The Journal of Neuroscience

When we produce sounds ourselves, the brain modulates the auditory neural response through an efference copy mechanism, allowing us to distinguish between self-initiated and externally generated auditory inputs. However, the precise level of the auditory pathway at which this attenuation occurs remains unclear. While evidence from animal models suggests that early auditory processing of self-generated sounds may be modulated by corticofugal signaling, localized cortical modulation would preserve the high-fidelity subcortical sound encoding while allowing flexible, context-dependent processing at higher levels. To probe potential motor influences in the early auditory system, we collected scalp-recorded frequency following responses (FFRs) from 33 normal-hearing adults during active (self-initiated) and passive (externally presented) listening conditions using a 170 ms speech stimulus. Data were collected with a vertical montage that emphasizes subcortical generators of the FFR. We observed no significant differences in the FFR between active and passive conditions in spectral power, response amplitude, pitch tracking, onset latency, or phase consistency. In contrast, cortical event-related potentials showed motor-induced suppression (MIS): reduced early peak amplitudes in the active condition after correcting for motor signals, increased phase consistency prior to auditory feedback, and more precise phase consistency at sound offset. In addition to indicating FFRs can be collected during a wider range of behavioral tasks without substantial motor contamination, our observation of the canonical MIS in cortical signals but not in FFRs suggests that MIS of self-initiated sounds primarily affects later stages of auditory processing rather than the early encoding reflected in the FFR.

The paraventricular nucleus of the thalamus (PVT) has emerged as an important node in circuits regulating motivated behavior. The neuronal pathway from the lateral hypothalamus (LH) to the PVT has specifically been shown to regulate arousal, feeding, and reward seeking. However, the involvement of the LH-PVT pathway in individual differences in cue-motivated behavior remains unclear. During a Pavlovian conditioned approach paradigm, when a reward is repeatedly preceded by the presentation of a cue, rats come to exhibit a conditioned response to the cue. One extreme of the population, sign-trackers (STs), approach and interact with the cue itself; while the other extreme, goal-trackers (GTs), approach the location of reward delivery. Intermediate responders (IRs) approach and interact with both the cue and reward location, without a clear preference. We utilized a Pavlovian conditioned approach paradigm to examine the effects of LH-PVT pathway inhibition on individual differences in cue-motivated behavior. A dual-vector approach was used to selectively express inhibitory chemogenetic receptors in the LH-PVT pathway. We found that inhibition of the LH-PVT pathway selectively attenuates the expression of goal-tracking behavior, without affecting sign-tracking. This effect is driven primarily by IR rats, as inhibition of LH-PVT neurons attenuates goal-tracking behavior in IRs, without impacting the response of STs or GTs. We speculate that the flexibility of responding in IR rats made them especially vulnerable to this manipulation. These findings identify the LH-PVT pathway as a selective contributor to reward-directed conditioned responding and a circuit substrate for behavioral flexibility. Significance StatementIndividuals differ in how reward-predictive cues motivate behavior, a feature linked to vulnerability and resilience to maladaptive reward seeking. The paraventricular thalamus (PVT), a midline hub with broad limbic connectivity, and its input from the lateral hypothalamus (LH) influences arousal, feeding, and reward seeking, but the role of the LH-PVT pathway in individual variability in cue-motivated behavior is unclear. We used chemogenetics to selectively suppress LH-PVT neurons during a Pavlovian conditioned approach paradigm. Inhibiting this projection reduced goal-tracking without altering sign-tracking, and this effect was driven primarily by intermediate responders, a phenotype characterized by behavioral flexibility. These results implicate LH-PVT signaling in reward-directed conditioned responding and suggest that this pathway contributes to flexible cue-motivated behavior.

