebene Chlorid-Pumpe eNpHR3.0 (HR3), ein molekulargenetisch optimiertes Halorhodopsin-Konstrukt, in SOM-Interneuronen (SOMHR3) exprimieren. Die Photoinhibition von SOMHR3 wurde für langanhaltende Hyperpolarisation der Zellen optimiert und reduzierte effektiv die spontane Feuerrate der SOM-Interneurone. Elektrophysiologische Messungen von Pyramidenzellen ergaben, dass die Photoinhibition von SOMHR3 eine Reduktion der Burst-Aktivität im Pyramidenzellband der CA1 Region des neonatalen Hippokampus zur Folge hat. Zusammenfassend zeigt die vorliegende Arbeit, dass SOM-Interneurone durch präsynaptisches spontanes Feuern von Aktionspotentialen und eine erregende postsynaptische GABAA-Rezeptor Aktivierung in glutamatergen Pyramidenzellen die korrelierte Netzwerkaktivität im sich entwickelnden Hippokampus antreiben. Die hier gefundenen Ergebnisse leisten einen wichtigen Beitrag zum mechanistischen Verständnis spontaner korrelierter Aktivität und der aktivitätsabhängigen Hirnreifung.Spontaneous correlated neuronal activity fine-tunes the developing brain and disturbances thereof may cause severe neurodevelopmental disorders. Hence, understanding the underlying mechanisms of early neuronal activity instructing the neuronal circuitry is a key for research of diseases and clinical prevention. In the immature hippocampus correlated bursts of neuronal activity occur at early perinatal stages and are highly dependent on a depolarizing postsynaptic current upon γ-amino-butyric-acid (GABA) gated ionotropic receptor (GABAAR) activation. The contribution of GABA-releasing interneuronal subpopulations to the mechanism of burst generation remains elusive. In the present work, the GABAergic subpopulation of somatostatin-expressing (SOM) interneurons and its role in spontaneous correlated neuronal activity is investigated in the developing hippocampus. To dissect the underlying synaptic mechanisms, electrophysiological and optical techniques were applied in acute hippocampal brain slices from neonatal mice. In a transgenic approach the participation of either glutamatergic pyramidal cells or GABAergic SOM interneurons during bursts were elucidated by the expression of the genetic Ca2+ indicator GCaMP6s and fast confocal Ca2+ imaging with parallel local field potential recordings. It was shown that both populations are during burst activity in a highly correlated manner. A light-gated Na+ channel, channelrhodopsin 2 (ChR2), was utilized in a SOM interneuron specific transgenic mouse model (SOMChR2) to evoke photo-activated action potential firing in this population. Electrophysiological measurements revealed a GABAAR-dependent synaptic connectivity with glutamatergic pyramidal cells in the CA1 pyramidal cell layer and an excitatory depolarizing mode of action at the postsynapses dependent on Cl–importer NKCC1. Furthermore, Ca2+ imaging from the pyramidal cell layer revealed that photo-activation of SOMChR2 evokes correlated neuronal activity reminiscent of spontaneous bursts. To elucidate the contribution of spontaneous action potential firing in SOM interneurons to burst generation, the light-activated chloride pump halorhodopsin (eNpHR3) was expressed under control of the SOM promoter (SOMHR3) in transgenic mice. Photo-stimulation of SOMHR3 was optimized for stable hyperpolarizing currents and effectively inhibited spontaneous action potential firing in SOM interneurons. Electrophysiological recordings from pyramidal cells revealed that photo-inhibition of SOM interneurons reduced burst activity in CA1 pyramidal cells. The mechanism of burst population dynamics was interpreted by a recurrent neural network model. Modeling the experimental findings revealed that tonic or temporally patterned GABA release from SOM interneurons elevates the activity level of the network due to the excitatory action of GABA towards a threshold and thereby either increases the probability of burst generation or simply triggers burst activity. In conclusion, the present work shows that SOM interneurons drive correlated activity in the developing hippocampus depending on spontaneous action potential firing of presynaptic SOM interneurons and depolarizing postsynaptic GABAAR activation in glutamatergic pyramidal cells. The results provided here causal understanding of correlated neuronal activity with important implications for activity-dependent brain maturation

