Electrophysiology publications

Mafb and c-Maf transcription factors (TFs) are expressed in medial ganglionic eminence (MGE) lineages, beginning in progenitors and continuing into mature GABAergic parvalbumin-positive (PV + ) and somatostatin-positive (SST + ) cortical interneurons (CINs). Deleting Mafb and c-Maf in MGE before SST versus PV fate specification causes developmental anomalies, including altered numbers of CINs and seizure phenotypes, but the specific contributions of these TFs in postmitotic SST + and PV + CINs to epilepsy remain unknown. To address this, we conditionally deleted Mafb or c-Maf in SST + or PV + interneurons after interneuron fate specification in female and male mice. Deletion of c-Maf, but not Mafb, in SST+ cells was associated with reduced synaptic excitation onto these cells and with spontaneous spike-and-wave discharges, consistent with absence-like seizures. In contrast, deletion of Mafb in SST + CINs reduced their density in superficial cortical layers but did not induce epilepsy. Neither c-Maf nor Mafb deletion in PV + CINs produced major electrophysiological or histological abnormalities in the somatosensory cortex. These findings identify a specific requirement for c-Maf in modulating synaptic excitation of SST + interneurons and show that its loss in SST + cells is associated with the development of absence-like epileptiform activity in vivo. Together, our results refine the understanding of how transcriptional programs shape interneuron function in the mature cortex and highlight c-Maf/MAF-dependent pathways as candidates for investigation in epilepsy genetics.

Platinum electrodes are used in many bionic devices; however, they have limited charge injection capacity (CIC) and signal‐to‐noise ratio (SNR), restricting performance. Iridium oxide has substantially larger CIC and reduced impedance compared to platinum. While these types of electrochemical measurements are typically used to infer improved electrophysiological performance, there are no studies demonstrating this correlation. This article compares the electrochemical and acute electrophysiological recording performance of iridium and electrochemically activated IrOx. Increased iridium activation reduced total impedance at low‐intermediate frequencies and steady‐state electroactive area but had no impact on linear diffusion electroactive area. The total impedance had a poor correlation with background noise, SNR and spike count. The results contribute to the previous literature indicating linear diffusion electroactive area determines the number of neurons within recording distance of the electrode, impacting SNR and spike count. Measurements of impedance are mainly of benefit as an indirect measure of linear diffusion electroactive area, in which case the measurement and analysis must be performed appropriately. A wide range of IrOx activation states can be produced with increased CIC, without concern of neural recording performance impacts. However, higher oxidation states resulting in electrode dissolution or increase in electrode resistance may limit IrOx chronic performance.

Pain management strategies have progressed beyond traditional pharmacologic and physical interventions, integrating advanced neuromodulation techniques such as deep brain stimulation, peripheral nerve stimulation, and high‐frequency spinal cord stimulation (hSCS). Despite its clinical efficacy, the supraspinal mechanisms underlying hSCS remain poorly understood. Prior work in sheep demonstrated that hSCS modulates gamma (γ) band (70–150 Hz) activity in the primary somatosensory and association cortices, implicating cortical involvement in pain modulation. Given the interaction between low‐ and high‐oscillations, we hypothesized that hSCS modulates γ activity in a region‐ and time‐dependent manner through specific coupling with theta rhythms (θ, 4–8 Hz). To test this, we quantified θ–γ phase‐amplitude coupling (PAC) during tibial nerve stimulation (TNS) before (TNS 0 ) and after (TNS 1 ) hSCS to assess cortical processing of TNS‐evoked activity, while recording cortical (association and somatosensory cortices) neural activity using 96‐channel subdural electrocorticography (ECoG). We then computed the corresponding modulation index (MI) to quantify PAC strength. While the preferred θ phase of γ activity remained consistent across conditions in both cortical areas, θ‐γ coupling was more robust and stable in the association than the somatosensory cortex. However, MI increased significantly post‐hSCS in both cortices, indicating enhanced θ‐γ coupling during TNS 1 . Temporally, both cortices showed distinct response patterns: the somatosensory cortex exhibited strongest coupling increase early post‐hSCS, followed by a progressive decline, whereas the association cortex showed a more delayed and temporally distributed enhancement. These findings indicate that hSCS modulates cortical cross‐frequency interactions during TNS‐evoked sensory processing, wherein somatosensory and association cortices show distinct temporal coupling dynamics that may contribute to supraspinal mechanisms of pain modulation.

