Synchronous neuronal ensembles play a pivotal role in the consolidation of long-term memory in the hippocampus. However, their organization during the acquisition of spatial memory remains less clear. In this study, we used neuronal population voltage imaging to investigate the synchronization patterns of mice CA1 pyramidal neuronal ensembles during the exploration of a new environment, a critical phase for spatial memory acquisition. We found synchronous ensembles comprising approximately 40% of CA1 pyramidal neurons, firing simultaneously in brief windows (~25ms) during immobility and locomotion in novel exploration. Notably, these synchronous ensembles were not associated with contralateral ripple oscillations but were instead phase-locked to theta waves recorded in the contralateral CA1 region. Moreover, the subthreshold membrane potentials of neurons exhibited coherent intracellular theta oscillations with a depolarizing peak at the moment of synchrony. Among newly formed place cells, pairs with more robust synchronization during locomotion displayed more distinct place-specific activities. These findings underscore the role of synchronous ensembles in coordinating place cells of different place fields.

Foraging and food consumption are fundamental for the survival of animals. In natural environments, wild rodents feed on insects, including moth larvae, and odor-guided evaluation of potential food resources is a critical step in initiating feeding behavior. However, the mechanisms by which rodents seek and feed on insect prey remain poorly understood. Herein, we employed a laboratory-based predator-prey interaction system using mice and cotton bollworm larvae to investigate the neural mechanisms underlying food-seeking and feeding behaviors at both cellular and neural circuit levels. We demonstrate that mice exhibit a strong preference for consuming fed larvae, and this preference is dependent on the main olfactory system. Gas chromatography-mass spectrometry analysis revealed significant differences in the chemical profiles of fed and unfed larvae, with fed larvae containing a higher level of linoleic acid (LA) and a lower level of (Z)-9-tricosene [(Z)-9-TE]. Behavioral assays showed that mice, as well as Brand's voles and brown rats, are attracted to LA but avoid (Z)-9-TE in a two-choice odor preference test. Furthermore, we identified that the dopaminergic pathway from the ventral tegmental area (VTA) to the medial olfactory tubercle (mOT) plays a central role in mediating this preference. Chemogenetic inhibition of this pathway abolished the preference for LA over (Z)-9-TE, while chemogenetic activation reversed this effect. Additionally, fiber photometry recordings and pharmacology revealed that mOT D1 and D2 spiny projection neurons preferentially mediate attraction to LA and avoidance of (Z)-9-TE, respectively. These findings uncover a neurobiological system in rodents that supports insect predation based upon chemosignals.

Sleep entails profound changes in the brain and body, marked by altered states of consciousness and reduced somatic and autonomic motor activity. Regarding "how" sleep is regulated, whole-brain screening revealed large sleep-control networks spanning the forebrain, midbrain, and hindbrain. We unify diverse experimental evidence under a "motor theory," in which the sleep-control mechanism is integral to somatic and autonomic motor circuits. Regarding the "why" question, sleep deprivation impairs cognition, emotion, metabolism, and immunity. We propose catecholamine (dopamine, noradrenaline, and adrenaline) inactivation as the fundamental biological process underlying sleep's numerous benefits. Beyond brain arousal and motor activity, catecholamines regulate metabolism and immunity; their sleep-dependent suppression yields wide-ranging advantages, promoting repair and rejuvenation. Furthermore, catecholaminergic neurons are metabolically vulnerable; their need for rest and recovery may drive homeostatic sleep pressure. Together, the motor theory offers a unifying framework for sleep control, while the catecholamine hypothesis posits a core mechanism mediating sleep's multifaceted benefits.

This review examines the cholinergic (Ch) basal forebrain and its role in neurodegeneration. Terminology used to describe Ch cells and the complex region of the basal forebrain are reviewed. Practical autopsy sampling and labeling strategies for Ch cells are discussed and illustrated with the goal of facilitating diagnostic work and autopsy-based studies of this region. The anatomic connectivity of the system is reviewed with an emphasis placed on the dense cholinergic input to the amygdala, the major target of the Ch basal forebrain, as well as the hippocampus. Ch and basal forebrain neuropathology in various neurodegenerative diseases is then briefly discussed, including more recent studies of TDP-43 proteinopathies. Finally, areas for further study that might further the understanding of the Ch system in neurodegeneration are emphasized.

