EEG/ECoG/EMG 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.

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.

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.

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.

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.

Homeostatic sleep regulation is essential for optimizing the amount and timing of sleep for its revitalizing function, but the mechanism underlying sleep homeostasis remains poorly understood. Here, we show that optogenetic activation of locus coeruleus (LC) noradrenergic neurons immediately increased sleep propensity following a transient wakefulness, contrasting with many other arousal-promoting neurons whose activation induces sustained wakefulness. Fiber photometry showed that repeated optogenetic or sensory stimulation caused a rapid reduction of calcium activity in LC neurons and steep declines in noradrenaline/norepinephrine (NE) release in both the LC and medial prefrontal cortex (mPFC). Knockdown of α 2 A adrenergic receptors in LC neurons mitigated the decline of NE release induced by repetitive stimulation and extended wakefulness, demonstrating an important role of α 2 A receptor–mediated auto-suppression of NE release. Together, these results suggest that functional fatigue of LC noradrenergic neurons, which reduces their wake-promoting capacity, contributes to sleep pressure.

The ability of the brain to process auditory information across multiple temporal scales is crucial for perception. This study introduces an innovative experimental approach using nonlinguistic structured stimuli composed of click trains that alternate at different rates to investigate auditory processing across 3 distinct temporal scales: individual clicks (tens of milliseconds), click trains forming auditory objects (hundreds of milliseconds), and higher-order click trains in neuronal novelty detection (seconds) in both rhesus monkeys and humans. Electrocorticography recordings in the auditory cortex of rhesus monkeys unveil the primate brain’s remarkable ability to process intricate auditory temporal patterns at timescales of tens and hundreds of milliseconds. Furthermore, extracellular recordings in monkeys demonstrate pronounced responsiveness to deviant click trains at longer temporal scales in the primary auditory cortex (A1), accompanied by synchronization with both individual clicks and click trains. By contrast, neurons in the auditory thalamus prefer individual clicks only. Notably, neurons in A1 exhibit the ability to synchronize with individual clicks while simultaneously integrating these clicks into cohesive train objects, a phenomenon we term “temporal integration during synchronization”. Additional human electroencephalography recordings complement and support these findings, highlighting the paradigm’s potential for clinical applications. Our research offers novel insights into the neural mechanisms underpinning auditory information processing across various temporal scales at the neuronal level.

Offset responses are traditionally viewed as indicators of sound cessation. Here, we investigate offset responses to auditory click trains, examining how they are modulated by inter-click intervals (ICIs) and train duration. Using extracellular recordings and electrocorticography (ECoG) in non-human primates, alongside electroencephalography (EEG) in humans, we show that offset responses are significantly influenced by both ICI and train length, thereby establishing them as markers of temporal integration. We introduce the concept of the 'Neuronal Integrative Window' (NIW), defined as the temporal span during which neurons integrate stimuli to produce or modulate the temporal integration signal. Our data reveal that on the neuronal level, the auditory cortex (AC) exhibits a more expansive NIW than the medial geniculate body (MGB), integrating stimuli over longer durations and showing a preference for larger ICIs. Furthermore, our results indicate that offset responses could serve as potential biomarkers for neurological and psychiatric conditions, highlighted by their sensitivity to pharmacological modulation with ketamine. This study advances our understanding of auditory temporal processing and proposes a novel approach for assessing and monitoring brain health.

Identifying different sleep stages in humans and other mammals has traditionally relied on electroencephalograms. Such an approach is not feasible in certain animals such as invertebrates, although these animals could also be sleeping in stages. Here, we perform long-term multichannel local field potential recordings in the brains of behaving flies undergoing spontaneous sleep bouts. We acquired consistent spatial recordings of local field potentials across multiple flies, allowing us to compare brain activity across awake and sleep periods. Using machine learning, we uncover distinct temporal stages of sleep and explore the associated spatial and spectral features across the fly brain. Further, we analyze the electrophysiological correlates of microbehaviors associated with certain sleep stages. We confirm the existence of a distinct sleep stage associated with rhythmic proboscis extensions and show that spectral features of this sleep-related behavior differ significantly from those associated with the same behavior during wakefulness, indicating a dissociation between behavior and the brain states wherein these behaviors reside.