Introduction: Transcranial focused ultrasound (tFUS) can noninvasively modulate sensory pathways, but the cell-type-specific mechanisms underlying excitatory or inhibitory effects remain unclear. Here, we investigate how tFUS applied to the somatosensory cortex (S1) influences S1 and posterior medial thalamic nucleus (POm) responses to hind paw vibration-tactile stimulation and which neuronal populations mediate these effects. Methods: Vibration-tactile stimulation evoked potentials (TEPs) and multi-unit activity (MUA) in S1 and POm were recorded from male rats. Optogenetic tagging was used to identify S1 CaMKII-positive, PV-positive, and SST-positive neurons, while waveform features were used to classify putative excitatory (i.e., regular-spiking units - RSUs) and inhibitory neurons (i.e., fast-spiking units - FSUs) in POm. Results: We found that only S1 CaMKII-positive neurons and POm RSUs responded robustly to tactile stimulation. When tFUS was applied to S1, high pulse repetition frequency (PRF), high duty cycle, and high-pressure stimulation (etFUS) produced excitatory modulation of the sensory pathway, whereas low PRF, low duty cycle, and low-pressure stimulation (itFUS) induced inhibitory effects. Further analyses suggested that excitatory modulation may involve activation of S1 CaMKII-positive neurons, while the inhibitory effect may be associated with their deactivation. Conclusions: These findings demonstrate that tFUS exerts bidirectional, parameter-dependent modulation of a sensory pathway and highlight the critical role of CaMKII-positive neurons in mediating these effects. This study provides mechanistic insight into cell-type-specific neuromodulation by tFUS, particularly in bidirectional modulation of a sensory pathway, and informs the optimization of stimulation parameters for targeted therapeutic interventions.

Neonatal bilirubin encephalopathy is primarily characterized by central auditory dysfunction and cognitive impairments. However, the precise molecular mechanisms underlying bilirubin-induced neurotoxicity remain poorly understood, hindering the development of effective therapeutic strategies. Using kinase activity prediction tools based on quantitative phosphoproteomics, we identified ROCK2 (Rho-associated protein kinase 2) as a critical kinase regulating the phosphorylation of proteins associated with bilirubin exposure. Molecular docking and MicroScale Thermophoresis assays revealed a strong binding affinity between bilirubin and ROCK2. Interestingly, bilirubin increased ROCK2 protein expression without affecting its mRNA levels, and cycloheximide chase assays revealed enhanced ROCK2 stability, implicating post-translational regulation. While bilirubin did not directly activate ROCK2 kinase activity in vitro, it elevated phosphorylation of its substrate LIMK1, suggesting that ROCK2 accumulation amplifies downstream signaling. In primary rat neurons, ROCK2 inhibitors (Belumosudil and Y-27632) ameliorated bilirubin-induced loss of mitochondrial membrane potential and neuronal cell death. Furthermore, using ROCK2 inhibitors and Rock2+/- mice, we demonstrated that modulation of ROCK2 significantly alleviated bilirubin-induced auditory deficits and cognitive impairments. These behavioral improvements were linked to restored excitatory synaptic transmission in the cochlear nucleus and reduced dendritic damage in hippocampal neurons. These findings position ROCK2 as a promising molecular target for therapeutic intervention in bilirubin encephalopathy.

Chronic sleep disruption and cognitive deficits are debilitating long-term consequences of traumatic brain injury (TBI), yet the endogenous mechanisms that drive network-level recovery remain poorly understood. Here, we demonstrate that during the chronic phase post-injury, network oscillations critical for memory, including slow oscillations, delta waves, and sleep spindles, undergo precise adaptive tuning that sustains sleep-dependent memory consolidation. This functional circuit resilience requires Semaphorin-3A (Sema3a); loss of Sema3a function prevents the protective reorganization of non-rapid eye movement (NREM) sleep architecture, impairs sleep-dependent memory consolidation, and exacerbates cortical lesion size. Together, these findings identify Sema3a as an innate protective mechanism that preserves sleep architecture and cognitive function following TBI.