Social learning enables a subject to make decisions by observing the actions of another. How neural circuits acquire relevant information during observation to guide subsequent behavior is unknown. Utilizing an observational spatial working memory task, we show that neurons in the rat anterior cingulate cortex (ACC) associated with spatial trajectories during self-running in a maze are reactivated when observing another rat running the same maze. The observation-induced ACC activities are reduced in error trials and are correlated with activities of hippocampal place cells representing the same trajectories. The ACC activities during observation also predict subsequent hippocampal place cell activities during sharp-wave ripples and spatial contents of hippocampal replay prior to self-running. The results support that ACC neurons involved in decisions during self-running are reactivated during observation and interact with hippocampal replay to guide subsequent spatial navigation.

Hippocampal remapping, in which place cells form distinct activity maps across different environments, is a well-established phenomenon with a range of theoretical interpretations. Some theories propose that remapping helps to minimize interference between competing spatial memories, whereas others link it to shifts in an underlying latent state representation. However, how these interpretations of remapping relate to one another, and what types of activity changes they are compatible with, remains unclear. To unify and elucidate the mechanisms behind remapping, we here adopt a neural coding and population geometry perspective. Assuming that hippocampal population activity can be understood through a linearly-decodable latent space, we show that there are three possible mechanisms to induce remapping: (i) a true change in the mapping between neural and latent space, (ii) modulation of activity due to non-spatial mixed selectivity of place cells, or (iii) neural variability in the null space of the latent space that reflects a redundant code. We simulate and visualize examples of these remapping types in a network model, and relate the resultant remapping behavior to various models and experimental findings in the literature. Overall, our work serves as a unifying framework with which to visualize, understand, and compare the wide array of theories and experimental observations about remapping, and may serve as a testbed for understanding neural response variability under various experimental conditions.

Dysfunction of the basal ganglia is implicated in a wide range of neurological and psychiatric disorders. Our understanding of the operation of the basal ganglia is largely derived on data from studies conducted on mice, which are frequently used as model organisms for various clinical conditions. The striatum, the largest compartment of the basal ganglia, consists of 90-95% striatal projection neurons (SPNs). It is therefore crucial to establish if human and mouse SPNs have distinct or similar properties, as this has implications for the relevance of mouse models for understanding the human striatum. To address this, we compared the general organization of the somato-dendritic tree of SPNs, the dimensions of the dendrites, the density and size of spines (spine surface area), and ion channel subtypes in human and mouse SPNs. Our findings reveal that human SPNs are significantly larger, but otherwise the organisation of the dendritic tree (dendrogram) with an average of approximately 5 primary dendrites, is similar in both species. Additionally in both humans and mice, over 90% of the spines are located on the terminal branches of each dendrite. Human spines are somewhat larger (4.3 versus 3.1 μm2) and the terminal dendrites have a uniform diameter in both humans and mice, although somewhat broader in the latter (1.0 versus 0.6 μm). The composition of ion channels is also largely conserved. These data have been used to simulate human SPNs building on our previous detailed simulation of mouse SPNs. We conclude that the human SPNs essentially appear as enlarged versions of the mouse SPNs. This similarity suggests that both species process information in a comparable manner, supporting the relevance of mouse models for studying the human striatum.

Compulsive actions are typically thought to reflect the dominance of habits over goal-directed action. To investigate this, we mimicked the striatal neuroinflammation that is frequently exhibited in individuals with compulsive disorders in rats, by injecting the endotoxin lipopolysaccharide into the posterior dorsomedial striatum, and assessed the consequences for behavioural control. Surprisingly, this manipulation caused rats to acquire and maintain goal-directed actions under conditions that would otherwise produce habits. Immunohistochemical analyses indicated that these behaviours were a result of astrocytic proliferation. To probe this further, we chemogenetically activated the Gi-pathway in striatal astrocytes, which altered the firing properties of nearby medium spiny neurons and modulated goal-directed action control. Together, results show that striatal neuroinflammation is sufficient to bias action selection toward excessive goal-directed control via dysregulated astrocyte function. If translatable, our findings suggest that, contrary to conventional views, individuals with striatal neuroinflammation might be more prone to maladaptive goal-directed actions than habits, and future interventions should aim to restore appropriate action control.