Memory formation relies on the hippocampus and unfolds over time across experience, such as during the visual exploration of complex, naturalistic scenes. Eye movements evoke hippocampal activity, including fixation-locked field potentials and phase resets of theta oscillations. This suggests that hippocampal encoding is temporally structured by the sequence of visual fixations. Because eye-movement sequences sample semantically meaningful portions of scenes, they provide temporal structure to semantic content in memory. However, it remains unclear how the semantic content and temporal order of fixations jointly shape medial temporal lobe activity. We therefore tested whether intracranial EEG recordings from human hippocampus and amygdala reflect the semantic content and temporal order of individual fixations during encoding of naturalistic scenes. Relative to other semantic content, fixations on people were particularly relevant for memory, with the first fixation on a person predicting subsequent scene recognition. Fixation-locked hippocampal responses were enhanced for fixations to people relative to other semantic content, expressed in both larger fixation-evoked potentials and stronger theta phase locking. These effects were strongest for the first fixation relative to subsequent fixations. Theta phase locking was also enhanced in both hippocampus and amygdala for first fixations on people relative to later fixations and to other semantic content. These findings indicate that medial temporal lobe activity is structured by discrete fixation-level events during scene encoding, suggesting that theta-paced sampling contributes to the transformation of semantic and temporal components of visual experiences into memory. Significance StatementThis study shows that the semantic content and order of eye fixations jointly influence human hippocampal activity during memory encoding. Combining intracranial recordings, eye-movement tracking, and deconvolutional modeling, we show that the first glance at a person within naturalistic scenes is a privileged event, associated with increased hippocampal activity, theta-phase resetting in hippocampus and amygdala, and subsequent memory success. These findings recast eye movements not as mere motor acts, but as an important process that helps medial-temporal structures prioritize and integrate behaviorally relevant information into episodic memory.

Reaching and grasping are essential goal-directed behaviors that require the integration of visual, olfactory, and somatosensory inputs. Although the loss of vision can profoundly disrupt sensory-guided behaviors, mammals often exhibit compensatory cross-modal plasticity allowing them to reach and grasp with ease. To examine how early sensory loss shapes reaching behavior, we performed bilateral enucleations in short-tailed opossums (Monodelphis domestica) at postnatal day 4, before retino-thalamic and thalamocortical connections have formed. We assessed performance in early blind (EB) and sighted control (SC) animals using a semi-naturalistic reach-to-grasp task requiring precise unilateral limb targeting to retrieve a dead cricket. To isolate the contributions of specific sensory modalities to this task, we selectively disrupted olfactory and mystacial vibrissae inputs and manipulated lighting conditions during task performance. EB opossums were capable of accurate reaching and grasping, although SC animals outperformed EB opossums under light conditions, but not in the absence of light. Both groups relied strongly on tactile input, as whisker trimming significantly increased targeting error. Removal of olfactory input also impaired performance, with a disproportionately greater effect in EB animals. These findings demonstrate that short-tailed opossums retain functional reach-to-grasp behavior after early vision loss and that accurate forelimb movements are generated by the enhancement of the spared sensory systems. Significance StatementCongenital sensory loss in humans alters the landscape used to navigate the world, making compensatory strategies mediated by the spared sensory systems essential for goal-directed behaviors such as reaching and grasping. Although these behaviors have been widely studied across species, the extent to which spared senses support their execution after congenital vision loss remains unclear. Here, we use the short-tailed opossum as a model of congenital blindness to quantify the contributions of whisker-mediated touch and olfaction to reaching performance. We show that both early blind and sighted opossums rely on whisker touch for reaching and grasping, but that olfaction plays a profound role in task performance in early blind opossums.

Optogenetic stimulation of the rostral pedunculotegmental nucleus (PTg) induces global motor arrest, but it remains unclear whether this is merely a suppression of motor activity or a broader disruption of brain processes required to guide action. We developed a visuospatial cue task for rats, to test if sensory information presented during PTg-induced arrest can guide later responses. Here, we show that optogenetic stimulation during cue presentation reduces accuracy to chance level. By moving stimulation to only before or only after the cue, we found that performance was only affected when stimulation and cue presentation overlapped, that rats recover cue-guided behavior almost immediately at the end of stimulation, and that stimulation does not appear to abolish responses based on cue information acquired before arrest. These findings indicate that stimulation of the rostral PTg does not only pause motor output but transiently disrupts the ability to process and use cue information effectively.

