Electrophysiology publications

Hearing relies upon speedy synaptic transmission of sound information from inner hair cells (IHCs) to spiral ganglion neurons. To accomplish this, IHCs use a sophisticated presynaptic machinery including the multi-C 2 domain protein otoferlin that is affected by human deafness mutations. Otoferlin is essential for IHC exocytosis, but how it binds Ca 2+ and the target membrane to serve synaptic vesicle (SV) tethering, docking, and fusion remained unclear. Here, we obtained cryo–electron microscopy structures of otoferlin and employed molecular dynamics simulations of membrane binding. We show that membrane binding by otoferlin involves C 2 B-C 2 G domains and repositions C 2 F and C 2 G domains. Disruption of Ca 2+ -binding sites of the C 2 D domain in mice altered synaptic sound encoding and eliminated the Ca 2+ cooperativity of IHC exocytosis, indicating that it requires the binding of several Ca 2+ -ions by otoferlin. Together, our findings elucidate molecular mechanisms underlying otoferlin-mediated SV docking and support the role of otoferlin as Ca 2+ sensor of SV fusion in IHCs.

Human decision-making involves model-free and model-based reinforcement learning (RL) strategies, largely implemented by prefrontal-striatal circuits. Combining human brain imaging with neural network modelling in a probabilistic reversal learning task, we identify a unique role for the mediodorsal thalamus (MD) in arbitrating between RL strategies. While both dorsal PFC and the striatum support rule switching, the former does so when subjects predominantly adopt model-based strategy, and the latter model-free. The lateral and medial subdivisions of MD likewise engage these modes, each with distinct PFC connectivity. Notably, prefrontal transthalamic processing increases during the shift from stable rule use to model-based updating, with model-free updates at intermediate levels. Our CogLinks model shows that model-free strategies emerge when prefrontal-thalamic mechanisms for context inference fail, resulting in a slower overwriting of prefrontal strategy representations - a phenomenon we empirically validate with fMRI decoding analysis. These findings reveal how prefrontal transthalamic pathways implement flexible RL-based cognition.

Neuronal synchronization refers to the temporal coordination of activity across populations of neurons, a process that underlies coherent information processing, supports the encoding of diverse sensory stimuli, and facilitates adaptive behavior in dynamic environments. Previous studies of synchronization have predominantly emphasized rate coding and pairwise interactions between neurons, which have provided valuable insights into emergent network phenomena but remain insufficient for capturing the full complexity of temporal dynamics in spike trains, particularly the interspike interval. To address this limitation, we performed in vivo neural ensemble recording in the primary olfactory center—the antennal lobe (AL) of the hawk moth Manduca sexta —by stimulating with floral odor blends and systematically varying the concentration of an individual odorant within one of the mixtures. We then applied machine learning methods integrating modern attention mechanisms and generative normalizing flows, enabling the extraction of semi-interpretable attention weights that characterize dynamic neuronal interactions. These learned weights not only recapitulated the established principles of neuronal synchronization but also facilitated the functional classification of two major cell types in the antennal lobe (AL) [local interneurons (LNs) and projection neurons (PNs)]. Furthermore, by experimentally manipulating the excitation/inhibition balance within the circuit, our approach revealed the relationships between synchronization strength and odorant composition, providing new insight into the principles by which olfactory networks encode and integrate complex sensory inputs.

Parkinson’s disease (PD) has been associated with alterations in neuronal activity in the basal ganglia-thalamocortical (BGTC) network. Previous studies have suggested that cortical disinhibition is a feature of PD, but there has been little direct evidence of the changes in cortical neuronal spiking activity to support this hypothesis. To test the hypothesis that activity in the motor cortex is enhanced in PD, we investigated the effects of parkinsonism on movement-related neuronal activity in the primary motor cortex (M1). Microelectrode arrays were chronically implanted in M1 of two nonhuman primates and populations of cells were collected before and after the induction of parkinsonism using the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. In both animals, we found that during the reaching task in the parkinsonian state, the proportion of M1 neurons that were activated (excited) during movement were increased, while those that were suppressed (inhibited) decreased. These data support the concept that dopaminergic loss in parkinsonism promotes a loss of inhibition in the motor cortex, leading to overactivity in M1 and a disruption in spatial-temporal processing of information within the BGTC circuit that contributes to the motor dysfunction observed in PD.

