Electrophysiology publications

One of the most distinctive features of the mammalian cerebral cortex is its laminar structure. Of all cortical layers, layer 6b (L6b) is by far the least studied, despite exhibiting direct sensitivity to orexin and having widespread connectivity, suggesting an important role in regulating cortical oscillations and brain state. We performed chronic electroencephalogram (EEG) recordings in mice in which a subset of L6b neurons was conditionally ‘silenced’, during undisturbed conditions, after sleep deprivation (SD), and after intracerebroventricular (ICV) administration of orexin. While the total amount of waking and sleep or the response to SD were not altered, L6b-silenced mice showed a slowing of theta frequency (6–9 Hz) during wake and rapid eye movement (REM) sleep, and a marked reduction of total EEG power, especially in non-rapid eye movement (NREM) sleep. The infusion of orexin A increased wakefulness in both genotypes, but subsequent levels of EEG slow-wave activity during NREM sleep were lower in L6b-silenced animals in the occipital derivation. In summary, these results demonstrate a role for cortical L6b in state-dependent brain oscillations and in the response to orexinergic neurotransmission. Our findings provide new insights in functions of L6b neurons and could inform the understanding of abnormal regulation of brain states in neurodevelopmental and psychiatric disorders.

Neuromodulation is widely employed to enhance neural activity and restore impaired circuitry, yet current methods suffer from invasiveness, limited depth, or poor spatial resolution. Temporal interference stimulation (TIS) has emerged as a non-invasive approach to modulate deep brain regions via interference of high-frequency electric fields, achieving spatial selectivity. Despite its potential, the physiological effects remain unexplored. Here, we present a customized liquid metal-based neural interface to record electrophysiological responses to TIS across diverse neural tissues, from brain organoids to mouse brains. The softness of the interface minimizes invasiveness while ensuring stable access to deep neural regions. Electrophysiological analyses reveal TIS-induced dynamics in neurodevelopment and functional connectivity. Furthermore, we investigated latent neural dynamics, presenting population-level neural activity, to compare responses across models of differing complexity and maturity. By combining soft neural interfaces with multi-scale analyses, this study uncovers how neuromodulation shapes neural dynamics and supports the development of future therapeutic strategies.

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.

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.

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.

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.

A hallmark of intelligence is proficiency in solving new problems, including those that substantially differ from previously seen problems. Problem solving in turn depends on the goal-directed generation of novel ideas and behaviours 1 , which has been proposed to involve internal representations of discrete units (or symbols) that can be recombined into numerous possible composite representations 1–7 . Although this view has been influential in cognitive-level explanations of behaviour, definitive evidence for a neuronal substrate of symbols has remained elusive. Here we identify a neural population that encodes action symbols—recombinable representations of discrete units of motor behaviour—in a specific area of the frontal cortex. In macaque monkeys performing a drawing-like task, we found behavioural evidence that action elements (strokes) exhibit three crucial features that indicate an underlying symbolic representation: (1) invariance over low-level motor parameters; (2) categorical structure, which reflects discrete action types; and (3) recombination into novel sequences. Based on simultaneous neural recordings across eight regions of the motor, premotor and prefrontal cortex, we identified population activity specifically in the ventral premotor cortex that encodes planned actions in a manner that also reflects invariance, categorical structure and recombination. These findings reveal a neural representation of action symbols localized to the ventral premotor cortex and a putative neural substrate for symbolic operations.

Sensory experience refines neural circuits during critical periods of postnatal development 1–3 . Although neuronal activity is known to orchestrate the circuit wiring that underlies this process 4,5 , the environmental cues that restrain developmental plasticity as animals mature are less clear. Here we examine the experience-dependent maturation of the mouse primary visual cortex across postnatal development using paired single-cell transcriptomic and chromatin accessibility sequencing. In addition to identifying the activity-dependent gene programs that emerge within each cortical cell type, we find that light exposure drives astrocyte maturation through cell-type-specific recruitment of the glucocorticoid receptor (encoded by Nr3c1 ) to chromatin. Astrocyte glucocorticoid receptor signalling activates an extensive gene regulatory program that is partially conserved in human brain development and promotes maturation processes that may regulate critical period closure. Collectively, these findings reveal that astrocyte glucocorticoid receptor signalling restricts neuronal plasticity. Glucocorticoid regulation of astrocyte maturation may also contribute to the effects of early-life stress across the brain, and the disruption of this process may increase susceptibility to neuropsychiatric disease.