Coherent scenes facilitate object recognition, but the representational basis of this facilitation and its temporal evolution in the brain remain unclear. We tested this question using EEG and multivariate pattern analysis while 15 participants categorized objects from five semantic categories after a 500-ms preview of either an intact rendered scene or a phase-scrambled version of the same background. Reliable object decoding emerged earlier in intact scenes than scrambled scenes (142 {+/-} 5 vs. 162 {+/-} 10 ms), with higher decoding for intact scenes from 124 to 268 ms after object onset. Cross-condition decoding object information that generalized across scene formats, whereas subtracting cross-condition from within-condition decoding identified an earlier and stronger context-dependent component when scene structure was coherent. Cross-temporal representational similarity analysis (RSA) further showed that representational structure established during late scene preview generalized to early object processing only for intact scenes, linking contextual facilitation to anticipatory scene-derived representations. Finally, model-to-brain RSA showed that a language-aligned model explained neural representational geometry in intact scenes better than vision-only models, an advantage attenuated by scene scrambling. These findings indicate that coherent scene context shapes object coding by accelerating object-selective processing and contributing context-dependent representational structure beyond a context-invariant object code.

The medial prefrontal cortex (mPFC) plays a significant role in modulating the threat response, particularly in ambiguous circumstances. The mPFC performs this role through its connectivity with multiple brain regions, including the amygdala, long regarded as the central hub for threat responses. However, the roles of specific prefrontal projections to the amygdala in contextual threat discrimination are not yet fully understood, particularly regarding more complex learning tasks and when disentangling the functionally distinct prelimbic (PL) subunit of the mPFC. Here, we challenged mice with a contextual differential threat conditioning (DTC) learning task in which subjects were repeatedly exposed to one context predictive of a foot shock (CS+) and to a similar yet distinct context that was not (CS-). While control mice showed a similar threat response in both contexts immediately after threat conditioning, within a few days of contextual exposures, controls acquire threat discrimination and freeze less to CS- than to CS+ during late DTC. However, we found that inducing localized hypofunction of neuroplasticity in PL neurons projecting to the basolateral amygdala (BLA) impairs performance on DTC. This finding identifies the specific population of neurons in PL cortices as a critical site for learning to discriminate threat.

Membrane protein trafficking is essential for synaptic growth, maintenance, function, and plasticity, and involves the regulated exocytosis and endocytosis of proteins to and from the pre-and post-synaptic membranes. Defects in the clearance of membrane proteins can lead to the accumulation of ubiquitinated membrane proteins and contribute to neurodegenerative disease. The ESCRT (endosomal sorting complexes required for transport) machinery binds and sorts ubiquitinated membrane proteins into lysosomes for degradation, yet the presence and function of ESCRTs in sorting ubiquitinated AMPA and other receptors at the post-synapse remain unclear. Here we show that the ubiquitin-binding ESCRT-0 protein, Hrs, localizes to both pre- and post-synapses, and levels are modulated by neuronal activity, increasing and decreasing with higher and lower neuronal activity, respectively. Phosphoproteomic profiling of Hrs-depleted post-synaptic membranes revealed a role for Hrs in glutamatergic synaptic transmission, including long-term potentiation. In addition, Hrs-depleted neurons showed faster AMPAR current kinetics and reduced amplitude in whole-cell patch-clamp recordings. Genetic deletion of neuronal Hgs in mice led to reductions in phosphorylated CaMKII- and -{beta} (T286/T287) and structural proteins, PSD-95 and gephyrin, suggestive of LTD (long-term depression)-like synaptic depression. In contrast, Hrs overexpression led to increases in Ca2+-dependent signaling, including protein kinase C (PKC) and PKC substrate, AMPAR subunit GluA1-S831, a site which increases conductance. Together, these findings identify a dynamic, bidirectional role for Hrs at the post-synapse as it both senses and is modulated by neuronal activity, ultimately impacting excitatory synaptic strength. Significance StatementSynaptic plasticity relies on dynamic trafficking and turnover of membrane proteins, including AMPA-type glutamate receptors (AMPARs), yet how receptor trafficking intersects with ubiquitin-mediated sorting pathways at synapses remains unclear. We show that the ubiquitin-binding ESCRT-0 protein, Hrs, localizes to both pre- and post-synapses, and its abundance is bidirectionally regulated by neuronal activity. Genetic depletion of Hrs in mice reduces CaMKII phosphorylation and impacts AMPAR channel surface localization. In contrast, neuronal-specific Hrs overexpression led to enhanced GluA1 and protein kinase C substrate phosphorylation, suggesting altered AMPAR trafficking, subunit composition, and/or function. Thus, Hrs emerges as a modulator of glutamatergic signaling, coupling ubiquitin-mediated receptor sorting to the fine-tuning of synaptic transmission, with direct implications for learning and memory in health and disease.