A Rodent Sleep Spindle Detector (RSSD) application (app) was developed to assist researchers working with high volume studies examining the impact of sleep on neurological function. Our RSSD is a MATLAB-based software program with a user interface that automatically identifies sleep spindles from intracranial EEG (iEEG) recordings of rodents using two novel yet complementary algorithmic approaches, a primary and secondary one. To validate the program, 6,000 copies of real spindles of 5 different types, ranging from 11–17 Hz with a duration of at least 0.3 seconds, were randomly placed within a noisy simulated prefrontal cortex iEEG signal of 50,000 seconds in duration. When compared to the ground truth on a datapoint-by-datapoint basis (individual spindle detection), the program had an accuracy of 98.40 ± 5.62% (mean ± SD) with 95% C.I. [91.93, 100] and 96.90 ± 4.34% (mean ± SD) with 95% C.I. [91.91, 100] for the primary and secondary algorithmic approach, respectively. Evaluating total spindle count, the program had an accuracy of 93.68 ± 13.66% (mean ± SD) with 95% C.I. [81.71, 100], and of 99.85 ± 0.12% (mean ± SD) with 95% C.I. [99.71, 99.96] for the primary and secondary algorithmic approach, respectively. The robustness of the sleep spindle detection was further validated for a range of spindle's duration, amplitude, and frequency by embedding in the iEEG signal respective artificial spindles. Finally, the RSSD app further improves its performance by first processing available video recordings of rodents to identify periods of quiescence and then running the sleep spindle detection algorithms on the iEEG only for those periods.

The kindling model has been used extensively by researchers to study the neurobiology of temporal lobe epilepsy (TLE) due to its capacity to induce intensification of seizures by the progressive recruitment of additional neuronal clusters into epileptogenic networks. We applied repetitive focal optogenetic activation of putative excitatory neurons in the dorsal CA1 area of the hippocampus of mice to investigate the role of inhibitory signaling during this process. This experimental protocol resulted in a kindling phenotype that was maintained for 2 weeks after the animals were fully kindled. As a result of the different phases of optogenetic kindling (OpK), key inhibitory signaling elements, such as KCC2 and NKCC1, exhibited distinct temporal and spatial dynamics of regulation. These alterations in protein expression were related to the distinct pattern of ictal activity propagation through the different hippocampal sublayers. Our results suggest the KCC2 disruption in the contralateral hippocampus of fully kindled animals progressively facilitated the creation of pathological pathways for seizure propagation through the hippocampal network. Upon completion of kindling, we observed animals that were restimulated after a rest period of 14-day showed, besides a persistent KCC2 downregulation, an NKCC1 upregulation in the bilateral dentate gyrus and hippocampus-wide loss of parvalbumin-positive interneurons. These alterations observed in the chronic phase of OpK suggest that the hippocampus of rekindled animals continued to undergo self-modifications during the rest period. The changes resulting from this period suggest the possibility of the development of a mirror focus on the hippocampus contralateral to the site of optical stimulations. Our results offer perspectives for preventing the recruitment and conversion of healthy neuronal networks into epileptogenic ones among patients with epilepsy.

Information transfer within neuronal circuits depends on the balance and recurrent activity of excitatory and inhibitory neurotransmission. Chloride (Cl − ) is the major central nervous system (CNS) anion mediating inhibitory neurotransmission. Astrocytes are key homoeostatic glial cells populating the CNS, although the role of these cells in regulating excitatory-inhibitory balance remains unexplored. Here we show that astrocytes act as a dynamic Cl − reservoir regulating Cl − homoeostasis in the CNS. We found that intracellular chloride concentration ([Cl − ] i ) in astrocytes is high and stable during sleep. In awake mice astrocytic [Cl − ] i is lower and exhibits large fluctuation in response to both sensory input and motor activity. Optogenetic manipulation of astrocytic [Cl − ] i directly modulates neuronal activity during locomotion or whisker stimulation. Astrocytes thus serve as a dynamic source of extracellular Cl − available for GABAergic transmission in awake mice, which represents a mechanism for modulation of the inhibitory tone during sustained neuronal activity.