The striatum plays a central role in action selection and reinforcement learning, integrating cortical inputs with dopaminergic signals encoding reward prediction errors. While dopamine modulates synaptic plasticity underlying value learning, the mechanisms that enable selective reinforcement of behaviorally relevant stimulus-action associations-the structural credit assignment problem-remain poorly understood, especially in environments with multiple competing stimuli and actions. Here, we present a computational model in which acetylcholine (ACh), released by striatal cholinergic interneurons, acts as a channel-specific gating signal that restricts plasticity to brief temporal windows following action execution. The model implements a biologically plausible three-factor learning rule requiring presynaptic activity, postsynaptic depolarization, and phasic dopamine, with plasticity gated by cholinergic pauses that temporally align with behaviorally relevant events. This mechanism ensures that only synapses involved in the selected behavior are eligible for modification. Through systematic evaluation across tasks with distractors and contingency reversals, we show that ACh-gated learning promotes synaptic specificity, suppresses cross-channel interference, and yields increasingly competitive performance relative to Q-learning in complex tasks, reflecting the scalability of the proposed learning mechanism. Moreover, the model reveals distinct roles for striatal pathways: direct pathway (D1) neurons maintain stimulus-specific responses, while indirect pathway (D2) neurons are progressively recruited to suppress outdated associations during policy adaptation. These findings provide a mechanistic account of how coordinated cholinergic and dopaminergic signaling can support scalable and efficient reinforcement learning in the striatum, consistent with experimental observations of pathway-specific plasticity.

Measuring synaptic efficacy and defining the rules for induction of synaptic plasticity at identified connections in the mammalian brain is essential for understanding how synapses contribute to learning and memory. This requires new approaches to selectively evoke presynaptic activity and measure postsynaptic responses with high spatiotemporal resolution and high sensitivity over long periods in vivo. Here we develop an all-optical approach to probe synaptic plasticity at identified cerebellar synapses in awake, behaving mice. We developed and applied JEDI-2Psub, a genetically encoded voltage indicator with increased sensitivity around resting membrane potentials, to record subthreshold and suprathreshold activity in Purkinje cell (PC) dendrites while selectively activating their granule cell (GrC) inputs using optogenetics and their climbing fiber (CF) inputs using sensory stimulation. We measured synaptic potentials and complex spike signals across the dendrites of multiple neighboring PCs, enabling us to examine correlations in voltage signals within and between neurons. We show how pairing GrC activity with sensory-evoked CF inputs can trigger long-term plasticity of inhibitory responses in PCs. These results provide a blueprint for defining the rules for plasticity induction at identified synapses in awake animals during behavior.

Episodic memories are initially encoded in the hippocampus and subsequently undergo systems consolidation into the neocortex. The nature of memories stored in the hippocampus and neocortex differs, with the cortex encoding memories in more generalized forms. Although several brain regions encode social information, the specific cortical regions and circuits involved in the consolidation of social memories and the nature of the information encoded in the cortex remain unclear. Using in vivo Ca imaging and optogenetic manipulations, we found that infralimbic (IL) neurons projecting to the nucleus accumbens shell (IL) store consolidated social memories in male mice. Inactivating IL neurons that responded to a familiar conspecific impaired the recognition of other familiar mice including littermates, demonstrating that these neuronal activities support social familiarity. Furthermore, inactivating hippocampal ventral CA1 neurons projecting to the IL region disrupted the consolidation of memory for newly familiarized mice while sparing the recognition of littermates. These findings demonstrate the critical role of hippocampal-cortical interactions in the consolidation of social memory.