The hippocampal CA3 subfield is central to associative learning and memory consolidation. The principal cells of the CA3, pyramidal neurons, execute these functions by generating hypersynchronous bursts that feed forward to the CA1. Extensive recurrent collateral connections within the CA3 neuron population are crucial for the generation of this burst activity. Double C2 domain-containing protein (Doc2) and synaptotagmin 7 (Syt7) are high-affinity calcium sensors implicated in asynchronous synaptic vesicle (SV) release and in the exocytosis of dense-core vesicles (DCVs). Additionally, Doc2 is a sensor for miniature neurotransmission, whereas Syt7 is involved in synaptic facilitation and SV replenishment. Both Doc2 and Syt7 are expressed in the hippocampus, but their potential roles in spontaneous excitatory network activity remain unanswered. Using whole-cell recordings in disinhibited acute hippocampal slices obtained from juvenile Doc2- and Syt7- knockout (KO) mice (P15-21), we report increased CA3 burst generation without changes in spontaneous excitatory postsynaptic current (sEPSC) frequency or amplitude. Moreover, the intrinsic properties of CA3 pyramidal neurons, such as the resting membrane potential, firing rate and input resistance, are unchanged. We propose that this novel burst phenotype in Doc2- and Syt7- KO mice is unrelated to changes in SV release but might be mediated by changes in neuropeptide release from DCVs. Regardless of the underlying mechanisms, this work reveals that both proteins act to regulate network activity. The hippocampal CA3 subfield is central to associative learning and memory consolidation. The principal cells of the CA3, pyramidal neurons, execute these functions by generating hypersynchronous bursts that feed forward to the CA1. Extensive recurrent collateral connections within the CA3 neuron population are crucial for the generation of this burst activity. Double C2 domain-containing protein (Doc2) and synaptotagmin 7 (Syt7) are high-affinity calcium sensors implicated in asynchronous synaptic vesicle (SV) release and in the exocytosis of dense-core vesicles (DCVs). Additionally, Doc2 is a sensor for miniature neurotransmission, whereas Syt7 is involved in synaptic facilitation and SV replenishment. Both Doc2 and Syt7 are expressed in the hippocampus, but their potential roles in spontaneous excitatory network activity remain unanswered. Using whole-cell recordings in disinhibited acute hippocampal slices obtained from juvenile Doc2- and Syt7- knockout (KO) mice (P15-21), we report increased CA3 burst generation without changes in spontaneous excitatory postsynaptic current (sEPSC) frequency or amplitude. Moreover, the intrinsic properties of CA3 pyramidal neurons, such as the resting membrane potential, firing rate and input resistance, are unchanged. We propose that this novel burst phenotype in Doc2- and Syt7- KO mice is unrelated to changes in SV release but might be mediated by changes in neuropeptide release from DCVs. Regardless of the underlying mechanisms, this work reveals that both proteins act to regulate network activity.