Fragile X Syndrome (FXS) is a leading genetic cause of intellectual disability and autism-like behaviors. Glutamatergic mGluR5 receptors and matrix metalloproteinase-9 (MMP-9) are therapeutic targets to treat FXS, but clinical trials targeting each of these pathways have not been successful. Here, we tested if the electroencephalography (EEG) phenotypes associated with FXS are reversed with a novel combination of treatments affecting the two pathways. Fmr1 knockout (KO) mice were given 10 days of CTEP (mGluR5 antagonist) alone or in combination with minocycline (MMP-9 inhibitor). EEG was recorded during resting (no acoustic stimulation) and during sound presentations (to produce sound-evoked EEG) at 1 day and 10 days after the beginning of treatment administration to test acute effects and potential tachyphylaxis. In pre-treatment WT and KO mice comparisons, we replicated previously published Fmr1 KO mouse EEG phenotypes including elevated power in the resting gamma band, elevated single trial power, and reduced phase-locking to spectrotemporally dynamic auditory stimuli. We found that CTEP treatment alone did not show any benefit compared to vehicle in Fmr1 KO mice after either 1 or 10 days of treatment. CTEP + minocycline reduced resting gamma band power in the Fmr1 KO mice to a greater extent than vehicle at both treatment time points. There were no effects on sound-evoked responses. These data suggest that combined CTEP and minocycline treatment alters resting EEG measures while each treatment administered separately does not yield similar changes. High power in broadband gamma frequency correlates with irritability, stereotyped behaviors, and hyperactivity in FXS patients, suggesting a combination of drugs that reduce mGluR5 and MMP-9 activity may be beneficial in FXS.

Adolescence is a developmental period characterized by heightened plasticity. Yet, how ongoing development affects sensory processing and cognitive function is unclear. We investigated how adolescent (postnatal day 20–42) and adult (postnatal day 60–82) mice differ in performance on a pure tone Go/No-Go auditory discrimination task of varying difficulty. Using dense electrophysiological recordings, we measured spiking activity at single neuron resolution in the auditory cortex while mice were engaged in the task. As compared to adults, adolescent mice showed lower auditory discrimination performance in a difficult task. This difference in performance was due to higher response variability and weaker cognitive control expressed as higher lick bias. Adolescent and adult neuronal responses differed only slightly in representations of pure tones when measured outside the context of learning and the task. However, cortical representations after learning within the context of the task were markedly different. We found differences in stimulus- and choice-related activity at the single neuron level representations, as well as lower population-level decoding of the difficult task in adolescents. Overall, cortical decoding in adolescents was lower and slower, especially for difficult sound discrimination, reflecting immature cortical representations of sounds and choices. Notably, we found age-related differences, which were more pronounced after learning, reflecting the combined impact of age and learning. Our findings highlight distinct neurophysiological and behavioral profiles in adolescence, underscoring the ongoing development of cognitive control mechanisms and cortical plasticity during this sensitive developmental period.

The pre‐hearing mouse cochlea undergoes critical periods of spontaneous Ca 2+ ‐dependent activity that spreads across non‐sensory supporting cells and inner hair cells (IHCs). These signals have been shown to regulate not only the refinement of neural circuits along the auditory pathway towards functional maturity, but also the maturation of the hair cells into sensory receptors. Although the origin and interplay of these Ca 2+ signals during cochlear development have recently been investigated in live mice, the impact of anaesthesia on in vivo functional measurements was not explored. Here, we investigate the effects of different anaesthetic regimes (ketamine and xylazine; 2.5% isoflurane; and 1.0%–1.5% isoflurane with the sedative acepromazine) that provided an effective unconsciousness to perform the surgery and Ca 2+ ‐imaging recordings from the intact cochlea of live mice. The IHCs, supporting cells and spiral ganglion neuron terminals onto the IHCs showed spontaneous Ca 2+ ‐dependent activity under all anaesthetic regimes, with a few significant differences observed between conditions. Calcium waves from supporting cells synchronized the activity of IHCs. Moreover, we found that the endocochlear potential, which is crucial for cochlear function, was unaffected by the different anaesthetics. However, low concentrations of isoflurane produced the most stable recordings of vital physiological signs in mice, including heart rate and breathing rate. Although all anaesthetic regimes tested appeared to be suitable for performing Ca 2+ imaging from the cochlea of pre‐hearing live mice, a low concentration of isoflurane (1.0%–1.5%), combined with the pre‐anaesthetic sedative acepromazine and oxygenation, represents the most suitable approach to maintain a stable and long‐lasting depth of anaesthesia.