Every explored environment is represented in the hippocampus by the activity of distinct populations of pyramidal cells (PCs) that typically fire at specific locations called their place fields (PFs). New PFs are constantly born even in familiar surroundings (during representational drift), and many rapidly emerge when the animal explores a new or altered environment (during global or partial remapping). Behavioral time scale synaptic plasticity (BTSP), a plasticity mechanism based on prolonged somatic action potential (AP) bursts induced by dendritic Ca/NMDA plateau potentials, was recently proposed as the main cellular mechanism underlying new PF formations (PFFs), but it is unclear whether burst-associated large somatic [Ca] transients are always necessary and/or sufficient for PFF. To address this issue, here we performed in vivo two-photon [Ca] imaging of hippocampal CA1 PCs in head-restrained mice to investigate somatic [Ca] dynamics underlying PFFs in familiar and novel virtual environments. Our results demonstrate that although many PFs are formed by BTSP-like events, PFs also emerge with initial [Ca] dynamics that do not match any of the characteristics of BTSP. BTSP- and non-BTSP-like new PFFs occur spontaneously in familiar environments, during neuronal representational switches, and instantaneously in new environments. Our data also reveal that solitary [Ca] transients with larger amplitudes than those evoking BTSP-like PFFs frequently occur without inducing PFs, demonstrating that large [Ca] transients per se are not sufficient for PFF.

Dopaminergic neurons (DANs) in the substantia nigra pars lateralis (SNL) project to the tail of striatum, where they contribute to threat behaviors. Auditory cortex contributes to threat conditioning, but whether it directly modulates DANs is unclear. Here, we show that SNL DANs fire irregularly, achieve rapid maximal firing rates, exhibit distinct ionic conductances, and receive predominantly excitatory input. This contrasts with substantia nigra pars compacta (SNc) DANs that fire regularly and receive mainly inhibitory input, establishing SNL DANs as a physiologically distinct dopaminergic subpopulation. Functional mapping revealed robust excitatory input from auditory and temporal association cortices to SNL DANs, but not SNc DANs. In behavioral experiments, inhibiting neurotransmitter release from either SNL DANs or cortical afferents to SNL resulted in impaired auditory threat conditioning. Thus, our work reveals robust functional corticonigral projections to SNL DANs which directly regulate threat behaviors.

Dopamine midbrain (DA) neurons are involved in a wide array of key brain functions including movement control and reward-based learning. They are also critical for major brain disorders such as Parkinson Disease or schizophrenia. DA neurons projecting to distinct striatal territories are diverse with regards to their molecular makeup and cellular physiology, which are likely to contribute to the observed differences in temporal dopamine dynamics. Among these regions, the dorsolateral striatum (DLS) displays the fastest dopamine dynamics, which might control the moment-to-moment vigor and variability of voluntary movements. However, the underlying mechanisms for these DLS-specific fast DA fluctuations are unresolved. Here, we show that DLS-projecting DA neurons in the substantia nigra (SN) possess a unique biophysical profile allowing immediate 10-fold accelerations in discharge frequency via rebound bursting. By using a combination of patch-clamp recordings in projection-defined DA SN subpopulations from adult male mice and developing matching projection-specific computational models, we demonstrate that a strong interaction of Ca3 and SK channels specific for DLS-projecting Aldh1a1-positive DA SN (DLS-DA) neurons controls the gain of fast rebound bursting, while K4 and HCN channels mediate timing of rebound excitability. In addition, GIRK channels activated by D2- and GABA-receptors prevent rebound bursting in these DLS-DA neurons. Furthermore, our in vivo patch-clamp recordings and matching in vivo computational models provide evidence that these unique rebound properties might be preserved in the intact brain, where they might endow specific computational properties well suited for the generation of fast dopamine dynamics present in the dorsolateral striatum. DLS-projecting DA neurons in the SN exhibit unique rebound bursting that enables rapid, 10-fold increases in firing frequency. This firing fingerprint is driven by Ca3 and SK channel interactions, modulating burst gain, and fine-tuned by K4 and HCN channels controlling rebound timing. GIRK channels, activated by D2- and GABA-receptors, inhibit this bursting. In vivo patch-clamp recordings provide evidence that these rebound dynamics might be preserved in the intact brain, potentially supporting the fast dopamine fluctuations crucial for controlling movement vigor and variability in the DLS. These findings provide insights into the mechanisms underlying fast DA dynamics and their role in motor function, with implications for brain disorders like Parkinson disease and schizophrenia.