In vivo imaging of the early embryonic cortex in rodents

Embryonic brain development is a highly dynamic period in human life. Any disturbances at this stage can cause life-long negative consequences, such as developmentally related diseases, including autism, schizophrenia, and bipolar spectrum disorders. During development the mother-embryo interface plays a crucial role in supplementing the growing organism with oxygen and nutrients, regulating chemical cues, and protecting it from infections and potentially hazardous compounds. However, most of the studies of embryonic brain development have utilized ex vivo systems such as slices and neuronal cultures. Despite the great value of the data obtained from ex vivo studies, they usually completely ignore the significance of the mother-embryo interaction. Thus, there is desperate need for novel preclinical models of embryonic development. In this thesis, we developed a novel technique for in vivo two-photon imaging in mouse embryos connected to the mother via umbilical cord. We developed the special chamber with polymer membrane allowing to keep embryos separately in the heated physiological solution while the umbilical connection to the anesthetized mother is preserved. We developed the protocol for stimulation of calcium activity using high-power laser radiation and studied the propagation of the resulting calcium waves in the mouse embryonic cortex in vivo under ketamine/xylazine anesthesia. We confirm the enhancing effect of caffeine on the evoked activity and the suppressing effect of the adenosine triphosphate (ATP) -receptor blockade, known from previous ex vivo studies. We analyzed the patterns of wave propagation and show the non-uniform spreading, which suggests the presence of differing connectivity patterns in the cortex already during the early stage of development. Further, we studied spontaneous calcium activity and cellular motility in the mouse embryonic cortex in vivo under light isoflurane anesthesia. We demonstrate two various patterns of ongoing activity: sporadic activation of single cells and correlated activity in the form of calcium waves. We show that blockade of N-methyl-D-aspartate (NMDA) receptors with ketamine inhibits the calcium activity in vivo, corresponding with the arrest of cellular motility. In the last part of the thesis, we studied the dynamics of the externally introduced substance to the mouse embryonic brains in vivo. We used porous silicon nanoparticles, which are a promising drug delivery platform, as they can be loaded with poorly water-soluble drugs. We show that the nanoparticles can breach the placental barrier and accumulate in the brains of the embryo. To study the dynamics of nanoparticles when already in the cortex, we injected the embryonic brains intraventricularly. Nanoparticles, including ones 3-4 um in size, were distributed in 80% of the cortex already 4 hours following the injection, thus demonstrating high motility in the brain tissue of embryos. We confirmed the motility of nanoparticles in real time using the in vivo two-photon imaging of embryos connected to the mother under ketamine/xylazine anesthesia. The results emphasize the susceptibility of the embryonic cortex at the early stage of development to external particles, which should be taken into account in nanomedicine development. In summary, the developed in vivo imaging technique allowed functional studies in the embryonic cortex in real time. This will allow preclinical pharmacological investigations of the compounds while maintaining the physiological mother-embryo interface.Sikiöiden aivojen kehittyminen on erittäin dynaaminen vaihe ihmiselämässä. Mikä tahansa häiriö tässä vaiheessa voi aiheuttaa elinikäisiä negatiivisia seurauksia, kuten kehitykseen liittyviä sairauksia, sisältäen autismin, skitsofrenian ja bipolaarihäiriöt. Kehityksen aikana äidin ja sikiön välisellä liitynnällä on kriittinen rooli hapen ja ravintoaineiden välittämisessä kasvavalle organismille, kemikaalien säännöstelyssä ja infektioilta ja mahdollisesti haitallisilta aineilta suojaamisessa. Kuitenkin suurin osa sikiön aivojen kehityksen tutkimuksista ovat hyödyntäneet ex vivo systeemejä, kuten leikkeitä ja neuronien kulttureita. Huolimatta ex vivo tutkimuksella kerätyn datan suuresta arvosta ne yleensä jättävät kokonaan huomiotta äidin ja sikiön välisen vuorovaikutuksen merkityksen. Täten uusille prekliinisille sikiön kehityksen malleille on välttämätön tarve. Tässä väitöskirjassa kehitettimme uusi tekniikka in vivo tuplafotonikuvantamiselle hiirisikiöissä, jotka ovat yhteydessä äitiin napanuoran kautta. Kehitimme erityisen polymeerikalvokammion, joka mahdollistaa sikiöiden pitämisen erillään lämmitetyssä fysiologisessa solutionissa sillä välin kun napanuorayhteys nukutettuun äitiin säilyyn. Kehitimme protokollan kalsiumaktiviteetin stimuloimiseen käyttäen suurteholaserin säteilyä ja tutkimme syntyvien kalsiumaaltojen etenemistä hiiren aivokuoressa in vivo ketamiini/xylasiini anestesiassa. Me vahvistamme kofeiinin edistävän vaikutuksen synnytettyyn aktiviteettiin, ja adenosiini trifosfaatti (ATP) reseptorin sulun heikentävän vaikutuksen, mitkä ovat tunnettuja aiemmista ex vivo tutkimuksista. Analysoimme aallon etenemistapoja ja näytämme epäyhtenäisen leviämisen, mikä viittaa siihen, että aivokuoressa on erilaistuneet yhteydet jo kehityksen aikaisessa vaiheessa. Lisäksi tutkimme spontaania kalsiumaktiviteettia ja solujen liikettä hiirisikiön aivokuoressa in vivo kevyen isofluraani anestesian alaisuudessa. Näytämme kaksi erilaista kaavaa olemassa olevassa aktiviteetissa: yksittäisten solujen saatunnainen aktiviteetti ja kalsiumaaltojen muodossa oleva korreloitunut aktiviteetti. Me näytämme, että N-metyyli-D-aspartaatin (NMDA) estoreseptorit yhdessä ketamiinin kanssa estää kalsiumaktiviteetin in vivo, mikä vastaa estoa soluliikkuvuudessa. Väitöskirjan viimeisessä osassa tutkimme ulkoisesti tuodun aineen dynamiikka hiirisikiöiden aivoissa in vivo. Käytimme huokoista silikonia, joka on lupaava lääkettä luovuttava alusta, sillä niihin voi kuormata lääkeitä, jotka liukenevat huonosti veteen. Näytämme että nanopartikkelit voivat mennä istukkaesteen läpi ja kerääntyä sikiöiden aivoihin. Tutkiaksemme nanopartikkelien dynamiikkaa aivokuoressa, me injektoimme sikiöiden aivoja intraventrikulaarisesti. Nanopartikkelit,sisältäen 3-4 um kokoisia partikkeleita, olivat hajautuneet 80 prosenttiin aivokuoresta jo neljä tuntia injektoinnn jälken, mikä demonstroi korkeaa nanopartikkeleiden liikkuvuutta sikiöiden aivoissa. Vahvistimme nanopartikkeleiden liikkuvuuden reaaliajassa in vivo tupla-fotonikuvantamisella sikiöillä, jotka ovat yhdistetty äiteihin ketamiini/ksylatsiini anestesiassa. Tulokset korostavat sikiön aivokuoren alttiutta ulkoisille hiukkasille, mikä tulisi ottaa huomioon nanolääkkeitä kehitettäessä. Yhteenvetona, kehitetty in vivo kuvaantamisen malli sallii toiminnallisten tutkimusten teon sikiöiden aivokuoressa reaaliajassa. Tämä mahdollistaa yhdisteiden prekliinisen farmakologisen tutkimisen samalla kun fysiologinen äiti-sikiö yhtymäkohta säilyy