Transient high-frequency activity (HFA) in local field potentials exhibits substantial variability across trials and behavioral states, yet its functional role in sensory representation remains poorly understood. Here, we tested whether transient HFA events carry stimulus-related information through their temporal, spectral, and phase-dependent properties. Using intracranial recordings from 21 human participants performing a visual localizer task, we extracted transient HFA events and quantified their features using information-theoretic and decoding analyses. Individual event features carried only modest information about stimulus identity, and response magnitude and morphology-related properties contributed minimally to decoding performance. Instead, decoding was dominated by temporal alignment and low-frequency phase. Critically, representing transient events as distributed low-frequency phase configurations across electrodes substantially improved cross-trial decoding performance, whereas disrupting distributed phase structure eliminated this decoding advantage. These findings indicate that stimulus-related structure in transient HFA does not primarily arise from isolated local event properties, but instead emerges through distributed, phase-dependent network dynamics. More broadly, the results provide a framework for understanding how transient high-frequency neural activity contributes to sensory representations across distributed cortical networks.

Cognitive impairments are common in absence epilepsy, yet the neural basis of these deficits remains largely unknown. Communication between the thalamic reuniens nucleus and the prefrontal cortex is critical for flexible behavior. Here, we identify a disruption of this pathway in mice with absence epilepsy. This dysfunction leads to impaired cognitive flexibility and altered cortical inhibition, linking seizure-related thalamic activity to prefrontal network imbalance. Notably, targeted stimulation of the thalamic-prefrontal pathway alleviates both seizure occurrence and cognitive deficits. These findings reveal a shared circuit mechanism underlying epileptic and cognitive symptoms, pointing to new strategies for intervention.

Cochlear implants (CIs) have successfully restored hearing in more than one million patients with severe to profound hearing loss worldwide. Although CIs effectively restore speech perception in quiet environments, sound localization remains challenging for bilateral CI users, particularly their ability to utilize interaural time differences (ITDs). The majority of clinical CI processors use a coding strategy that encodes ITD information only in the envelope of electrical pulse trains rather than their pulse timing, which may contribute to the poorer spatial hearing perception of CI users. We recently demonstrated in a behavioural study on early deafened, bilaterally CI‐implanted rats that pulse timing ITDs completely dominate ITD perception, whereas sensitivity to envelope ITDs is almost negligible in comparison. Building on this, we here investigated the neurophysiological sensitivity of the inferior colliculus (IC) to envelope and pulse timing ITDs at two different pulse rates (900 and 4500 pulses/s) and three different stimulation modulations (5, 20 and 100 Hz) in CI rats with different hearing experiences. Our results indicate that IC neurons exhibit far greater sensitivity to pulse timing ITD than envelope ITD independent of pulse rate, modulation rate or hearing experience. These findings suggest that to improve binaural hearing outcomes in bilateral CI users, clinical stimulation strategies should provide informative pulse timing ITDs. image Key points Current bilateral cochlear implants mostly provide time cues of arriving sound in the envelope of stimulation rather than in the timing of pulses. A behavioural study on cochlear implanted rats has shown that pulse timing dominates binaural hearing. Here we examined the neural sensitivity to independent changes in time cues presented on the envelope or pulse timing, respectively, in rats with bilateral cochlear implants and different hearing experiences. Auditory midbrain neurons were consistently more sensitive to changes in pulse timing rather than envelope, irrespective of stimulus pulse rate, modulation rate or an animal's hearing experience.

Magnetogenetic deep brain stimulation (MG‐DBS) represents a wireless neuromodulation that has demonstrated long‐lasting behavioral benefits in Parkinson's disease models. However, the circuit‐level mechanisms underlying these therapeutic effects have remained uncharacterized due to limitations of conventional neural interfaces. We present a bio‐integrable soft neural interface featuring ultrasoft liquid‐metal probes with bioresorbable stiffeners and customizable interconnects directly printed onto cranial surfaces to match individual skull anatomy and nanoparticle injection sites. This platform enables stable multi‐regional recordings from deep brain structures without chronic tissue damage. We systematically investigate MG‐DBS therapeutic mechanisms in a Parkinson's disease mouse model. Circuit‐level analysis reveals that MG‐DBS modulates pathological beta‐band oscillations and inter‐regional synchrony across the cortico‐basal ganglia‐thalamic circuit. Direct comparison with conventional electrical DBS demonstrates that MG‐DBS effects persisted approximately fifteen‐fold longer after stimulation cessation. Our electrophysiological recordings elucidate the mechanistic basis for this sustained therapeutic effect, providing unprecedented insights into magnetogenetic neuromodulation dynamics.

Neural interfaces for monitoring and modulating spinal nerve activity are increasingly being designed to be flexible and stretchable to enhance their biomechanical compatibility and integration. However, excessive flexibility introduces practical limitations such as difficulty in insertion into narrow spinal spaces and long-term electrical instability, hindering real-world applications. In this study, we developed a spinal nerve interface by incorporating a liquid-metal conductor and dynamic stiffness-based variable-compliance structure, which can address the challenges of current flexible neural interface technologies. During insertion, the dynamic stiffness enhancer minimizes unintended buckling and ensures minimally invasive implantation into the intended target. The proximity of the proposed device to the spinal cord increases as it flexes automatically and rapidly in a humid environment. The liquid-metal conductor maintained stable electrical properties in freely moving rats, ensuring reliable and sustained functionality. This study lays the foundation for practical, fully implantable spinal bioelectronics designed with a focus on ease of implantation and long-term functionality.