Similar to motor skill learning in mammals, vocal learning in songbirds requires a set of interconnected brain areas that make up an analogous basal ganglia-thalamocortical circuit known as the anterior forebrain pathway (AFP). Although neural activity in the AFP has been extensively investigated during awake singing, very little is known about its neural activity patterns during other behavioral states. Here, we used chronically implanted Neuropixels probes to investigate spontaneous neural activity in the AFP during natural sleep and awake periods in male zebra finches. We found that during sleep, neuron populations in the pallial region LMAN (lateral magnocellular nucleus of the nidopallium) spontaneously exhibited synchronized bursts that were characterized by a negative sharp deflection in the local field potential (LFP) and a transient increase in gamma power. LMAN population bursts occurred primarily during non-rapid eye movement (NREM) sleep and were highly reminiscent of sharp-wave ripple (SWR) activity observed in rodent hippocampus. We also examined the functional connectivity within the AFP by calculating the pairwise LFP coherence. As expected, delta and theta band coherence within LMAN and Area X was higher during sleep compared to awake periods. Contrary to our expectations, we did not observe strong coherence between LMAN and Area X during sleep, suggesting that the input from LMAN into Area X is spatially restricted. Overall, these results provide the first description of spontaneous neural dynamics within the AFP across behavioral states. Although cortical and basal ganglia circuits are known to be required for learning in both mammals and birds, little is known about the ongoing spontaneous activity patterns within these circuits, or how they are modulated by behavioral state. Here we prove the first description of cortical-basal ganglia network activity during sleep and awake periods in birds. Within the pallial area LMAN, we observed population-wide bursting events that were highly reminiscent of hippocampal sharp-wave ripple (SWR) activity, suggesting that large-scale population events have diverse functions across vertebrates.

Spiny projection neurons (SPNs) in the dorsal striatum play crucial roles in locomotion control and value-based decision-making. SPNs, which include both direct-pathway striatonigral and indirect-pathway striatopallidal neurons, can be further classified into subtypes based on distinct transcriptomic profiles and cell body distribution patterns. However, how these SPN subtypes regulate spontaneous locomotion in the context of environmental valence remains unclear. Using Sepw1-Cre transgenic mice, which label a specific SPN subtype characterized by a patchy distribution of cell bodies in the dorsal striatum, we found that these patchy striatonigral neurons constrain motor vigor in response to valence differentials. In a modified light/dark box test, mice exhibited differential walking speeds between the light and dark zones. Genetic ablation of these patchy SPNs disrupted restful slowing in the dark zone and increased zone discrimination by speed. In vivo recordings linked the activity of these neurons to zone occupancy, speed, and deceleration, with a specific role in mediating deceleration. Furthermore, chemogenetic activation of patchy SPNs-and optical activation of striatonigral neurons in particular-reduced locomotion and attenuated speed-based zone discrimination. These findings reveal that a subtype of patchy striatonigral neurons regulates implicit walking speed selection based on innate valence differentials.

Audiovisual working memory (WM) plays a critical role in multisensory cognitive processing, yet its structural neural correlates remain insufficiently understood. This study employed an audiovisual dual n-back task paradigm and voxel-based morphometry (VBM) to investigate gray matter volume (GMV) associations with behavioral performance in 60 healthy individuals. Behavioral results revealed a significant visual dominance effect under high cognitive load: visual performance remained stable across conditions, whereas auditory performance declined. Structural analyses showed modality-specific GMV correlations. Visual performance was positively associated with GMV in the insula, posterior cingulate, hippocampus, and inferior frontal regions, while auditory performance was negatively correlated with GMV in the angular and middle occipital gyri. Notably, the left cuneus exhibited a strong positive correlation with the Δd prime difference under high load, suggesting its potential role in cross-modal resource allocation. Furthermore, cognitive overload appeared to disrupt the structure-behavior associations observed under lower load, highlighting a load-dependent dissociation within executive control and sensory integration regions. These findings underscore the distinct anatomical substrates supporting audiovisual WM and the neural basis of visual dominance, offering structural markers for targeted cognitive training and clinical intervention.