Hydrogels have emerged as promising materials for anti‐fibrotic neural interfaces due to their mechanical and chemical similarity to biological tissue. However, their use in multimodal platforms remains limited, owing to fabrication challenges in microstructuring multiple functional hydrogels into compact architectures. Here, a hydrogel thermal drawing process (HG‐TDP) is presented that enables the co‐fabrication of multiple thermoplastically deformable hydrogels into a single, compact, and multifunctional fiber. By optimizing key process parameters, all‐hydrogel neural interfaces are developed that minimize gliosis through tissue‐like mechanical compliance and enable post‐implantation anti‐inflammatory drug delivery via the hydrogel‐based matrix. These fibers feature the compact integration of diverse hydrogel components, including a step‐index optical waveguide, an electrically conductive hydrogel electrode, and a hydrogel‐based microfluidic channel within a unified fiber structure. This integration enables multimodal neural interfacing, as demonstrated by high‐quality neural signal recording, optogenetic stimulation, and localized chemical modulation of neural circuits. This work offers a scalable route toward compact, fully hydrogel‐based neural interfaces that combine multimodal functionality with tissue‐friendly, anti‐fibrotic properties.

Long-term sustained pain following acute physical injury is a prominent feature of chronic pain conditions1. Populations of neurons that rapidly respond to noxious stimuli or tissue damage have been identified in the spinal cord and several nuclei in the brain2-4. Understanding the central mechanisms that signal ongoing sustained pain, including after tissue healing, remains a challenge5. Here we use spatial transcriptomics, neural manipulations, activity recordings and computational modelling to demonstrate that activity in an ensemble of anatomically and molecularly diverse parabrachial neurons that express the neuropeptide Y (NPY) receptor Y1 (Y1R neurons) is increased following injury and predicts functional coping behaviour. Hunger, thirst or predator cues suppressed sustained pain, regardless of the injury type, by inhibiting parabrachial Y1R neurons via the release of NPY. Together, our results demonstrate an endogenous analgesic hub at pain-responsive parabrachial Y1R neurons.

The ability to pick out and attend to one sound in a noisy mixture underpins successful communication in many natural scenarios. Selective attention has been shown to drastically alter sound encoding in the cortex and has been hypothesized to modulate subcortical processing via an extensive efferent network. The body of work investigating this possibility in humans has not resulted in a clear consensus, possibly owing to limitations in the available methodologies. Here, we used new experimental tools that allowed distinct neural responses from across the auditory pathway to be simultaneously acquired from human listeners attending to the sound of one person talking while ignoring a second. Our series of experiments provide convergent evidence that selective attention does not influence sound encoding in the auditory periphery or brainstem, with an effect first appearing in the cortex. Humans’ ability to focus their attention on a single sound even in the presence of many others is as remarkable as it is essential. These findings add needed clarity regarding the mechanisms that make this feat possible.

Cerebral cortex and cerebellum are essential for sensorimotor control, but the dynamics of their interactions remain unclear. Here, we investigated which pathways prevail during preparation and execution of spontaneous whisker movements in mice. During preparation, neuronal activity of primary motor (M1) and somatosensory (S1) cortex precede that of cerebellar crus regions, with a lead that is consistent with relaying a copy of motor commands. After movement onset, the phase of the signal inverts, indicating a dominant vector signaling from cerebellum to cerebrum. At this stage, Purkinje cell activity correlates more with S1 than M1, generating a prediction of sensory consequences during motor actions. A computational cerebello-cortical model could replicate the changes in dynamics and directionality. Optogenetic manipulations of pons and thalamus confirm the modeled predictions on stage-dependent dynamics. Together our data point towards a swap in direction of information flow between cerebrum and cerebellum when motor preparation switches to execution.

Background: Chronic pain affects approximately 20% of the population, with a higher prevalence in females, and presents significant diagnostic and treatment challenges. While opioids are commonly prescribed, they carry risks of addiction and overdose, highlighting the need for reliable pain biomarkers. New Method: To develop such a biomarker, we recorded non-noxious and noxious evoked potentials from the primary somatosensory cortex (S1) in 8 female pigs across 16 sessions. A convolutional neural network (CNN) was trained, validated, and tested on time-frequency maps of these responses. Three interpretability methods, saliency, integrated gradients, and occlusion were applied to identify neural features critical for distinguishing pain states. Results: The CNN achieved an overall accuracy of 73.5%, with higher accuracy for non-noxious stimuli (85%) than for noxious stimuli (62%). Feature attributions consistently highlighted a window 93–173 ms post-stimulus in the 35–75 Hz gamma-band. Comparison with Existing Methods: The CNN automatically extracted features from spectrograms, addressing the overlap between noxious and non-noxious responses. Interpretability methods revealed gamma-band oscillations (GBOs) consistent with nociceptive processing in humans and rodents. While this architecture offers valuable insights, recent studies suggest that hybrid models (e.g., CNN-LSTM) and transformers may further improve performance and robustness. Conclusion: This CNN-based approach identified GBOs as a promising neural marker of pain, with potential applications in translational research, pre-clinical trials, and pain assessment in non-verbal subjects.