Stimulation of sensory vagal pathways is typically delivered via invasive, cervical vagus nerve stimulation (cVNS) or noninvasive, trans-auricular nerve stimulation (taNS). While both methods are investigated therapeutically, their effects on brain physiology remain poorly understood, hindering mechanistic insights and stimulus optimization. In 6 awake nonhuman primates, we recorded cortical vagal-evoked potentials (VEPs) from subdural electrodes placed in prefrontal, sensorimotor and parietal cortical areas, in response to cVNS or taNS. Across 478 different taNS and cVNS protocols, we varied stimulation side, intensity, frequency, pulse count, and pulse width and assessed independent effects on amplitude and latency of early (EC; 30-100 ms), intermediate (IC; 101-200 ms) and late components (LC; 201-500 ms) of VEPs. Fixed and random effects of stimulation parameters and subjects, respectively, on VEPs were assessed using a linear mixed-effects model. Overall, cVNS elicits more robust VEPs than taNS, with larger EC, IC and LC amplitudes, in both hemispheres. cVNS-elicited ECs and LCs are largest in PFC and PC areas, whereas ICs are largest in SM areas. On the other hand, taNS generally does not elicit area-specific responses. cVNS-elicited ECs have slower latency than ta-NS elicited ECs. Higher stimulation frequencies and intensities and a longer pulse width elicit larger ECs and ICs for cVNS, and to some extent for taNS. Both short and long cVNS trains elicit stronger ECs, and long trains elicit slower ICs. Earlobe stimulation elicits VEPs that partially overlap with those from taNS. In conclusion, cVNS and taNS elicit cortical VEPs in a manner consistent with distinct engagement of ascending vagal pathways, with both similarities and differences in the effects of stimulation parameters on evoked responses.

Norepinephrine (NE) is an important mediator of sympathetic activity that influences breathing. At the level of the inspiratory neural network, the preBötzinger complex (preBötC), NE modulation orchestrates changes in neuronal network dynamics that influence the stability of inspiratory rhythmogenesis. While this phenomenon has largely been attributed to NE-modulation of intrinsic excitability of inspiratory preBötC neurons, NE is also capable of modulating synaptic drive. Here, we resolve how NE affects synaptic properties and changes the activity dynamics of interconnected preBötC neurons in rhythmic brainstem slice preparations. Increased network burst amplitude and frequency coincided with enhanced inspiratory drive currents at the single neuron level. This increased drive was blocked by the NMDA receptor (NMDAR) antagonist, APV. Our in silico modeling indicated that synaptic calcium entry via NDMAR is key to maintaining network synchrony during this elevated state of excitability. This was consistent with our multi-electrode array studies revealing that NE-dependent NMDAR activity enhances and preserves synchrony during inspiratory network bursts. This synaptic mechanism may be a critical determinant for shaping inspiratory drive associated with changed neuromodulatory environments. Significance Statement This study demonstrates a previously undescribed synaptic mechanism by which noradrenergic modulation recruits NMDAR activity and shifts inspiratory network dynamics leading to a stable network state where synchronization is preserved among inspiratory neurons. This may be a critical mechanism preventing ventilatory instability when sympathetic activity is enhanced.

S ummary Although somatosensation is known to be important for precise hand control, how coordinated activity across sensory and motor cortical areas supports hand movements and object interactions is unclear. We simultaneously recorded neural activity from dorsal premotor cortex (PMd) and Area 2 of the primary somatosensory cortex in three rhesus macaques performing a reach-to-grasp task during recovery from a primary motor cortex (M1) lesion. Using dual-area latent factor analysis, we decomposed population activity into cross-area factors (CFs) shared between PMd and Area 2 and within-area factors (WFs) local to each region. Shared CFs tracked hand kinematics closely despite explaining less overall variance. Strikingly, the emergence of long-timescale, stereotyped sensory–motor cross-area dynamics was correlated with recovery of prehension and object grasping, whereas changes in within-area dynamics were not correlated with recovery. These findings suggest that restoration of coordinated sensory–motor population dynamics is important for recovery of skilled hand function after injury.