Age‐related vestibular dysfunction (ARVD) is a prevalent and debilitating condition among the elderly, yet its etiology and underlying molecular mechanisms remain poorly understood. We focused on mechanosensitive hair cells (HCs), which are widely recognized as susceptible to aging. Using single‐cell RNA‐seq transcriptomic analysis of young and old mice, we show that old vestibular HCs exhibit conserved transcriptomic hallmarks of cellular aging, including cellular senescence, mitochondrial dysfunction, and impaired proteostasis, along with prominent cell type‐specific changes linked to hair bundle architecture and the mechanotransduction machinery. Consistent with these transcriptomic findings, imaging and electrophysiological recordings from old vestibular sensory epithelia reveal hair bundle degeneration and reduced mechanotransduction activity. Importantly, this structural and functional deterioration precedes HC loss, underscoring impaired hair bundle function as a key driver of ARVD. Furthermore, our comparative analysis identifies both shared and distinct aging signatures in vestibular and cochlear HCs, providing broader insight into the mechanisms that may underlie their different rates of age‐related degeneration.

Current disease-sensing devices primarily focus on distinguishing between healthy and diseased states, effective for diagnosis but limited in guiding optimal intervention timing for prevention. We developed a tripartite framework identifying pre-disease state in depression, a reversible phase preceding irreversible onset. Using complex systems theory, we analyzed early-warning signals emerging as biological systems approach critical transitions. Continuous monitoring of nine multimodal biomarkers—spanning electrophysiological, behavioral, and biological—enabled classification into normal, pre-disease, and disease states by quantitatively defining critical points. An artificial intelligence agent classified disease states with 95.2% accuracy using multimodal data, enabled by ultrasoft neural probes for stable, low-damage recordings. Therapeutic validation with a skin-attachable wireless vagus nerve stimulator integrating soft three-dimensional electrodes demonstrated superior efficacy during pre-disease states. Subjects treated during pre-disease showed faster recovery and greater therapeutic responses, while those treated after disease onset failed to achieve full recovery. This framework provides evidence-based rationale for early intervention.

Objective To evaluate the feasibility of using the acoustic change complex (ACC) as an objective cortical marker of continuous speech sound discrimination using connected Ling-six stimuli. Design Cortical auditory evoked potentials were recorded from 10 young adults with normal hearing using a continuous, pause-free sequence of the six Ling phonemes (/u-a-i-ʃ-s-m/). ACC responses were recorded in a passive listening paradigm with minimal electrodes. Reproducibility was assessed in a subset of participants retested 1 year later. Results Robust ACC responses were elicited for all six phonemic transitions in every participant, indicating reliable cortical discrimination within the continuous speech stream. Although response morphology varied across listeners, within-subject responses demonstrated strong reproducibility over a one-year interval (mean cross-correlation = 0.95). Conclusion Continuous Ling-six stimuli reliably evoke ACC responses reflecting cortical speech sound discrimination. This efficient and repeatable paradigm shows promise as an objective verification tool for auditory learning and sound discrimination, particularly in populations for whom behavioral assessment is unreliable.

In mammals, slow-wave sleep is characterized by synchronized neuronal activity that alternates between on and off periods. Slow-wave activity (SWA) and synchrony reflect sleep need, are correlated with synaptic strength in cortical circuits and promote synaptic downselection and memory consolidation. Here we assessed whether these core benefits of sleep can be obtained during waking. We locally induced alternating on/off periods during wakefulness using optogenetics in mice. This led to a local ipsilateral reduction in SWA and synchrony during subsequent sleep, and to reduced markers of synaptic strength. Moreover, bilateral induction of off periods over sensorimotor cortex during sleep deprivation restored memory consolidation. Thus, inducing on/off activity during wakefulness is sufficient to reduce local sleep need and fulfill core functions of sleep.

