Publications using the Synapse

The basolateral amygdala (BLA) is important for assigning emotional weight to environmental stimuli to guide learning, discrimination, and adaptive vigilance. The contribution of neuromodulator inputs such as dopamine to this process is unclear. Here, we recorded in vivo BLA dopamine signals across emotional learning paradigms. We show that BLA dopamine scales with a stimulus's emotional intensity, but not value or associative strength, and reward-predictive cues evoke BLA dopamine signals that diminish, rather than grow, with training. In a complex learning context, where rats discriminated between multiple valenced associations, the magnitude of cue-evoked BLA dopamine re-scaled to report the level of relative emotional saliency. Threat and safety cues prompted larger, sustained dopamine signals compared to reward and neutral cues. Together, our data reveal a pattern of dopamine encoding with a unique contribution to learning, for dynamic disambiguation of affective states.

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

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

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

Social recognition, the ability to distinguish between individuals, is essential for cognitively demanding social behaviors. The anterior olfactory nucleus (AON), a primary olfactory cortical region, is implicated in this process, but the underlying neurocircuitry remains poorly understood. Here, we generated a novel mouse line to enable genetic access to AON pyramidal neurons and mapped their whole-brain synaptic inputs and outputs. The medial prefrontal cortex (mPFC), a crucial hub for social cognition, is the primary neocortical target of AON neurons, which form monosynaptic excitatory connections with a substantial fraction of mPFC neurons. The AONmPFC pathway is activated during social investigation, and chemogenetic inhibition of this pathway impairs social recognition. Moreover, an analogous AON-prefrontal pathway is present in humans, as supported by resting-state functional magnetic resonance imaging (fMRI) functional connectivity analyses. Taken together, these findings reveal a conserved olfactory-prefrontal circuit spanning mice to humans, potentially linking olfactory dysfunction to neuropsychiatric disorders.

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.

Hypothalamic AgRP neurons are uniquely responsive to nutritional cues and play an important role in fuel homeostasis. To investigate the temporal relationship between the activity of these neurons and the glycemic response to an oral glucose load, we simultaneously monitored AgRP neuron activity (by fiber photometry in AgRP-IRES-cre mice) and the arterial glucose level, both before and after oral gavage (OG) of either water or glucose (0.5-2.5 g/kg). We report that the AgRP neuron response to an OG glucose load can be subdivided into two functionally distinct phases - one that begins prior to glucose delivery and a second that extends from peak inhibition through the return towards baseline. The 'first phase' appears to be anticipatory in nature and is also predictive of subsequent changes in glycemia, suggesting a role in the handling of an oral glucose load. To analyze the relationship between the second phase response and changes of glycemia, we employed a model that allows residual activity to be removed subsequent to the 'first phase' component. This analysis reveals that unlike the first phase, the degree of residual inhibition - the second phase - tracks the glycemic response. Moreover, this response is temporally aligned with the blood glucose (BG) rate of change (which is predictive of future BG levels), with AgRP neurons lagging BG rate of change by ∼5 min. We conclude that the AgRP neuron response to an oral glucose challenge consists of two distinct phases, each with its own determinants and metabolic implications: an initial anticipatory component that is predictive of the subsequent glycemic response, and a second phase that tracks the rate of BG change.

The ventral pallidum (VP) is a key basal ganglia structure involved in integrating reward-related signals to guide motivated behavior and feeding. VP neuronal activity is strongly tuned to reward-predictive cues and palatable rewards, tracking changes in value and motivational state. Recent studies have established important and opposing roles for GABAergic and glutamatergic VP neurons in reward- and avoidance-related behaviors. However, much less is known about the role of VP cholinergic neurons (VP-CNs), which comprise only ∼10% of VP neurons in mice, but maintain extensive connectivity with reward-related circuitry. Here, using cell type-selective in vivo fiber photometry during instrumental reward behavior, we found that VP-CN activity responds to cues, actions, and reward retrieval in a training-independent manner. Phasic VP-CN responses to reward retrieval were reduced by reward dilution, whereas pre-feeding with the reward enhanced these responses. In contrast, non-cholinergic VP neurons exhibited modulation by pre-feeding but not by reward dilution. Together, these findings identify VP-CNs as a distinct and dynamically regulated VP population whose activity is sensitive to both reward palatability and physiological state, extending our current understanding of the VP and its roles in reward processing.