Theta oscillations - rhythmic patterns of synchronous activity within discrete brain regions - are known to support memory, navigation, and behavioral coordination, and are sensitive to pharmacological manipulation. Acute ethanol (EtOH) exposure has been shown to alter theta oscillations, but its effects on transient theta bursts and cross-regional coordination during naturalistic behavior remain unclear. We recorded local field potentials (LFPs) from the medial septum (MS), hippocampal Cornu Ammonis 1 (CA1), and medial prefrontal cortex (mPFC) in freely foraging mice following intraperitoneal injection of EtOH (1.5 g/kg) or saline. We analyzed spectral power, theta burst dynamics, phase, and lag timing. Burst features from CA1 were used to train a machine learning classifier to predict session condition. EtOH impaired locomotion and reduced goal-directed behaviors, particularly early in the session. In CA1, theta power shifted toward lower frequencies and lagged coherence declined. EtOH increased the frequency but reduced the duration of theta bursts in CA1, and in MS, only burst count increased. EtOH enhanced the temporal alignment of MS-CA1 burst pairs. Phase-locking between CA1 and MS during coupled bursts remained present but showed altered structure. Our classifier achieved robust performance using burst features such as skew and entropy, and reliably distinguished treatment conditions. EtOH modulates septohippocampal dynamics by altering the timing and structure of theta bursts. These results suggest that burst-level features are sensitive markers of EtOH's circuit-level effects during naturalistic behavior.

Humans and other animals can solve new problems, even on the first attempt. This capacity to generate novel problem-solving behavior has been hypothesized to depend on brain mechanisms for recombining units of knowledge using systems of procedural rules, or grammars . Yet, whether and how the brain represents and implements grammars remains unclear, in large part due to the lack of neural recordings (typically performed in animal models) during grammar-based problem solving (typically studied in humans). Here, we address that gap, and in turn identify an underlying neural basis of grammatical behavior. We designed a visual–motor construction task in which macaque monkeys trace complex, often novel, geometric figures by generating a sequence of strokes, each a distinct shape, like a circle, dash, or chevron (action symbols 1 ). Critically, sequencing was guided by a learned hierarchical action grammar A n B m C k , meaning “repeat shape A, then repeat shape B, then repeat shape C”, where the number of repetitions (n, m, and k) varied across problems. Behavior was internally generated (no cues guiding stroke order), problem-directed (to construct a specific image), and exhibited zero-shot generalization (successful on the first trial for novel problems, including harder ones)--key hallmarks of grammar use. To identify underlying neural substrates, we recorded from multiple frontal cortical areas previously implicated in rule use or action sequencing. Activity during drawing encoded key structural properties of the action grammar: (i) shape index (A, B, C), (ii) abstract role (e.g., the role A independent of the specific shape), and (iii) ordinal position within a shape repeat. Moreover, all three properties were strongest in a single region, the pre-supplementary motor area (preSMA). We suggest the possibility that this conjunction of representations is a signature of an implementation of an iterative algorithm resembling a “for-loop” program: internally tracking how many repetitions remain for each shape index and switching to the next when complete. Our study establishes a paradigm for studying the neural basis of grammar-guided novel behavior and identifies in preSMA a dynamic representation of grammatical structure supporting such behavior.

Psychedelics lead to profound changes in subjective experience and behaviour, which are typically conceptualised in psychological terms rather than corresponding to an altered brain state or a distinct state of vigilance. Here, we performed chronic electrophysiological recordings from the neocortex concomitant with pupillometry in freely moving adult male mice following an injection of a short-acting psychedelic 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT). We report an acute induction of a dissociated state, characterised by prominent slow oscillations in the cortex and marked pupil dilation in behaviourally awake, moving animals. REM sleep was initially markedly suppressed, but was overcompensated in the subsequent 48 hours, while administration of 5-MeO-DMT immediately after sleep deprivation attenuated the subsequent rebound of sleep slow-wave activity. We argue that the occurrence of a dissociated state combining features of waking and sleep may fundamentally underpin the known and hypothesised effects of psychedelics — from dream-like hallucinations to reopening of the critical period for plasticity.

Parvalbumin-expressing inhibitory neurons (PVNs) stabilize cortical network activity, generate gamma rhythms, and regulate experience-dependent plasticity. We found that PVNs act like a volume knob in the mouse auditory cortex (ACtx), bi-directionally adjusting neural and perceptual sensitivity to sound level over a 20 dB range. PVN-based gain adjustments were "sticky," such that a single bout of PVN activation at 40 Hz-but not at 1 or 70 Hz-sustainably dampened ACtx sound responsiveness, enhanced feedforward inhibition, and behaviorally desensitized mice to loudness. We then developed a mouse model of adult-onset hyperacusis by demonstrating ACtx hyperactivity, PVN hypofunction, and loudness hypersensitivity following a restricted noise-induced cochlear lesion. We found that several minutes of 40-Hz PVN stimulation in noise-exposed mice sustainably dampened ACtx hyperactivity and restored normal loudness sensitivity for 1 week. These findings demonstrate that sensory disorders caused by permanent peripheral injuries can be reversed by patterned stimulation of cortical circuits that directly regulate perception.