Electrophysiology publications

The limitations of electrical neuromodulation are driving the development of neuroprosthetic systems enhanced with complementary modalities. A key technological challenge however remains the integration of the necessary hardware components (optical, thermal, fluidic, electrical) into miniaturized implants. Here we present a design framework, inspired by fast prototyping, that promises to reduce the complexity, fabrication time, and device bulk of multimodal neural interface systems. By combining extrusion‐based 3D printing of silicones and discrete electronic components, we integrated thermal neuromodulation and electrical recording capabilities in soft packages suitable for placement on the cortical surface of rodents. When linked to an autonomous auxiliary driver unit, these packages establish rapid, stable and localized hypothermia together with ElectroCorticoGraphy (ECoG) recording. In a rodent model of epilepsy (4‐aminopyridine), we demonstrate hypothermia‐induced suppression of seizure‐like activity. Our approach may advance the clinical translation of focal hypothermia as an alternative therapy for drug‐resistant focal epilepsies.

Recent work shows that the brain’s arousal system remains active during sleep, with rhythmic locus coeruleus (LC) activity shaping sleep architecture and supporting memory consolidation. The LC releases norepinephrine (NE) in infraslow (~0.02 Hz) bouts that gate NREM sleep spindles. Here, we demonstrate that heart rate (HR) fluctuations during NREM are tightly phase-locked to these NE rhythms, identifying the LC as a key driver of very-low-frequency HR variability (VLF-HRV), an understudied autonomic signal. Using optogenetics, transient LC inhibition blunts HR slowing, whereas LC activation produces rapid HR acceleration, demonstrating a direct LC-HR relationship during sleep that is maintained across a defined range of LC activity levels but breaks down when LC activity becomes excessive. We further show that infraslow HR variability is a cross-species marker of spindle-dependent memory processing. In mice, the amplitude of HR decelerations during NREM correlates with spindle activity and subsequent memory performance. Remarkably, human sleepers show the same pattern: stronger VLF-HR fluctuations during NREM correspond to increased spindle expression and better overnight memory retention. These findings reveal a mechanistic pathway through which graded changes in LC activity, up to a critical level, modulates autonomic physiology during sleep and identify infraslow HR variability as a non-invasive marker of brainstem function and memory-promoting sleep. Because LC degeneration occurs early in neurodegenerative disease, sleep-derived HR metrics may provide a scalable indicator of emerging neuromodulatory dysfunction.

The ability to detect deviations from expected sensory input is fundamental for adaptive behavior. We recorded electrocorticographic activity from the auditory (AC) and prefrontal (PFC) cortices of behaving macaques during an auditory oddball task to probe the cortical dynamics of predictive processing. Repetition of standard stimuli evoked suppression and facilitation in AC and strong low-frequency (2 Hz) enhancement in PFC, accompanied by bidirectional delta-band GC-defined interactions indicative of a shared predictive state. Deviant stimuli triggered earlier AC responses followed by PFC activation and increased GC-defined directed interactions across theta, alpha, and conventional gamma bands. Behavioral engagement amplified both repetition-related and deviance-related ECoG responses, strengthening cortical network coordination. Together, these findings reveal behaviorally gated auditory–prefrontal dynamics that are consistent with hierarchical predictive-processing accounts, while also allowing for contributions from repetition-, novelty-, and salience-related mechanisms.

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.

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.

Frontotemporal dementia (FTD) is a major cause of early-onset neurodegeneration characterized by progressive behavioral, emotional, and cognitive decline. Progranulin haploinsufficiency, a leading genetic cause of familial FTD, disrupts lysosomal function, lipid metabolism, autophagy, and neuroimmune signaling across multiple cell types. Increasing evidence indicates that microglia are particularly sensitive to progranulin loss, exhibiting elevated complement activation that contributes to TDP-43 proteinopathy and neuronal dysfunction. Here, we investigate the biological role of restoring progranulin exclusively within microglia by transplanting human induced pluripotent stem cell-derived microglia (iMG) into progranulin ( Grn )-deficient mice. We find that wild-type, but not Grn -deficient, human iMG restore brain-wide progranulin levels, normalize microglial transcriptional states, and ameliorate pathological, functional, and behavioral phenotypes associated with progranulin loss. Because microglia are the only source of progranulin in this system, these findings demonstrate that microglial progranulin is sufficient to restore key aspects of cellular, circuit, and behavioral homeostasis in a progranulin-deficient FTD model. More broadly, this work highlights a central, microglia-intrinsic role for progranulin in maintaining brain function and provides a framework for dissecting microglia-specific mechanisms across FTD and related neurodegenerative disorders.