Adaptive behavior requires that behaviorally relevant signals gain access to neural circuits guiding action. The thalamus has long been proposed to regulate information flow to cortical and subcortical systems, yet whether it also tracks internally generated goal signals remains unclear. Here, we show that neurons in the paraventricular thalamus (PVT) projecting to the nucleus accumbens (NAc) encode the motivational value of safety during active avoidance. As mice learn to avoid threat, PVT→NAc neurons develop a signal that emerges selectively at successful avoidance, is experience-dependent, and diminishes following outcome devaluation. Selective silencing of the PVT→NAc pathway at safety onset reduces the motivational value assigned to safety without impairing action–outcome learning. Mechanistically, PVT input engages cholinergic interneurons (CIN) in the NAc to regulate dopamine release via synaptic potentiation mediated by GluA2-lacking AMPA receptors at PVT–CIN synapses. Disrupting this plasticity reduces the motivational impact of safety. These findings identify a thalamostriatal mechanism through which learned goals gain stable access to motivational circuitry.

CLN3 disease, the most common form of the Neuronal Ceroid Lipofuscinoses (NCLs), causes progressive cognitive decline and language impairment in humans. A pathological hallmark is the accumulation of storage material within neuronal lysosomes resulting from mutations in the CLN3 gene. We previously identified parallel deficits in auditory duration mismatch negativity (MMN), an electroencephalography (EEG)-based marker of auditory change detection, in individuals with CLN3 disease and in Cln3 -/- mice. MMN-dependent auditory change detection relies on sensory-memory comparison mechanisms. However, the anatomical and neurophysiological substrates underlying this response in CLN3 disease remain unclear. Here, we investigated central auditory dysfunction in Cln3 -/- mice by integrating immunohistochemical mapping of lysosomal storage pathology, using the canonical marker Subunit C of Mitochondrial ATP Synthase (SCMAS), with EEG analysis of auditory evoked potentials (AEPs). Neuropathological analyses revealed age-dependent and sex-divergent SCMAS accumulation across the auditory thalamocortical circuit, including the excitatory auditory thalamus, the inhibitory thalamic reticular nucleus, and the primary auditory cortex. In parallel, Cln3 -/- mice exhibited age- and sex-dependent alterations in AEPs relative to wild-type controls. Importantly, an integrated measure of auditory thalamocortical SCMAS accumulation accounted for a substantial portion of age- and sex-matched variation in AEP responses, with stronger associations for the early N1 component than the later MMN component. Together, these findings link age-dependent and sex-divergent auditory neurophysiological deficits to region-specific lysosomal storage pathology within the auditory thalamocortical circuit in the Cln3 -/- mouse model. This integrated functional-anatomical framework provides insight into circuit vulnerability and supports the development of translational neurophysiological biomarkers for CLN3 disease. Graphical Abstract Highlights SCMAS accumulates across the auditory thalamocortical circuit in Cln3 -/- mice Accumulation shows distinct age- and sex-dependent regional trajectories Cln3 -/- mice exhibit progressive alterations in auditory evoked potentials Thalamic pathology is strongly associated with the early auditory N1 response Histology–EEG integration links circuit pathology to auditory dysfunction

Mutations in Myo7a cause Usher syndrome type 1B and non-syndromic deafness, but the precise function of MYO7A in sensory hair cells remains unclear. Using long-read sequencing, we identify and characterize a novel isoform, MYO7A-N, expressed in auditory hair cells alongside the canonical MYO7A-C. Isoform-specific knock-in mouse models reveal that inner hair cells primarily express MYO7A-C, while outer hair cells express both isoforms in opposing tonotopic gradients. Both isoforms are localized to the upper tip-link insertion site, consistent with a role in the tip link for mechanotransduction. Loss of MYO7A-N leads to outer hair cell degeneration and progressive hearing loss. Cryo-EM structures reveal isoform-specific differences at actomyosin interfaces, correlating with distinct ATPase activities. These findings reveal an unexpected layer of molecular diversity within the mechanotransduction machinery. We propose that MYO7A isoform specialization enables fine-tuning of tip-link tension, thus hearing sensitivity, and contributes to the frequency-resolving power of the cochlea.