Classical neuromodulators regulate arousal states, spanning deep sleep to vigilant wakefulness, primarily by activating cortical neurons. However, cortical astrocytes also express neuromodulatory G-protein-coupled receptors (GPCRs). While astrocytic noradrenergic receptors have been shown to modulate two critical regulators of arousal—cortical synchrony and extracellular adenosine levels—how other neuromodulatory signaling pathways similarly shape arousal remains unclear. Astrocytes in mammalian cortex express particularly high levels of the wake-promoting, Gq-coupled histamine-1-receptor (H1R), yet little is known about how astrocytic H1R contributes to regulation of arousal. To address this gap, we used pharmacological and genetic approaches in murine cortex to test how astrocyte-H1R signaling affects astrocyte calcium (Ca 2+ ), cortical neural activity across sleep/wake, and extracellular adenosine—an astrocytic output that regulates cortical arousal. Using ex vivo two-photon Ca 2+ imaging in acute cortical slices, we show that H1R mediates cell-autonomous astrocyte Ca 2+ responses to histamine (HA) and attenuates responses to norepinephrine (NE). Next, in vivo fiber photometry and electrophysiology results show that H1R deletion in cortical astrocytes disrupts local astrocyte Ca 2+ during wake and extracellular adenosine dynamics specifically around REM sleep transitions, when HA release is minimal. Further, astrocyte-specific H1R deletion in cortex promotes wakefulness and reduces REM sleep time. Our results indicate that H1R activity modulates astrocyte responses to non-histaminergic inputs by inducing lasting changes in astrocyte physiology that modulate extracellular adenosine and REM sleep. Our findings contribute to an emerging model in which neuromodulator GPCRs synergistically shape astrocyte physiology to regulate arousal behavior and adenosine signaling in the cortex.

Absence epilepsy is frequently associated with cognitive impairments, yet the direct or indirect involvement of cognitive circuits remains poorly understood, as spike-and-wave discharges are rarely reported in these regions. Here, we investigate the role of a thalamic–prefrontal pathway in a mouse model of absence epilepsy (Scn8a +/- ). We find that Scn8a +/- mice exhibit deficits in reversal learning, along with impaired recruitment of medial prefrontal cortex (mPFC) neurons by the Reuniens nucleus of the thalamus. This deficit is accompanied by an altered excitation–inhibition balance and reduced excitability of layer I interneurons in the mPFC, which constitutes the main recipient zone of reuniens inputs to the mPFC. Remarkably, stimulation of Reuniens at 20 Hz significantly reduces seizure incidence and improves performance in reversal learning. Our findings reveal previously unrecognized cognitive circuit dysfunctions in absence epilepsy and highlight the thalamo–prefrontal axis as a promising target for both cognitive and seizure-related interventions.

Sympathetic hyperactivity is a common feature observed in both primary and secondary hypertension, and neuromodulation-based therapies targeting this overactivity are under active investigation. The intermediolateral nucleus (IML) in the spinal cord plays a central role in sympathetic regulation, and its direct stimulation induces a transient, frequency-dependent reduction in blood pressure. However, this effect gradually diminishes as the baroreflex restores blood pressure to baseline. Therefore, this study aims to develop a closed-loop (CL) stimulation system that adjusts parameters in real-time based on neural activity recorded from the IML and to enhance and prolong the transient antihypertensive effect. This strategy was evaluated in normotensive and angiotensin II-induced hypertensive rat models and compared to open-loop (OL) stimulation of equal intensity. In both models, CL stimulation produced a more sustained blood pressure reduction than that of OL stimulation. These findings suggest that CL spinal cord stimulation offers a more effective and durable therapeutic option for treating hypertension.