Neurotransmitters and neuromodulators regulate brain states through diverse mechanisms, yet how their activities are coordinated during sleep remains unresolved. Using in vivo fiber photometry in adult mice expressing genetically encoded fluorescent biosensors, combined with EEG/EMG recordings, we investigated the temporal organization of multiple neuromodulators during sleep in barrel cortex, with norepinephrine (NE) as a reference signal. All five neuromodulators examined, acetylcholine, serotonin, dopamine, histamine, and NE, exhibited synchronized infraslow cortical oscillations during NREM sleep. Optogenetic suppression of locus coeruleus (LC) neurons abolished NE oscillations and selectively reduced acetylcholine fluctuations in barrel cortex, whereas targeted inhibition of basal forebrain cholinergic neurons attenuated REM-associated acetylcholine elevations without disrupting NREM-related oscillations or NE dynamics. The synchronized infraslow cortical oscillations spanning multiple neuromodulators reveal a previously unrecognized mechanism for organizing sleep architecture.

How positive and negative affective stimuli interact in the brain to influence behavioral outcomes remains poorly understood. Here, we show that recall of a positively valenced reward-associated cue (reward-conditioned stimulus, CS Rew +) can prevent or reverse fear generalization in mice. Modification of generalized fear by recall of a CS Rew + is dependent on the midbrain dopamine system and the regulation of discriminatory fear encoding by the central amygdala (CeA). Precisely timed, transient elevations in dopamine are necessary to reverse fear generalization and nondiscriminatory fear encoding in the CeA. Recall of a positive association is also effective at enhancing the extinction of a conditioned fear response in a dopamine-dependent manner. These data demonstrate that recall of a positive experience can be an effective means to suppress generalized fear and show that dopamine projections to the CeA are an important neural substrate for this phenomenon.

Foraging in the wild requires coordinated switching of critical functions, including goal-oriented navigation and context-appropriate action selection. Nevertheless, few studies have examined how different functions are represented in the brain during naturalistic foraging. To address this question, we recorded multiple single-unit activities from the medial prefrontal cortex (mPFC) of rats seeking a sucrose reward in the presence of an unpredictable attack posed by a robotic predator (Lobsterbot). Simultaneously recorded ensemble activities from neurons were analyzed in reference to various behavioral indices as the animal moved freely across the foraging area (F) between the nest (N) and the goal (E) area. An artificial neural network, trained with simultaneously recorded neural activity, estimated the rat’s current distance from the Lobsterbot. The accuracy of distance estimation was the highest in the middle F-zone in which the dominant behavior was active navigation. The spatial encoding persisted in the N-zone when non-navigational behaviors such as grooming, rearing, and sniffing were excluded. In contrast, the accuracy decreased as the animal approached the E-zone, when the activity of the same neuronal ensembles was more correlated with events related to dynamic decision-making between food procurement and Lobsterbot evasion. A population-wide analysis confirmed highly heterogeneous encoding by the region. To further assess the decision-related activity in the E-zone, a naive Bayesian classifier was trained to predict the success and failure of avoidance behavior. The classifier predicted the avoidance outcome as much as 6 s before the head withdrawal. In addition, two sub-populations of recorded units with distinct temporal dynamics contributed differently to the prediction. These findings suggest that an overlapping population of mPFC neurons may switch between two heterogeneous modes, encoding relevant locations for goal-directed navigation or an imminent situational challenge.