The auditory brain excels at extracting predictive regularities from sound, but the neural and temporal mechanisms mediating long-term learning of these regularities remain poorly understood. Here, using a perceptual anchoring paradigm, we investigate whether the dorsolateral prefrontal cortex (dlPFC) is causally required to transform transient regularities into stable internal templates (anchors). We characterized the behavioural dynamics of anchoring to predicable acoustic events using sensitivity (d) and decision bias (c) metrics, alongside growth curve analysis (GCA) to model trial-by-trial learning. Listeners exhibited a robust anchoring effect, showing significantly higher sensitivity in decision strategy for recurring acoustic regularities compared to novel ones. This implicit anchoring was driven selectively by specific features in regular sequences--the local repetition of an acoustic motif--whereas explicit memory indiscriminately encoded the entire acoustic episode. To test for causality, we applied inhibitory continuous theta-burst stimulation (cTBS) to the dlPFC. Crucially, not only did this not impair anchoring, but significantly accelerated the rate of anchoring for predictable patterns, suggesting the dlPFC may act as a source of top-down interference in implicit learning. In contrast to predictable sequences, inhibition of dlPFC disrupted the initial precision of online comparisons for novel sequences, though insulating against the rapid, interference-driven reduction in performance or novel sequences in observed in listeners subjected to a sham cTBS procedure. These findings reveal a functional dissociation. Whilst dlPFC provides an essential buffer for novel sensory comparisons, long-term consolidation of regularities in acoustic sequences relies on a robust implicit pathway independent of prefrontal control.

Hypothalamic A11 dopamine neurons provide the only known source of spinal dopamine and critically modulate pain and motor systems. Yet, the electrophysiological properties of A11 neurons were unknown. Here, we characterized A11 dopamine neurons in mice using brain slice immunohistochemistry, and fluorescence-guided whole-cell patch-clamp and cell-attached electrophysiology. A11 dopamine neurons contained the enzymes necessary to synthesize dopamine, projected to the spinal cord, and were small, morphologically simple, and high resistance. Additionally, they received excitatory glutamatergic and inhibitory GABAergic synaptic input. Most A11 dopamine neurons fired action potentials spontaneously in a rhythmic pacemaker manner at [~]5 Hz, while the remainder were quiescent at rest, but fired readily with somatic current injection. Pacemaking A11 dopamine neurons were differentiated from quiescent neurons by a net inward current at subthreshold potentials. Activation of mu-opioid receptors reduced the net inward current at subthreshold potentials via activation of potassium current but also decreased GABAergic synaptic currents onto A11 dopamine neurons. Using cell-attached recording to preserve the natural chloride gradient, we found mu-opioid receptor agonism reduced spontaneous action potential firing of A11 dopamine neurons. The results lay the necessary framework for future studies investigating synaptic and ion channel mechanisms underlying the excitability in A11 dopamine neurons in physiological and pathological conditions.

The medial prefrontal cortex (mPFC) and its connections with the posterior dorsomedial striatum are implicated in goal-directed learning, but the specific mPFC cell types involved have not been clearly established. The current study investigated mPFC intratelencephalic (IT) and pyramidal tract (PT) neuron involvement in goal-directed learning. In Cre-driver mouse lines, we mapped bilaterally projecting IT neurons and unilaterally projecting PT neurons from mPFC to dorsal striatum and showed that chemogenetic inhibition of IT, but not PT neurons, attenuated goal-directed learning. We then demonstrated training induced elevations in pERK signaling in IT neurons, which were transient in superficial mPFC layers, and more persistent in deeper layers. This was associated with plasticity in deep layer IT neurons, reflected in a shift towards excitatory over inhibitory synaptic inputs. Together, these data suggest that goal-directed learning influences synaptic input and downstream plasticity markers in mPFC IT neurons, and this functionally contributes to goal-directed learning.