Probing circuits for spinal motor control

Spinal circuits can generate locomotor output in the absence of sensory or descending input, but the principles of locomotor circuit organization remain unclear. We sought insight into these principles by considering the elaboration of locomotor circuits across evolution. The identity of limb-innervating motor neurons was reverted to a state resembling that of motor neurons that direct undulatory swimming in primitive aquatic vertebrates, permitting assessment of the role of motor neuron identity in determining locomotor pattern. Two-photon imaging was coupled with spike inference to measure locomotor firing in hundreds of motor neurons in isolated mouse spinal cords. In wild type preparations we observed sequential recruitment of motor neurons innervating flexor muscles controlling progressively more distal joints. Strikingly, after reversion of motor neuron identity virtually all firing patterns became distinctly flexor-like. Our interneuron imaging experiments demonstrate a new approach for functionally mapping the types of inputs that motor neurons might receive during locomotor firing. These data revealed that En1-derived inhibitory spinal interneuron activity appears to be dominated by a flexor-like pattern across the ventrolateral extent of the lumbar spinal cord–even in the regions surrounding flexor and extensor motor pools. Together, these findings show that motor neuron identity directs locomotor circuit wiring, and indicate the evolutionary primacy of flexor pattern generation

In vivo measurement of excitatory synaptic transmission between identified neurons in layer 2/3 mouse barrel cortex