Cross-modal responses are common in primary sensory cortex, yet a recent study showed that signals in primary visual cortex (V1) once labeled multisensory were instead more closely related to face movements. To what extent can multisensory processing in other modalities also be explained by face movements? We measured face movements and neural activity in awake mouse primary auditory cortex (A1) and V1 in response to visual and auditory stimulation as well as during spontaneous activity. We find that visual stimuli rarely evoke face movements, A1 responses to visual input remain robust even in the absence of face movement, and optogenetic silencing of V1 reduces A1 visual responses. Taken together, these results confirm that cross-modal responses in the auditory system are primarily sensory, not state driven, in origin.

Basolateral amygdala (BLA) GABAergic interneurons (INs) are critical for associative learning; however, the comparative synaptic organization and learning-related activity of BLA IN types have not been systematically evaluated. Here, we show somatostatin (SOM) INs provide inhibition onto, and are excited by, local pyramidal cells (PCs), whereas vasoactive intestinal peptide (VIP) INs are driven by extrinsic afferents. Parvalbumin (PV) INs inhibit PCs and are activated by local and extrinsic inputs. Thus, SOM and VIP INs exhibit complementary roles in feedback and feedforward inhibition, respectively, while PV INs contribute to both microcircuit motifs. Functionally, each IN subtype exhibits unique activity patterns across fear and extinction learning, with SOM and VIP INs showing most divergent characteristics, and PV INs display an intermediate phenotype. Finally, SOM and PV INs dynamically track behavioral-state transitions across learning. These data provide insight into the synaptic microcircuit organization and activity of distinct BLA IN classes across aversive associative learning.

Most spinal cord injuries (SCI) spare descending and sublesional circuits that can be targeted through motor cortex and spinal cord stimulation to mitigate locomotor deficits. However, the potential synergy between cortical and spinal stimulation remains unknown. Here, we first investigated the phase-locked electrical stimulation of the motor cortex and lumbar spinal cord at 40 Hz in a rat model of unilateral SCI. Combining cortical and lumbar stimulation around the anticipated lift synergistically enhanced leg movements. When integrated into rehabilitation training, cortical stimulation proved essential for the recovery of skilled locomotion. We next investigated the effects of high-frequency (330 Hz) lumbar and sacral stimulation combined with cortical stimulation. Timely integration during the swing phase showed that cortical and lumbar stimulations enhance the initial and mid-swing phases, while sacral stimulation improves extension velocity in the late swing. These findings indicate that supraspinal and sublesional neuromodulation offer complementary neuroprosthetic effects in targeted SCI gait rehabilitation.

Humans live in an environment that contains rich auditory stimuli, which must be processed efficiently. The entrainment of neural oscillations to acoustic inputs may support the processing of simple and complex sounds. However, the characteristics of this entrainment process have been shown to be inconsistent across species and experimental paradigms. It is imperative to establish whether neural activity in response to speech is a result of combination of simple evoked responses or of entrainment of neural oscillations in human participants. In this study, 12 participants with intracranial electrodes listened to natural speech and neural entrainment as evidenced by oscillatory activity persisting beyond the evoked responses was assessed. Neural activity was recorded from 165 contacts in Heschl's gyrus and superior temporal gyrus. First, acoustic edges in the speech envelope induced coherence between speech and auditory cortex activity. Further, entrainment in the theta-alpha band outlasted the acoustic stimulation. This activity exceeded what could be expected from a simple evoked response. These findings suggest that speech has the potential to entrain neural oscillations in the human auditory cortex.

Mounting evidence suggests that elevated beta oscillatory activity in the basal ganglia thalamocortical (BGTC) network is associated with the cardinal motor signs in people with Parkinson's disease (PD). The evolution of abnormal beta oscillatory activity across the BGTC network as motor signs emerge, however, is not well understood. The goal of this study was to investigate whether beta oscillatory activity in the BGTC network changes prior to and how it evolves during the emergence of mild parkinsonian motor signs. To address this question, we performed simultaneous neural recordings in the subthalamic nucleus (STN), the internal and external globus pallidus (GPi and GPe), motor thalamus (Th), and the primary motor cortex (M1) in a progressive, non-human primate (NHP) model of PD using sequential injections of low-dose 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The emergence of mild PD motor signs was associated with an increase in STN, GPi, GPe, and Th beta power in both subjects. Although changes in cortical beta power were noted in both subjects before the emergence of motor signs, the direction of change differed between subjects. Our data provide compelling evidence that changes in beta oscillatory activity occur early and are found across the BGTC network during the initial expression of parkinsonian motor signs. These findings support the hypothesis that abnormal beta oscillatory activity in the BGTC network plays a significant role in the neural pathogenesis that underlies the development of PD motor signs.