By recording large populations of neurons in flying bats, two recent studies have observed sequential activities in the hippocampus that represent ongoing spatial trajectories during movement and recently experienced trajectories during rest, analogous to 'theta sweeps' and 'replay' previously described in rodents.

It has been shown that in the CA1 region of the hippocampus, dopamine modulates memory functions by influencing spike-timing-dependent plasticity (STDP) and intrinsic neuronal properties. Although experimental findings have suggested potential mechanisms, their detailed interplay remains incompletely understood. Here, using a realistic CA1 pyramidal neuron model, we have investigated the possible effects of dopaminergic modulation on a neuron's signal integration and synaptic plasticity processes. The results suggest a physiological plausible explanation for the puzzling experimental observation that long-term potentiation (LTP) increases in spite of a reduction in the neuron's excitability, and explains why physiological dopamine levels are necessary for LTP induction. The model suggests experimentally testable predictions on which ion channel kinetic properties can modulate the interplay between synaptic plasticity and neuronal excitability, thereby identifying potential molecular targets for therapeutic intervention.

In temporal lobe epilepsy, interictal spikes (IS) - hyper-synchronous bursts of network activity - occur at high rates in between seizures. We sought to understand the influence of IS on working memory by recording hippocampal local field potentials from male epileptic mice while they performed a delayed alternation task. Interestingly, the rate of IS during behavior did not correlate with performance. Instead, we found that IS were correlated with worse performance when they were spatially non-restricted and occurred during running. In contrast, when IS were clustered at reward locations, animals tended to perform well. A machine learning decoding approach revealed that IS at reward sites were larger than IS elsewhere on the maze, and could be classified as occurring at specific reward locations. Finally, a spiking neural network model revealed that spatially clustered IS preserved hippocampal replay, while spatially dispersed IS disrupted replay by causing over-generalization. Together, these results show that the spatial specificity of IS on the maze, but not rate, correlates with working memory deficits. In people with epilepsy, the hippocampus can generate large electrical discharges in the period between seizures called interictal spikes. Previous studies have proposed that interictal spikes cause memory impairments. We use a mouse model of epilepsy and computer simulations to study how interictal spikes impact navigation to remembered rewards. We find that when interictal spikes occur uncontrollably throughout the maze memory performance is worse, and in contrast, when they are sequestered to reward locations memory performance is better. Together our results show that interictal spikes are correlated with corrupted memory depending on when and where they occur during learning.

Disinhibitory neurons throughout the mammalian cortex are powerful enhancers of circuit excitability and plasticity. The differential expression of neuropeptide receptors in disinhibitory, inhibitory, and excitatory neurons suggests that each circuit motif may be controlled by distinct neuropeptidergic systems. Here, we reveal that a bombesin-like neuropeptide, gastrin-releasing peptide (GRP), recruits disinhibitory cortical microcircuits through selective targeting and activation of vasoactive intestinal peptide (VIP)-expressing cells. Using a genetically encoded GRP sensor, optogenetic anterograde stimulation, and trans-synaptic tracing, we reveal that GRP regulates VIP cells most likely via extrasynaptic diffusion from several local and long-range sources. In vivo photometry and CRISPR-Cas9-mediated knockout of the GRP receptor (GRPR) in auditory cortex indicate that VIP cells are strongly recruited by novel sounds and aversive shocks, and GRP-GRPR signaling enhances auditory fear memories. Our data establish peptidergic recruitment of selective disinhibitory cortical microcircuits as a mechanism to regulate fear memories.