We describe properties and laminar organization of visual and auditory responses sampled with linear electrode arrays in and around the supplementary eye field of four macaque monkeys performing a visually guided task with a tone secondary reinforcer. Of pyramidal neurons in all layers and interneurons in L3 and L5/6, one-quarter were visually responsive, one-quarter, auditory, with 30% bimodal. Visual neurons were less common rostral, lateral, and medial to the supplementary eye field. Facilitated visual and auditory responses were much more common than suppressed. Pyramidal and interneurons responded to the stimulus in either hemifield with a weak bias for contralateral targets. Visual response latencies were comparable to values previously reported and later than auditory responses. Facilitated visual responses of interneurons preceded those of pyramidal neurons. Transient visual responses preceded sustained. Current-source density revealed visually evoked current sinks after auditory sinks that were transient for bright flashes and prolonged for the discrete task target. The earliest sink appeared at the L3 to L5 border and spread superficially and deeper with idiosyncratic variability across monkeys. These findings reveal new details about sensory processing in medial frontal cortex and complement our previous descriptions of the functional properties and laminar organization of neurons supporting cognitive control.

A central goal in neuroscience is to develop cross-species frameworks that reveal conserved principles of movement control. Recent work has suggested a potential species difference in the role of primary motor cortex (M1) during skilled forelimb tasks: in rodents, extensive practice appears to shift control to subcortical circuits, leading to "disengagement" of M1 from task execution. Importantly, there is no evidence of such disengagement in macaques. We hypothesized that these differences instead reflect task demands, particularly the need for fine (i.e., grasping) versus gross motor control. Strikingly, M1 lesions in macaques produced recovery patterns similar to rodents: gross motor control, including an exclusively gross motor task, recovered rapidly, whereas fine motor control exhibited persistent deficits. Detailed kinematic analyses in both macaques and mice performing a single-pellet reach-to-grasp task (RGT) revealed analogous disruptions in the temporal structure of sub-movements. These findings underscore the importance of task design and the translational value of rodent models for understanding motor control and recovery.

Nervous systems generate predictions using internal copies of motor commands, termed corollary discharge (CD). CD modulates sensory neurons to distinguish self-generated sensory inputs (reafference) from external inputs (exafference). As behavior changes throughout development and evolution, these predictions must update as reafference changes. However, mechanisms that synchronize CD to reafferent input remain unknown. Mormyrid fish communicate using electric organ discharges (EODs). To distinguish reafferent and exafferent EODs, a CD inhibits sensory neurons whenever a reafferent EOD is produced. EOD duration varies across and within species, and a yet-unknown mechanism precisely time-locks inhibition with reafference. Likewise, seasonal increases in testosterone reversibly elongate male EODs in some species, and testosterone shifts CD timing to match changing reafference. To identify the neural substrates of hormonal CD shifts, we treated Brienomyrus brachyistius with testosterone and recorded field potentials from six nuclei linking electromotor, CD, and electrosensory pathways. Testosterone delayed and elongated field potentials in the mesencephalic command-associated nucleus (MCA) of the CD pathway, which shifted downstream activity. We identified substrates of evolutionary and age-related shifts in two species of Campylomormyrus with dramatically different EODs: one with short-duration EODs and one with long EODs that can elongate as individuals age. Both inter- and intraspecies EOD variation was associated with the onset and duration of MCA field potentials. We find distinct processes-hormonal plasticity over days, age-related changes over years, and evolutionary divergence-converge on a common substrate to synchronize CD with reafference. This suggests that sensorimotor systems can evolve a shared solution for temporal coordination across timescales.