The neocortex is the most distinctive feature of the mammalian brain and it is considered to be the substrate of high-order cognitive functions. The nature and the arrangement of the diverse neuronal elements constituting its multiple areas have received longstanding attention. Progressively such anatomical and functional investigations are undertaken in the context of an intact living being. It offers the possibility of examining the role of particular areas, networks or even individual neurons during various behavioral states. Synaptic connectivity and synaptic transmission have been traditionally investigated in reduced preparations. Typically, electrophysiological and optical techniques have been used to control and record the propagation of electrical activity between two or more neurons in acute brain slices in vitro. The purpose of this thesis is the investigation of synaptic connectivity and synaptic transmission within the intact neocortex of the living mouse. Here I took advantage of the recent development of optogenetics, in combination with electrophysiology and two-photon microscopy to systematically and directly record synaptic transmission between a single excitatory neuron and two main types of GABAergic neurons in layer 2/3 of the mouse barrel cortex in vivo. Overall, I discovered stronger excitatory connections onto GABAergic neurons than onto excitatory neurons, irrespective of the absolute or relative locations of the pre- and postsynaptic neurons somas. I further revealed that parvalbumin-expressing (PV) and somatostatin-expressing (Sst) GABAergic neurons received excitatory inputs that were similar in magnitude, but were more reliable and faster in PV neurons than in Sst neurons. Exploring postsynaptic responses to multiple presynaptic action potentials elicited at high frequency, I found a strong short-term facilitation accompanied by significant input summation in Sst neurons, but little short-term dynamics with no summation in PV neurons. Lastly, I compared the amplitude of single action potential-evoked postsynaptic responses as a function of neocortical activity level and found that it was unchanged in both neuron types. Overall, the results of this thesis provide new insights into the functioning of microcircuits in vivo while confirming many findings from reduced preparations. In the future, it will be interesting to extend these initial in vivo measurements to other neuron and synapse types, particularly in awake animals engaged in different behavioral states

The Impact of Mild Traumatic Brain injury on Neuronal Networks and Neurobehavior

Despite its enormous incidence, mild traumatic brain injury is not well understood. One aspect that needs more definition is how the mechanical energy during injury affects neural circuit function. Recent developments in cellular imaging probes provide an opportunity to assess the dynamic state of neural networks with single-cell resolution. In this dissertation, we developed imaging methods to assess the state of dissociated cortical networks exposed to mild injury. We probed the microarchitecture of an injured cortical circuit subject to two different injury levels, mild stretch (10% peak) and mild/moderate (35%). We found that mild injury produced a transient increase in calcium activity that dissipated within 1 h after injury. Alternatively, mild/moderate mechanical injury produced immediate disruption in network synchrony, loss in excitatory tone, and increased modular topology, suggesting a threshold for repair and degradation. The more significant changes in network behavior at moderate stretch are influenced by NMDA receptor activation and subsequent proteolytic changes in the neuronal populations. With the ability to analyze individual neurons in a circuit before and after injury, we identified several biomarkers that confer increased risk or protection from mechanical injury. We found that pre-injury connectivity and NMDA receptor subtype composition (NR2A and NR2B content) are important predictors of node loss and remodeling. Mechanistically, stretch injury caused a reduction in voltage-dependent Mg2+ block of the NR2B-cotaning NMDA receptors, resulting in increased uncorrelated activity both at the single channel and network level. The reduced coincidence detection of the NMDA receptor and overactivation of these receptors further impaired network function and plasticity. Given the demonstrated link between NR2B-NMDARs and mitochondrial dysfunction, we discovered that neuronal de-integration from the network is mediated through mitochondrial signaling. Finally, we bridged these network level studies with an investigation of changes in neurobehavior following blast-induced traumatic brain injury (bTBI), a form of mild TBI. We first developed and validated an open-source toolbox for automating the scoring of several common behavior tasks to study the deficits that occur following bTBI. We then specifically evaluated the role of neuronal transcription factor Elk-1 in mediating deficits following blast by exposing Elk-1 knockout mouse to equivalent blast pressure loading. Our systems-level behavior analysis showed that bTBI creates a complex change in behavior, with an increase in anxiety and loss of habituation in object recognition. Moreover, we found these behavioral deficits were eliminated in Elk-1 knockout animals exposed to blast loading. Together, we merged information from different perspectives (in silico, in vitro, and in vivo) and length scales (single channels, single-cells, networks, and animals) to study the impact of mild traumatic brain injury on neuronal networks and neurobehavior