Volumetric functional imaging of transient cellular signaling and motion dynamics is often limited by hardware bandwidth and the scarcity of photons under short exposures. To overcome these challenges, we introduce squeezed light field microscopy (SLIM), a computational imaging approach that rapidly captures high-resolution three-dimensional light signals using only a single, low-format camera sensor. SLIM records over 1,000 volumes per second across a 550-µm diameter field of view and 300-µm depth, achieving 3.6-µm lateral and 6-µm axial resolution. Here we demonstrate its utility in blood cell velocimetry within the embryonic zebrafish brain and in freely moving tails undergoing high-frequency swings. Millisecond-scale temporal resolution further enables precise voltage imaging of neural membrane potentials in the leech ganglion and hippocampus of behaving mice. Together, these results establish SLIM as a versatile and robust tool for high-speed volumetric microscopy across diverse biological systems.

In vivo voltage imaging is a powerful tool for monitoring action potentials and dynamic electrical events in heterogeneous sensory neurons enabling the deciphering of rapid somatosensory information processing. Virus-driven expression of genetically encoded voltage indicator (GEVI) suffers from inconsistent expression levels and offers a limited time window for optimal voltage imaging. Here, we generated and characterized a knock-in mouse line with Pirt-driven expression of Marina, a positively tuned GEVI, in primary sensory neurons. Pirt-Marina mice enable optical reporting of touch, itch, and nociceptive sensations in vivo and distinct action potential patterns in the trigeminal and dorsal root ganglion neurons. Notably, Pirt-Marina mice display robust fluorescence signals in response to mechanical, thermal, or chemical stimuli, allowing visualization of transformations in sensory coding following inflammation and injury. This Pirt-Marina mouse line provides optical access to dynamic neuronal activity and plasticity in the peripheral nervous system (PNS) with high temporal accuracy, fidelity, and reliability.

A long-standing question in biology and medicine concerns how astrocytes influence neurons. Here, progress concerning how astrocytes affect neurons and neural circuits is summarized by focusing on data and concepts from studies of the striatum, which has emerged as a model nucleus. Mechanisms broadly applicable across brain regions and disorders are emphasized, and knowledge gaps are described. Experiments spanning multiple scales of biology show that astrocytes regulate neural circuits by virtue of homeostatic signaling and through astrocyte-neuron interactions. During disease, astrocytes contribute to nervous system malfunction in context-specific ways through failures of normal functions and the development of maladaptive responses. As ideally positioned endogenous cellular neuromodulators, astrocytes can be targeted for strategies to regulate neural circuits in brain disorders. After a historically slow start for the field, astrocyte-neuron interactions are now recognized as consequential for physiology and behavior, critically involved in pathophysiology, and exploitable in disease.

Every explored environment is represented in the hippocampus by the activity of distinct populations of pyramidal cells (PCs) that typically fire at specific locations called their place fields (PFs). New PFs are constantly born even in familiar surroundings (during representational drift), and many rapidly emerge when the animal explores a new or altered environment (during global or partial remapping). Behavioral time scale synaptic plasticity (BTSP), a plasticity mechanism based on prolonged somatic action potential (AP) bursts induced by dendritic Ca2+/NMDA plateau potentials, was recently proposed as the main cellular mechanism underlying new PF formations (PFF), but it is unclear whether burst-associated large somatic [Ca2+] transients are always necessary and/or sufficient for PFF. To address this issue, here we performed in vivo two-photon [Ca2+] imaging of hippocampal CA1 PCs in head-restrained mice to investigate somatic [Ca2+] dynamics underlying PFFs in familiar and novel virtual environments. Our results demonstrate that although many PFs are formed by BTSP-like events, PFs also emerge with initial [Ca2+] dynamics that do not match any of the characteristics of BTSP. BTSP and non-BTSP-like new PFFs occur spontaneously in familiar environments, during neuronal representational switches and instantaneously in new environments. Our data also reveal that solitary [Ca2+] transients with larger amplitudes than those evoking BTSP-like PFFs, frequently occur without inducing PFs, demonstrating that large [Ca2+] transients per se are not sufficient for PFF.