Memory consolidation enables animals to draw on past experiences to guide future behavior. This process involves system- and synaptic-level changes and predominantly occurs during sleep. While hippocampal-cortical circuits are well studied in this context, the contributions of other systems, including dopaminergic circuits—key players in learning-related processes—remain poorly understood. Ventral tegmental area dopaminergic (VTA DA ) neurons are active during sleep and suggested to participate in memory consolidation processes; however, causal evidence for this is lacking. Using calcium-dependent fiber photometry, electrophysiology, and chemogenetic and optogenetic manipulations across learning paradigms, we explore the functions of VTA DA neuronal activity during sleep. We show that VTA DA activity during nonrapid eye movement sleep is experience dependent, is enhanced by motor skill and associative learning, facilitates motor skill memory consolidation, and exhibits a motor learning–dependent increase in temporal coordination with cortical spindle oscillations. Our findings uncover a previously unidentified function for VTA DA neurons in consolidating memories during sleep, advancing understanding of this central neuromodulator’s functions in regulating fundamental biological processes.

The anterior-lateral motor cortex (ALM) has been extensively studied as a model for understanding the cortical mechanisms involved in planning directional movements. ALM neurons show preparatory activity that predict whether the mouse will produce a left- or right-directed lick. While the neural mechanisms underlying ALM dynamics and their links to behavior are beginning to be elucidated, the sources of this directional activity remain unclear. Here, we examined the role of ALM dopaminergic circuits in mice performing a directional licking task. We report that dopamine (DA) signals and the activity of neurons expressing D1 receptors (D1R + ) tracked the preparation and execution of licking and demonstrated a bias for planning of licks aimed at the direction contralateral to the recording site. Unilateral optogenetic manipulations of D1R + neurons or DA afferents affected lateral licking in a way consistent with their role in planning contralateral movements. Together, these results show that cortical DA modulation plays an important role in the motor preparation of directional movements.

Long-term robust intracortical microelectrode (IME) neural recording quality is negatively affected by the neuroinflammatory response following microelectrode insertion. This adversely impacts brain-machine interface (BMI) performance for patients with neurological disorders or amputations. Recent studies suggest that the leakage of blood-brain barrier (BBB) and microhemorrhage caused by IME insertions contribute to increased neuroinflammation and reduced neural recording performance. Here, we evaluated dexamethasone sodium phosphate-loaded platelet-inspired nanoparticles (DEXSPPIN) to simultaneously augment local hemostasis and serve as an implant-site targeted drug-delivery vehicle. Weekly systemic treatment or control therapy was provided to rats for 8 weeks following IME implantation, while evaluating extracellular single-unit recording performance. End-point immunohistochemistry was performed to further assess the local tissue response to the IMEs. Treatment with DEXSPPIN significantly increased the recording capabilities of IMEs compared to controls over the 8-week observation period. Immunohistochemical analyses of neuron density, activated microglia/macrophage density, astrocyte density, and BBB permeability suggested that the improved neural recording performance may be attributed to reduced neuron degeneration and neuroinflammation. Overall, we found that DEXSPPIN treatment promoted an anti-inflammatory environment that improved neuronal density and enhanced IME recording performance.

Introduction The posterior tail of the striatum receives dense inputs from sensory regions of cortex and thalamus, as well as midbrain dopaminergic innervation, providing a neural substrate for associative sensory learning. Previously, we have demonstrated that developmental hearing loss is associated with aberrant physiological states in striatal medium spiny neurons (MSNs). Methods Here we directly investigated auditory associative learning impairments in the striatum of adult Mongolian gerbils that underwent transient developmental hearing loss or sham hearing loss during the critical period of auditory development. We used electrophysiology to reveal significant changes to neuronal population responses in vivo and intrinsic and synaptic properties to medium spiny neurons in vitro as animals learned an appetitive “Go/No-Go” auditory discrimination task. For in vivo experiments a 64-channel electrode was implanted in the auditory region of the posterior tail of the striatum and neuronal recordings were carried out as animals learned the task. For in vitro experiments, corticostriatal slice preparations were made from animals on each day of training. Results In naïve animals from both groups there was limited to no phase locking to either auditory stimulus in vivo , and long term depression resulted from theta burst stimulation in vitro . Furthermore, intrinsic and synaptic properties in normal hearing animals were unaffected; however, the hearing loss group continued to show lowered synaptic inhibition, synaptic hyperexcitation, and suppressed intrinsic excitability in the hearing loss group. Starting around day 3–4 in both groups, the emergence of striatal medium spiny neuron phase locking to the auditory conditioning stimuli was observed in vivo . This occurred contemporaneous to an increased probability of theta burst induced LTP during MSN whole cell recording in vitro , and acquisition of the task as the correct rejection response significantly increased in the behaving animals. During the acquisition phase MSNs in the normal hearing group showed a significant decrease in synaptic inhibition and increase in synaptic excitation with no change to intrinsic excitability, while the MSNs in the hearing loss group showed a significant increase in synaptic inhibition, reduction of synaptic hyper excitability, and compensatory changes to intrinsic excitability that supported normal action potential generation. In both groups, synaptic properties were resolved to similar level of E/I balance that could be part of a conserved learning state. Discussion These changes to the intrinsic and synaptic properties likely support LTP induction in vivo and the strengthening of synapses between auditory inputs and MSNs that facilitate neuronal phase locking. These findings have significant implications for our understanding of striatal resilience to sensory impairments in early life, in addition to establishing a granular understanding of the striatal circuit changes that support reward driven stimulus–response learning.