Adaptive avoidance depends on a delicate balance: animals must act rapidly when a cue predicts danger, but suppress the same action when the cue no longer has consequence. How MCH neuromodulatory signaling shapes this prefrontal updating process remains poorly understood. Here, we identify melanin-concentrating hormone receptor 1 (MCHR1) signaling as a regulator of active avoidance extinction. Pharmacological MCHR1 antagonism with SNAP-94847 left acquisition of two-way active avoidance intact, but promoted extinction once the tone was no longer followed by shock. This effect was reproduced by prelimbic mPFC-targeted SNAP infusion, indicating that prefrontal MCHR1 signaling contributes to the persistence of learned avoidance. Fiber photometry from CaMKII-positive mPFC neurons revealed that MCHR1 antagonism enhanced excitatory prefrontal activity during successful avoidance and altered trial-history-dependent mPFC activity during extinction, most prominently on avoidance trials that followed previous avoidance. These findings identify MCHR1 signaling as a regulator of adaptive avoidance updating and suggest that MCHR1 antagonism facilitates extinction by altering prefrontal processing of recent action history when a formerly protective response loses behavioral value. Significance StatementIn anxiety- and trauma-related disorders, avoidance can persist long after danger is gone, interfering with daily life. While avoidance is essential for survival, it can become harmful when it is no longer needed. We found that blocking brain receptors for melanin-concentrating hormone helps mice stop responding to outdated warning signals while preserving their ability to learn from danger. We identify the medial prefrontal cortex as a key brain region where this intervention changes activity during fear-guided behavior. This study highlights a potential therapeutic strategy for reducing excessive avoidance without compromising normal protective responses.

T-stellate neurons in the ventral cochlear nucleus (VCN) receive synaptic input from the cochlear nerve and encode information about sound frequency and intensity, including rapid fluctuations in sound intensity that are important for speech processing. T-stellate neurons are the only neuron class in the VCN that projects directly to the inferior colliculus (IC), the midbrain hub of auditory processing. However, which IC neuron populations receive T-stellate input and how T-stellate input influences IC neuron excitability remain unknown. Using channelrhodopsin-assisted circuit mapping and whole-cell patch clamp recordings in brain slices, we compared the synaptic strength, prevalence, and short-term synaptic plasticity of T-stellate input to two molecularly defined classes of IC neurons: GABAergic neuropeptide Y (NPY) neurons and glutamatergic vasoactive intestinal peptide (VIP) neurons. Our results revealed that T-stellate neurons provide excitatory input to both NPY and VIP neurons, with T-stellate input to NPY neurons having a higher incident rate, larger magnitude, and faster kinetics than T-stellate input to VIP neurons. In many instances, T-stellate input also recruited feedforward inhibition and feedforward excitation onto NPY and VIP neurons. In addition, T-stellate input to NPY and VIP neurons exhibited short-term synaptic depression that became larger in amplitude at higher stimulation frequencies. These data provide insights on how T-stellate neurons influence individual neuron types and local circuits in the IC, laying a mechanistic foundation for investigating how T-stellate input contributes to frequency tuning, amplitude modulation selectivity, and speech processing in the IC.