The medial nucleus accumbens shell (medNAcSh) is a key regulator of hedonic feeding, controlling reward consumption through its projections to downstream structures. Recent studies showed that the primary cellular mediators of these effects are dopamine 1 receptor-positive striatal projection neurons (D1-SPNs). Specifically, D1-SPN activity gets inhibited during reward consumption, and such inhibition is necessary and sufficient to authorize consumption, independent of metabolic need. Anatomically, the medNAcSh spans 1–1.5 mm along the rostro-caudal axis in mice, and previous studies have reported functional gradients along this axis. For instance, pharmacological studies have suggested that rostral rather than caudal medNAcSh regulates appetitive behavior. However, the mechanisms underlying this topographical gradient remain unknown. Here, we hypothesized that D1-SPNs contribute to this gradient by regulating hedonic feeding via a specific hotspot in the rostral medNAcSh. Using calcium monitoring with fiber photometry in mice, we show that rostral medNAcSh D1-SPNs demonstrate inhibitory responses during reward consumption, while caudal D1-SPNs do not. Consistently, optogenetic stimulation of rostral D1-SPNs inhibits consumption, while stimulation of caudal D1-SPNs had minimal effects, confirming the existence of a functional rostro-caudal gradient. Importantly, we observed no differences between rostral and caudal D1-SPNs in their responses to aversive stimuli, suggesting that the D1-SPN gradient is specific to appetitive contexts. To investigate potential molecular correlates of this functional gradient, we leveraged open-source anatomy datasets and performed fluorescent in situ hybridization, identifying Stard5 and Peg10 as markers enriched in the rostral and caudal medNAcSh, respectively. Finally, we developed a novel Stard5-Flp driver line to selectively target the rostral hotspot and demonstrated that Stard5+ neurons recapitulate rostral D1-SPN activity patterns. Together, these findings establish a spatially confined rostral medNAcSh subregion as a critical regulator of reward consumption and introduce Stard5 as a molecular tool for its manipulation, offering new opportunities for intervention in dysregulated eating.

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.

Subcortical structures like the locus coeruleus (LC) are well known to regulate pupil-linked autonomic arousal, while the role of cortical circuits in this process remains largely unclear. We designed a closed-loop optogenetic system to inactivate the anterior cingulate cortex (ACC) in real time during pupil dilations. ACC inactivation decreased the magnitude of spontaneous pupil events. In parallel, ACC population activity scaled with the magnitude of spontaneously occurring pupil dilations. In addition to modulating spontaneous arousal, ACC responses to salient sensory stimuli scaled with the size of evoked pupil dilations and ACC inactivation suppressed saliency-linked pupil events. Last, we show that LC norepinephrine neurons signal arousal faster than the ACC. However, unlike the ACC, LC responses did not scale with the magnitude of pupil dilations. Collectively, our experiments identify the ACC as a key cortical site for sustaining momentary increases in pupil-linked arousal.

Dopamine is essential for striatal function and learning. Striatal dopamine release can be triggered by dopamine cell firing, but also by coordinated cholinergic interneuron activity, which stimulates dopamine release via presynaptic nicotinic acetylcholine receptors on dopamine axons. While acetylcholine-dependent dopamine release is well-documented ex vivo and under artificial optogenetic stimulation in vivo , its role during natural behavior has remained unclear. One possible endogenous driver of acetylcholine-dependent dopamine release is thalamic input, which provides strong excitatory drive to cholinergic interneurons. To examine whether thalamic input provokes acetylcholine-dependent dopamine release during behavior, we performed simultaneous fiber photometry recordings of striatal dopamine (GRAB-rDA3m) and thalamic axon activity (gCaMP8m) in the dorsomedial (DMS) and dorsolateral striatum (DLS) of mice learning the accelerating rotarod, a striatal-dependent task that demands precise and effortful motor control. Recordings were obtained on- and off-task and across days of training to capture the full arc of learning. Dopamine transients in DMS, but not DLS, were frequently coupled to peaks in thalamic axon activity via an acetylcholine-dependent mechanism. The occurrence of these thalamic-evoked DMS dopamine transients depended on learning, task engagement, and the recent history of dopamine activity, but did not contribute to motor error signals. Together, these findings establish thalamic input as a physiological driver of acetylcholine-dependent dopamine release in DMS. Moreover, they reveal that striatal sensitivity to this local release mechanism is dynamically gated by dopaminergic history, providing a compelling framework for understanding how local and soma-triggered dopamine signals are coordinated to support learning.

Quickly adapting behavior to changing environments is key for survival. Brain dopamine signals reinforce actions that procure rewards and avoid adverse outcomes. However, the molecular mechanisms within the circuits that actuate these signals at subsecond timescales remain unexplored. We show that midbrain endocannabinoid mobilization is the conditio sine qua non for behavioral invigoration evoked by external cues. Reward- and punishment-predictive signals require intact retrograde release of the endocannabinoid 2-arachidonoylglycerol (2-AG) from ventral tegmental area dopamine neurons. Moreover, we show that genetic deletion of presynaptic cannabinoid type-1 receptors (CB1Rs), the target for 2-AG, recapitulates behavioral and dopaminergic deficits. Exploiting causal inference tools to interpret continuous brain signals, we describe that 2-AG/CB1R communication is essential for striatal dopamine release to signal salient cues and propel conditioned responding. These findings reveal an endocannabinoid-mediated disinhibition mechanism exploited by dopamine neurons to orchestrate striatal dopamine release events, enabling adaptive action selection informed by cues.