Stem cell therapy has been widely studied as a promising treatment for spinal cord injury (SCI). However, a lack of functional scaffolds for stem cell therapy to address SCI leads to low therapeutic efficacy due to poor survival of transplanted cells. To address these challenges, this study aims to enhance regenerative potential of spinal cord organoids (SCOs) by employing extracellular matrix (ECM) recapitulating spinal cord-specific microenvironment. Decellularized spinal cord-derived ECM (ScEM) supports 3D culture for development, maturation, and functionality of human induced pluripotent stem cell-derived SCOs, comparable to standard organoid culture matrix such as Matrigel. Transplantation of SCOs using ScEM hydrogel promotes axonal regeneration with neovascularization in lesions, likely because of enhanced engraftment and integration of transplanted SCOs into defective tissues facilitated by ScEM. Accordingly, this approach induces early locomotor recovery of animals with SCI. These findings suggest that functional ECM scaffold capable of providing microenvironmental complexity of spinal cord can potentiate organoid-based therapeutics for SCI treatment.

Contextual encoding in the dorsal hippocampus (DHPC) may recruit hypothalamic feeding modules to calibrate eating across environments, but the mechanistic instantiation of cells and circuits that undergird these processes is limited. Single-cell transcriptomics and transsynaptic tracing of the dorsolateral septum (DLS) identified an evolutionarily conserved prodynorphin (Pdyn)-expressing subpopulation of somatostatin (Sst)-expressing inhibitory neurons that receives dense dorsal, but not ventral, hippocampal inputs. Circuit optogenetics, electrophysiology, and in vivo calcium imaging demonstrated that DLS(Pdyn) neurons inhibit GABAergic neurons of the lateral hypothalamic area (LHA), exhibit context-dependent neural responses to food rewards and aversive stimuli, and confer contextual and internal state-dependent calibration of feeding. Viral deletion of Pdyn in the DLS impaired context-dependent food reward consumption, suggesting a role for dynorphin/kappa opioid receptor signaling in these processes. Together, our findings highlight how ancient LHA feeding circuits integrate DHPC input through DLS(Pdyn) inhibitory neurons to link context with regulation of food consumption.

Implantable microelectrode arrays (MEAs) are powerful tools for neurophysiological studies and hold tremendous potential as a key component of clinical neuroprostheses. However, their long-term efficacy is hampered by inflammatory responses to implantation. This study examines the impact of MEA substrate rigidity on neural recording quality and inflammatory tissue responses. We implanted stiff silicon-based and flexible polyimide-based MEAs with similar geometries in the deep brain region of the mouse striatum and performed weekly impedance and electrophysiological measurements over 4 weeks. The flexible MEAs demonstrated more reliable recording quality in terms of stable signal-to-noise ratio, single-unit yield, peak-to-peak amplitude, noise, and impedance, compared to the stiff probes, whose performance deteriorated over time. Endpoint histological analyses were performed to assess the glial scarring (Iba-1, GFAP), blood-brain barrier integrity (IgG), mechanosensitive ion channel expression (Piezo1), and neuronal population (NeuN and NF200) around the implant site. We found reduced microglial activation and IgG fouling within a 50-μm radius around the flexible MEAs compared to the stiff group. Additionally, a higher expression of Piezo1 was observed localized around the stiff MEA, correlating positively with increased Iba-1 and GFAP intensity. Our results show that flexible MEAs have improved device-tissue integration, indicated by lower inflammation levels and better recording stability. This research underscores the critical role of MEA substrate rigidity in influencing adverse tissue reactions, especially for deep brain regions. This understanding will improve our ability to design stable and reliable devices for chronic neural interface devices and beyond.

The neural response of the brainstem to brief sounds, known as the auditory brainstem response (ABR), is widely employed in the laboratory and the clinic to diagnose hearing loss. Current ABR approaches are limited to analyzing the average ABR to hundreds of stimulus trials. Historically, trial-by-trial ABR analysis has not been possible owing to each trial's small signal-to-noise ratio. Here we overcome this limitation and show how to score individual ABR trials. We use the distribution of individual-trial ABR scores to define thresholds, which we call auditory brainstem detection (ABD) thresholds, and to assess suprathreshold hearing. Scores based on individual-trial amplitude and similarity produce lower ABD thresholds than scores based on individual-trial amplitude alone. Our method enables us to rank the suprathreshold hearing of individual subjects. Despite having normal ABR thresholds, some subjects appear to have suprathreshold hearing deficits.