Neuronal activity drives long-lasting change in circuit function by inducing the expression of gene products that modulate the function of synapses. Arc is one of the most robustly activity-regulated neuronal genes, being induced broadly in neurons by a wide range of physiologically-relevant stimuli. The ability of Arc to promote internalization of AMPA-type glutamate receptors plays an important role in activity-dependent refinement of synaptic connectivity during development. However, the consequences of Arc induction for circuit plasticity in the adult brain are less well understood. We reasoned that we could test the requirement for experience-induced Arc expression in downstream plasticities by disrupting regulatory elements that mediate the inducibility of Arc transcription. To achieve this goal, we developed and validated a CRISPR-based inhibition strategy to conditionally block stimulus-induced expression of Arc in specific regions of the brains of male and female adult mice in vivo. We show that recruiting transgenic dCas9-KRAB to decrease transcriptional activity of either the promoter or the synaptic activity-regulated enhancer of the Arc gene is sufficient to block Arc protein expression in visual cortex (V1) following light exposure or in the nucleus accumbens (NAc) following cocaine administration. However, loss of Arc in V1 failed to alter plasticity of orientation selectivity and loss of Arc in NAc did not block cocaine conditioned place preference or novel object recognition memory. These data show that the relationship between Arc induction and plasticity is not universal and suggest that additional contextual factors determine the functional consequences of Arc induction for plasticity. Significance StatementArc is a neuronal activity-regulated gene whose expression is robustly induced in the adult brain by a wide range of stimuli that drive plasticity. However, the functional requirements of Arc induction for brain plasticity are incompletely understood. Here, we show that we can use transgenic mice expressing the CRISPR-based transcriptional repressor dCas9-KRAB to block stimulus-induced expression of Arc in specific regions of the adult mouse brain. Despite highly effective inhibition of Arc induction, we found that many forms of plasticity remained intact. These data deepen understanding of the contextual importance of activity-induced Arc expression in the adult brain.

Human functional magnetic resonance imaging studies of fear conditioning often average neural responses across trials, potentially obscuring transient activations that vary across learning. In this study with 139 participants, we examined finer temporal dynamics of conditioned responding by analyzing three 2s segments within the conditioned stimulus (CS) presentation period across each quarter of fear acquisition and extinction training. This approach revealed distinct, time-specific engagement of regions within fear- and safety-related networks, both within and across trials. In particular, different activation patterns emerged across the three trial segments during CS presentation, indicating that neural responses were not limited to CS onset. We observed a more classical activation pattern at 0s relative to CS onset that diverged in later trial segments, most notably involving the amygdala, hippocampus, and prefrontal cortex (PFC) structures such as vmPFC present exclusively in 2s and 4s trial segments. We also found sustained activations consistent across all blocks of trials, such as right vlPFC activation 4s after CS onset across all fear acquisition quarters. These findings suggest that conditioned fear and safety processing unfold as dynamic spatiotemporal cascades and highlight the importance of modeling later responses following CS onset rather than focusing exclusively on onset-related activation.

Epileptic encephalopathies (EEs) are severe developmental disorders with abnormal EEG activity that worsens neurodevelopmental deficits, yet underlying sensory and cognitive impairment mechanisms are unclear. We studied cortical circuit dynamics in Ank3-1b-/- mice, an EE model with parvalbumin interneuron dysfunction, using laminar electrophysiology, spike-field coherence (SFC), single-unit analyses, and behavioral assays. Ank3-1b-/- mice showed disrupted excitatory-inhibitory (E-I) balance, with reduced sink/source ratios (p = 0.0279) and elevated net currents (AVREC; p < 0.01), indicating hyperexcitability. In awake states, sensory-evoked intra-columnar connectivity was impaired, with lower Pearson correlations (p < 0.001) and increased low-frequency (3-30 Hz) SFC (p < 0.001), but intact gamma-band coherence, suggesting aberrant synchronization. Inhibitory neuron latencies were delayed in infragranular layers under anesthesia (p < 0.001) and supragranular layers when awake (p = 0.005), implying thalamocortical deficits. Despite preserved sensory adaptation and recognition memory, Ank3-1b-/- mice exhibited heightened anxiety (p < 0.05) and variable circadian rhythms, indicating selective affective and regulatory deficits. These results show that Ank3-1b loss disrupts cortical E-I balance and synchrony, delaying sensory processing, while compensatory mechanisms maintain critical sensory functions. This study links ANK3 mutations to layer-specific circuit dysfunction, offering insights into EE pathophysiology and sensory deficits.