Post-stroke spasticity (PSS), characterized by hyperreflexia and spastic hypertonia, is a common and debilitating consequence of cerebrovascular injury that impedes motor recovery. Despite its prevalence, the neurophysiological mechanisms underlying PSS remain poorly understood, partly due to the lack of reliable animal models. A known clinical correlate of spasticity is weakened rate-dependent depression (RDD) of the Hoffman reflex (H-reflex), particularly in the upper limbs of chronic stroke patients. However, the mechanistic basis of RDD impairment and its relationship to brain lesion characteristics remain unclear. Here, we characterized the longitudinal progression of H-reflex RDD in a wrist flexor muscle following photothrombotic stroke in mice and examined its association with lesion volume across cortical and subcortical regions using magnetic resonance imaging. RDD was significantly reduced 2-3 weeks after stroke, indicating hyperreflexia. Approximately 60% of stroke mice exhibited weakened RDD. Notably, lesion volumes in contralateral primary (M1) and secondary (M2) motor cortices correlated positively with RDD impairment, linking greater cortical damage to more severe reflex hyperexcitability. These results suggest that damage to motor cortical regions disrupts central reflex-modulating pathways, contributing to post-stroke hyperreflexia. The presented stroke model provides a valuable platform for mechanistic investigations of PSS and for evaluating potential therapeutic interventions.

Internal states including stress and satiety, affect cue-induced feeding behaviors, yet the underlying neural mechanisms remain poorly understood. The nucleus of the solitary tract (NTS), a key hindbrain hub that integrates interoceptive and viscerosensory signals and projects to reward processing nuclei, is anatomically well-positioned to modulate cue-induced feeding behaviors in response to internal state changes. Using behavioral paradigms combined with chemogenetics and fibre photometry, this study investigated the hypothesis that NTS mediates the effects of stress and satiety on cue-induced feeding behaviors via A2 neurons and modulation of ventral tegmental area (VTA) dopamine signaling. We first showed that both foot shock stress and outcome specific satiety (i.e., sucrose prefeed) reduced cue-induced appetitive behavior. Inhibition of NTS neurons only attenuated the suppressive effect of foot shock stress, but not that of outcome specific satiety, indicating that NTS is required for stress-induced suppression of cue-induced appetitive behavior. Further investigation into the contributing neural phenotype revealed that stimulation of NTS A2 neurons reduced conditioned approach and suppressed cue-evoked VTA dopamine neural activity, without any effects on lateral hypothalamus (LH) neuron activity. Together, these findings suggest that NTS neurons mediate the effects of foot shock stress, but not outcome specific satiety, on cue-induced appetitive behavior, in part through activation of NTS A2 neurons and modulation of cue-evoked VTA dopamine neural activity. These results provide an NTS-mediated mechanism through which stress suppresses cue-induced feeding behavior.

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.

The psychedelic psilocybin has shown therapeutic potential, yet underlying neural mechanisms remain poorly understood. We investigated the impact of psilocin-the active metabolite of psilocybin-on basal activity and reactivity within the paraventricular nucleus of the thalamus (PVT) and PVT projections to central amygdala (CeA) in rats. Psilocin administration increased PVT c-Fos expression and selectively engaged PVT→CeA neurons in females, but not males. Psilocin enhanced PVT reactivity to an aversive air-puff stimulus, with effects primarily driven by passive responders. In PVT→CeA neurons, psilocin prevented time-dependent reductions in stimulus-evoked activity and maintained reactivity across timepoints in females but not males. The sustained engagement of PVT→CeA circuitry was driven by active responders. These findings identify sex-specific modulation of thalamic-limbic circuitry and behavior by psilocin, implicating PVT→CeA circuitry in the neural and behavioral effects of psychedelic compounds, advancing our understanding of how psychedelics modulate emotional brain circuits to further inform potential therapeutic mechanisms.

Non-rapid eye movement (NREM) sleep is not uniform but characterized by brief intrusions of wake-like brain activity and increased muscle tonus known as micro-arousals or brief awakenings. Although micro-arousals are an inherent feature of human and animal sleep, knowledge about the neural correlates of micro-arousals is sparse. We here developed an algorithm for automatic detection of micro-arousals based on EMG activity and used it to analyse the associated laminar neural activity in the motor cortex in mice. Our analysis showed that short micro-arousals with a duration below 5 s were associated with decreased cortical firing, while longer micro-arousals with a duration of 5–10 s were associated with increased firing in a similar manner to transitions to wakefulness. Analysis of single-channel firing showed that some channels exhibited increased activity immediately prior to micro-arousals, while others exhibited decreased activity. Slow wave activity (SWA, 1–4 Hz) immediately after micro-arousals was tightly correlated with sleep pressure and even surpassed average SWA levels during NREM sleep in sleep deprived animals. This study provides new insights into the neural mechanisms associated with micro-arousals and identifies a new link between sleep architecture and sleep homeostasis.