Dopamine (DA)-producing neurons of the ventral tegmental area (VTA) regulate consummatory behavior in a state-dependent manner (e.g. when hungry or thirsty). The mechanisms by which and extent to which DA neurons are regulated by these interoceptive signals are poorly understood. Here, we identify transient receptor potential canonical type 6 (TRPC6) channels as selective mediators of neuropeptide receptor-induced calcium signaling in VTA-DA neurons. These channels regulate DA neuron activity and consummatory behavior in a state-dependent manner. We find that TRPC6 channels regulate distinct aspects of neuropeptide-induced calcium signals in DA neurons but make little contribution to calcium dynamics associated with metabotropic neurotransmitter receptor signaling. We further show that TRPC6 channels regulate scalable reward valuation and consummatory behavior in hungry but not thirsty mice. These findings demonstrate that neuropeptide-and neurotransmitter-activated G-protein coupled receptors (GPCRs) regulate cellular calcium dynamics through distinct mechanisms, and that TRPC6 channels are important determinants of how animals respond to different homeostatic demands.

Intracortical microelectrodes are used for recording activity from individual neurons, providing both a valuable neuroscience tool and an enabling medical technology for individuals with motor disabilities. Standard neural probes carrying the microelectrodes are rigid silicon-based structures that can penetrate the brain parenchyma to interface with the targeted neurons. Unfortunately, within weeks after implantation, neural recording quality from microelectrodes degrades, owing largely to a neuroinflammatory response. Key contributors to the neuroinflammatory response include mechanical mismatch at the device-tissue interface and oxidative stress. We developed a mechanically-adaptive, resveratrol-eluting (MARE) neural probe to mitigate both mechanical mismatch and oxidative stress and thereby promote improved neural recording quality and longevity. In this work, we demonstrate that compared to rigid silicon controls, highly-flexible MARE probes exhibit improved recording performance, more stable impedance, and a healing tissue response. With further optimization, MARE probes can serve as long-term, robust neural probes for brain-machine interface applications.

Atypical sensory processing, particularly in the auditory domain, is one of the most common and quality-of-life affecting symptoms seen in autism spectrum disorders (ASD). Fragile X Syndrome (FXS) is a leading inherited cause of ASD and a majority of FXS individuals present with auditory processing alterations. While auditory hypersensitivity is a common phenotype observed in FXS and Fmr1 knockout (KO) rodent models, it is important to consider other auditory coding impairments that could contribute to sound processing difficulties and disrupted language comprehension in FXS. We have shown previously that a Fmr1 KO rat model of FXS exhibits heightened sound sensitivity that coincided with abnormal perceptual integration of stimulus bandwidth, indicative of altered spectral processing. Frequency discrimination is a fundamental aspect of sound encoding that is important for a range of auditory processes, such as source segregation and speech comprehension, and disrupted frequency coding could thus contribute to a range of auditory issues in FXS and ASD. Here we explicitly characterized spectral processing deficits in male Fmr1 KO rats using an operant conditioning tone discrimination assay and in vivo electrophysiological recordings from the auditory cortex and inferior colliculus. We found that Fmr1 KO rats exhibited poorer frequency resolution, which corresponded with neuronal hyperactivity and broader frequency tuning in auditory cortical but not collicular neurons. Using an experimentally informed population model, we show that these cortical physiological differences can recapitulate the observed behavior discrimination deficits, with decoder performance being tightly linked to differences in cortical tuning width and signal-to-noise ratios. Together, these findings indicate that cortical hyperexcitability in Fmr1 KO rats may act to preserve signal-to-noise ratios and signal detection threshold at the expense of sound sensitivity and fine feature discrimination, highlighting a potential mechanistic locus for a range of auditory behavioral phenotypes in FXS.