Attention is a fundamental mechanism enabling the brain to overcome its limited capacity for parallel processing. In non-human primates, invasive electrophysiology has shown that attentional selection operates rhythmically, primarily within the alpha ([~]8-12 Hz) and theta ([~]4-5 Hz) bands. Whether such finely resolved control signals can be captured non-invasively in humans, and how they adapt to changing task demands, remains unclear. Using high-precision magnetoencephalography (MEG) combined with machine learning, we decoded the spatial locus of covert attention in humans performing three variants of a spatial cueing task that manipulated cue validity as well invalid trial switching rules. Spatial attention could be decoded from whole-brain MEG activity at both static and time-resolved scales, with accuracies significantly above chance (N = 30). Decoding performance decreased as cue validity was reduced, indicating that task structure shapes attentional engagement. Analysis of decoding trajectories revealed rhythmic fluctuations at [~]8-12 Hz across all tasks, demonstrating alpha-band sampling of attention. Pre-target attention became increasingly focused on the cued side, especially in the 100% Valid condition, consistent with proactive orienting. Furthermore, individual and task-specific differences in decoding strength correlated with task-variations in behavioral performance, linking the accuracy of neural attention codes to both discrimination accuracy and reaction time. These findings demonstrate that MEG can non-invasively capture dynamic, task-dependent fluctuations in spatial attention that parallel those observed in non-human primates. They reveal that attentional demands reshape the neural code for attention, modulate rhythmic sampling, and influence behavioral efficiency. This work bridges invasive primate and non-invasive human research and establishes MEG-based decoding of attention as a promising tool for mechanistic and clinical applications, including neurofeedback and attention-related interventions.

The circadian system is an important regulator of reward-related neural function and behavior. Dopamine (DA) release in the nucleus accumbens is a key component of reward processing, yet how circadian timing shapes DA release in relation to reward behavior remains unclear. Here, we investigated circadian rhythms in DA release and reward behavior using long-term fiber photometry paired with an automated reward delivery and measurement system. We found two distinct circadian rhythms in DA release: spontaneous DA, reflecting ongoing DA release not associated with reward, and reward-evoked DA, reflecting transient DA response during reward. Spontaneous DA peaked during the early subjective day, whereas reward-evoked peak DA peaked near the day-to-night transition. Both rhythms were distinct from reward behavior, which peaked during the early subjective night. Linear modeling further showed that the relationship between reward-evoked DA and reward behavior depended on circadian time, with greater DA responses occurring between late subjective day and early subjective night. Spontaneous baseline and reward-evoked DA were also negatively correlated, and this relationship was likewise modulated across circadian time. Together, these findings support a model in which circadian modulation of baseline DA may alter the gain of reward-evoked signaling, amplifying DA responses across behaviorally relevant times of day.

P/Q-type calcium channel (Cav2.1) is the major channel that mediates Ca2+ influx during action potentials (APs) and evokes neurotransmitter release from presynaptic terminals. Repetitive activity induces its Ca2+-dependent facilitation (CDF) via binding of calmodulin (CaM) superfamily proteins to the IQ-like motif, specifically isoleucine (I) and methionine (M) sites, on the cytoplasmic c-terminus of Cav2.1. However, whether and how CDF contributes to short-term synaptic plasticity remains elusive. By recordings from the calyx of Held terminal in IQ-like motif point mutation knock-in mice (Cav2.1 IM-AA KI), we found that activity-dependent CDF is completely abolished, resulting in lower quantal output and shorter release time course as well as profound reductions in the magnitute of short-term facilitation and depression (STF and STD) in different Ca2+ concentrations. Prolonging deactivation of Ca2+ channels by broadening spike width normalizes quantal output and release time course in Cav2.1 IM-AA synapses, but does not fully rescue STF/STD. These results indicate that CDF of Cav2.1 channels governs the polarity and magnitude of short-term synaptic plasticity in fast-spiking central synapses.