In the hippocampal formation, cholinergic modulation from the medial septum/diagonal band of Broca (MSDB) is known to correlate with the speed of an animal's movements at sub-second timescales and also supports spatial memory formation. Yet, the extent to which sub-second cholinergic dynamics, if at all, align with transient behavioral and cognitive states supporting the encoding of novel spatial information remains unknown. In this study, we used fiber photometry to record the temporal dynamics in the population activity of septo-hippocampal cholinergic neurons at sub-second resolution during a hippocampus-dependent object location memory task using ChAT-Cre mice of both sexes. Using a linear mixed-effects model, we quantified the extent to which cholinergic dynamics were explained by changes in movement speed, behavioral states such as locomotion, grooming, and rearing, and hippocampus-dependent cognitive states such as recognizing a novel location of a familiar object. The data show that cholinergic dynamics contain a multiplexed code of fast and slow signals i) coding for the logarithm of movement speed at sub-second timescales, ii) providing a phasic spatial novelty signal during the brief periods of exploring a novel object location, and iii) coding for recency of environmental change at a seconds-long timescale. Furthermore, behavioral event-related phasic cholinergic activity demonstrates that fast cholinergic transients correlate with a switch in cognitive and behavioral states. These findings enhance understanding of the mechanisms by which cholinergic modulation contributes to the coding of movement speed and encoding of novel spatial information. Acetylcholine is well known as a neuromodulator of cognitive functions and behavior, and computational models suggest an important role in the encoding of new memories. However, whether cholinergic dynamics are fast enough to serve as a spatial novelty signal is unknown. Here, we demonstrate that cholinergic signaling in the septo-hippocampal circuitry of mice exhibits multiple timescales of activity, where fast signals reflect the detection of novel object locations, encode the logarithm of movement speed, and correlate with behavioral state transitions. At longer timescales, cholinergic transients encode recency of environmental change. These findings provide important insights into the mechanisms by which acetylcholine contributes to encoding and retrieval dynamics and the acquisition of spatial memories during exploratory behavior and memory-guided navigation.

Traditional views of hippocampal function are largely based on the canonical flow of information from the entorhinal cortex through the trisynaptic loop-comprising the dentate gyrus and cornu ammonis regions CA3 and CA1-and back to cortex, where the hippocampus plays an important role in transforming relevant information into a usable storage system. This classic circuit has inspired current thinking on hippocampal functions related to learning, memory, and spatial navigation, but the potential functional contributions of other hippocampal areas, such as CA2, the fasciola cinereum, and the indusium griseum, and their integration of a major hypothalamic input, have been overlooked. These understudied circuits and nontraditional network dynamics such as dentate spikes have recently begun to yield fresh insights into unconventional circuit computations that extend the repertoire of hippocampal function beyond current models.

The exponential growth in academic publishing - exceeding 2 million papers annually 2023 - has rendered traditional systematic review methods unsustainable. These conventional approaches typically require 6-24 months for completion, creating critical delays between evidence availability and clinical implementation. While existing automation tools demonstrate workload reductions of 30-72.5%, their machine learning dependencies create barriers to immediate implementation. Additionally, direct AI screening methods involve substantial computational costs, lack real-time adaptability, suffer from inconsistent performance across different research domains, and provide no clear audit trail for regulatory compliance. We present a one-week systematic review acceleration protocol using rule-based automation where artificial intelligence (AI) assists with code generation. Researchers define screening criteria, then use AI language models (Claude, ChatGPT) as coding assistants. This protocol employs a two-phase screening process: (1) rule-based title/abstract screening and (2) rule-based full-text analysis, while adhering to established systematic review guidelines such as Cochrane methodology and PRISMA reporting. The rule-based system provides immediate implementation with complete transparency, while validation framework guides researchers in systematically testing screening sensitivity to minimize false negatives and ensure comprehensive study capture; meta-analysis and statistical synthesis remain manual processes requiring human expertise. We demonstrate the protocol's application through a case study examining cardiac fatty acid oxidation in heart failure with preserved ejection fraction (HFpEF), and validated through a separate review examining e-cigarette versus traditional cigarette cardiopulmonary effects, which successfully processed 3,791 records. This protocol represents a substantial advancement in systematic review methodology, making high-quality evidence synthesis more accessible across a broad range of scientific disciplines.