During sleep, behavioral responsiveness to external stimuli is decreased. This classical definition of sleep has been applied effectively across the animal kingdom to identify this common behavioral state in a growing list of creatures, from mammals to invertebrates. Yet, it remains unclear whether decreased behavioral responsiveness during sleep is necessarily associated with decreased responsiveness in brain activity, especially in insects. Here, we performed long-term multichannel electrophysiology in tethered Drosophila melanogaster flies exposed continuously to repetitive visual stimuli. Flies were still able to sleep under these visual stimulation conditions, as determined by traditional immobility duration criteria for the field. Interestingly, we did not find any difference between responses to repetitive visual stimuli during sleep compared with wake when we recorded local field potentials (LFPs) across a transect of the fly brain from optic lobes to the central brain. However, we did find LFP responses to be altered when visual stimuli were variable and of lower probability, especially in the central brain. Central brain responses to less predictable or ‘deviant’ stimuli were lower during the deepest stage of sleep, a time of quiescence characterized by more regular proboscis extensions. This shows that the sleeping fly brain processes low-probability visual stimuli in a different way from more repeated stimuli, and presents Drosophila as a promising model for studying the potential role of sleep in regulating predictive processing.

Epidural electrical stimulation of the spinal cord (ES) is used to restore/improve locomotor movements in patients. However, the neuronal mechanisms underlying activation of locomotor networks by ES are unknown. Here, we analyzed the effects of ES on the activity of individual spinal neurons of different functional locomotor groups. Neuronal activity was recorded in decerebrate cats before and during ES that evoked locomotion. During ES initial period (NW-period, before the locomotion onset), the activity was increased in most neurons as compared to that before ES. We found that ES-caused activation of neurons of locomotor network to the average level similar to that observed during locomotion is not sufficient for initiation of locomotion. We demonstrated that the onset of ES-evoked locomotion was associated with specific changes in the activity of individual neurons within functional locomotor groups and in their responses to epidural stimuli. With the locomotion onset, there was a trend for individual neurons with extremely high activity during NW-period to decrease their activity, while for neurons with extremely low activity to become more active. Also, in neurons contributing to generation of a specific mode of locomotion, peaks and troughs in responses to individual epidural stimuli were significantly less pronounced as compared with those observed during NW-period. We suggest that these changes allow ES to maintain the high level of excitability of the locomotor network necessary for its operation without distortion of the locomotor rhythm. The obtained results advance our understanding of the neuronal mechanisms underlying activation of locomotor network by ES.

Although control of movement involves many cortical association areas, bidirectional brain-machine interfaces (BMIs) typically decode movement intent from the motor cortex and deliver feedback information to the primary somatosensory cortex (S1). Compared to the S1, the parietal and premotor areas encode more complex information about object properties, hand pre-shaping, and reach trajectories. BMIs therefore might deliver richer information to those cortical association areas than to primary areas. Here, we investigated whether instructions for a center-out task could be delivered via intracortical microstimulation (ICMS) in the anterior intraparietal area (AIP), dorsal posterior parietal cortex (dPPC), or dorsal premotor cortex (PMd) as well as the ventral premotor cortex (PMv) and S1. Two monkeys successfully learned to use AIP, PMv, or S1-ICMS instructions, but neither learned to use dPPC- or PMd-ICMS instructions. The AIP, PMv, and S1 may thus be effective cortical territory for delivering information to the brain, whereas the dPPC or PMd may be comparatively ineffective.