There is growing evidence on the efficacy of electrical stimulation delivered via spinal neural interfaces to improve functional recovery following spinal cord injury. For such interfaces, carbon-based neural arrays are fast becoming recognized as a compelling material and platform due to biocompatibility and long-term electrochemical stability. Here, we introduce the design, fabrication, and in vivo characterization of a novel cervical epidural implant with carbon-based surface electrodes. Through finite element analysis and mechanical load tests, we demonstrated that the array could safely withstand loads applied to it during implantation and natural movement of the subject with minimal stress levels. Furthermore, the long-term in vivo performance of this neural array consisting of glassy carbon surface electrodes was investigated through acute and chronic spinal motor evoked potential recordings and electrode impedance tests in rats. We demonstrated stable stimulation performance for at least four weeks in a rat model of spinal cord injury. Lastly, we found that impedance measurements on all carbon-based spinal arrays were generally stable over time up to four weeks after implantation, with a slight increase in impedance in subsequent weeks when tested in spinally injured rats. Taken together, this study demonstrated the potential for carbon-based electrodes as a spinal neural interface to accelerate both mechanistic research and functional restoration in animal models of spinal cord injury.

Microglia are critical regulators of brain development that engulf synaptic proteins during postnatal synapse remodeling. However, the mechanisms through which microglia sense the brain environment are not well defined. Here, we characterized the regulatory program downstream of interleukin-33 (IL-33), a cytokine that promotes microglial synapse remodeling. Exposing the developing brain to a supraphysiological dose of IL-33 altered the microglial enhancer landscape and increased binding of stimulus-dependent transcription factors including AP-1/FOS. This induced a gene expression program enriched for the expression of pattern recognition receptors, including the scavenger receptor MARCO. CNS-specific deletion of IL-33 led to increased excitatory/inhibitory synaptic balance, spontaneous absence-like epileptiform activity in juvenile mice, and increased seizure susceptibility in response to chemoconvulsants. We found that MARCO promoted synapse engulfment, and Marco-deficient animals had excess thalamic excitatory synapses and increased seizure susceptibility. Taken together, these data define coordinated epigenetic and functional changes in microglia and uncover pattern recognition receptors as potential regulators of postnatal synaptic refinement.

The cerebral cortex is spontaneously active during sleep, yet it is unclear how this global cortical activity is spatiotemporally organized, and whether such activity not only reflects sleep states but also contributes to sleep state switching. Here we report that cortex-wide calcium imaging in mice revealed distinct sleep stage-dependent spatiotemporal patterns of global cortical activity, and modulation of such patterns could regulate sleep state switching. In particular, elevated activation in the occipital cortical regions (including the retrosplenial cortex and visual areas) became dominant during rapid-eye-movement (REM) sleep. Furthermore, such pontogeniculooccipital (PGO) wave-like activity was associated with transitions to REM sleep, and optogenetic inhibition of occipital activity strongly promoted deep sleep by suppressing the NREM-to-REM transition. Thus, whereas subcortical networks are critical for initiating and maintaining sleep and wakefulness states, distinct global cortical activity also plays an active role in controlling sleep states.

The nucleus reuniens (RE) is necessary for memories dependent on the interaction between the medial prefrontal cortex (mPFC) and hippocampus (HPC). One example is trace eyeblink conditioning, in which the mPFC exhibits differential activity to neutral conditioned stimuli (CS) depending on their contingency with an aversive unconditioned stimulus (US). To test if this relevancy signal is routed to the RE, we photometrically recorded mPFC axon terminals within the RE and tracked their changes with learning. As a comparison, we measured prefrontal terminal activity in the mediodorsal thalamus (MD), which lacks connectivity with the HPC. In naïve male rats, prefrontal terminals within the RE were not strongly activated by tone or light. As the rats associated one of the stimuli (CS+) with the US, terminals gradually increased their response to the CS+ but not the other stimulus (CS-). In contrast, stimulus-evoked responses of prefrontal terminals within the MD were strong even before conditioning. They also became augmented only to the CS+ in the first conditioning session; however, the degree of activity differentiation did not improve with learning. These findings suggest that associative learning selectively increased mPFC output to the RE, signaling the behavioral relevance of sensory stimuli.