The medial habenula (MHb) and its main projection target, the interpeduncular nucleus (IPN), play an important role in mood/affect, anxiety, and the aversive experience associated with nicotine withdrawal. Given that MHb axons release glutamate onto IPN neurons, we investigated the expression and functional responses of ionotropic glutamate receptors (iGluRs) in neurons of the rostral IPN (IPR) in male rats. After confirming mRNA expression of and iGluR subunits in IPR, we employed glutamate uncaging coupled with two-photon imaging and patch-clamp electrophysiology. IPR dendrites, which often contained spine-like protrusions suggestive of synaptic contacts, featured a variety of response profiles following localized glutamate uncaging. Pharmacology experiments confirmed functional α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and -methyl-d-aspartate iGluR responses in IPR neuronal somata. Rats were trained to self-administer nicotine or saline during 10 fixed ratio 1 sessions and seven intermittent access sessions. In rats with a history of nicotine self-administration, perisomatic IPR iGluR responses are reduced. Acute nicotine application to slices from drug-naive rats recapitulated the effect of nicotine self-administration. These results identify a mechanism, whereby nicotine, even acute nicotine, may reduce IPR neuron sensitivity to glutamate from MHb axons, which could play a role in the aversive response to nicotine withdrawal.

Across brain regions and species, the dynamics and balance of excitation and inhibition critically determine neuronal firing. The hippocampal dentate gyrus is a brain area thought to be strongly regulated by inhibition. In-vivo, it exhibits remarkably sparse activity, a characteristic proposed to underlie computational tasks like pattern separation. Several populations of interneurons mediate strong feed-forward as well as feedback inhibition onto granule cells. However, how the dynamics of inhibition controls granule cell activity in-vivo is insufficiently studied. Using 2-photon in-vivo Ca-imaging in mice of either sex, we show that sensory stimulation activates only a small number of dentate gyrus granule cells, while inducing wide-spread inhibition across the remaining granule cell population. Dual-color imaging of both bulk medial perforant path activity and individual granule cell activity allowed us to probe input-output conversion in this pathway. To examine the interplay of MPP-evoked excitation and inhibition at the cellular level, we used in-vivo whole-cell patch-clamp recordings, while simultaneously photo-activating MPP inputs. Our findings reveal that MPP-triggered inhibition is fast, significantly larger than excitation, and long-lasting. These results reveal specific properties of inhibition in the dentate gyrus inhibition that are likely crucial for its computational functions, in maintaining sparse activity with a high signal-noise ratio. This study investigates the super- and sub-threshold computations of dentate gyrus granule cells to an incoming stimulus signal through the medial perforant path. This pathway is the main connection transferring information from the medial entorhinal cortex layer II into the hippocampus proper. The role of the granule cell network is thought to be crucial for the encoding of new environments and thereby the forming of new memories. Our data directly elucidate the in-vivo dynamics of excitation and inhibition in the dentate gyrus using both in-vivo imaging and electrophysiology. These findings add to the understanding of the overall sparse code of the dentate gyrus and can be crucial for future studies investigating how hippocampal codes are generated from entorhinal cortex inputs.

Repetitive mild traumatic brain injury (rmTBI) is a major contributor to long-term neurological dysfunction, yet many preclinical models lack precise control and quantification of biomechanical forces across impacts. We developed a reproducible, closed-skull mouse model of rmTBI using a custom-built weight-drop apparatus featuring a solenoid-based rebound arrest system, integrated high-speed videography, and accelerometry to track head kinematics during impact. Adult male and female mice received either a single impact or nine daily impacts. Linear and angular acceleration data were analyzed alongside behavioral and histological outcomes. Our apparatus delivered consistent impact and velocity forces with minimal inter-subject variability. Additionally, the animals experienced consistent linear and angular acceleration as measured using high-speed video capture. These impacts did not cause skull fracture or acute vascular hemorrhage, but impacted animals had increased return of righting reflex (RoRR) time, consistent with mild, concussion-like symptoms. Behavioral testing revealed reduced performance of rmTBI-affected mice in an olfaction-mediated foraging task (buried food task), particularly at later timepoints, consistent with progressive olfactory impairment. Immunohistochemical analysis of Iba1 and CD68 in the brain demonstrated sex-dependent microglial activation, with males showing higher expression levels in both single- and nine-impact models. Among the brain regions investigated, microglial activation was most pronounced in the corpus callosum, neocortex, and olfactory tubercle. These findings underscore the importance of including sex as a biological variable in rmTBI research and support the utility of this model for probing injury thresholds, regional vulnerability, and potential therapeutic interventions in repetitive head trauma. Mild traumatic brain injuries (mTBIs) contribute long-term sensory, motor, and cognitive dysfunction. We developed a novel approach for delivering repetitive mTBIs (rmTBIs) to mice via a custom weight-drop apparatus. The device allows precise control over impact forces and enables quantification of linear and angular acceleration during each impact. We describe the apparatus, the forces delivered, and the kinematics experienced by lightly anesthetized mice. We measured behavioral and neuroinflammatory sequelae in the brains of rmTBI-exposed mice compared to controls. rmTBI-exposed animals showed impairment in the olfaction-mediated buried food task and evidence of microglial reactivity in multiple brain regions days-to-weeks following injury. The results demonstrate the utility of this approach for studying rmTBI-associated pathophysiology, and for testing therapies or interventions for rmTBI.

People with epilepsy may experience sudden death due to respiratory failure through mechanisms that are currently not well understood. Epilepsy causing mutations are thought to elicit seizures due to altered function of forebrain circuits, yet breathing is controlled largely by the brainstem. To investigate how altered forebrain activity could impact breathing, we examined respiratory and seizure phenotypes in a mouse epilepsy model with a forebrain-specific deletion of the phosphatase and tensin homolog (PTEN) gene (PTEN-cKO). Using chronic diaphragm electromyography (EMG) and cortical electroencephalography (EEG), we monitored PTEN-cKO mice (6 males and 4 females) and control littermates (6 males and 3 females) continuously from pre-seizure onset through end-stage disease. PTEN-cKO mice develop spontaneous seizures that progress in frequency with age, accompanied by gradual changes in respiratory function, even during interictal periods. As seizure burden increases, PTEN-cKO mice experience an increased frequency of interictal apneas, slowing of respiratory rhythm, prolongation of inspiratory bursts, and elevation of inspiratory effort. All animals experienced a terminal apnea prior to cardiac arrest. These findings demonstrate that PTEN deletion in the forebrain disrupts the control of breathing and leads to terminal respiratory failure. Epilepsy typically alters forebrain function, but whether this alone is sufficient to alter the control of breathing, particularly in the absence of seizures, remains unclear. Here, we show in a spontaneous seizure model that forebrain-specific mutation of PTEN leads to progressive respiratory abnormalities initially manifesting as increased interictal apneas, then progressing to slower, deeper breathing and ultimately terminating in respiratory failure. These findings suggest that forebrain circuit dysfunction in epilepsy can disrupt respiratory control, potentially increasing the risk of sudden unexpected death in epilepsy (SUDEP).

The "sign-tracking" and "goal-tracking" model of individual variation in associative learning permits the identification of rats with different cue-reactivity and predisposition to addiction-like behaviors. Certainly, compared to "goal-trackers" (GTs), "sign-trackers" (STs) show more susceptibility traits such as increased cue-induced 'relapse' of drugs of abuse. Different cue- and reward-evoked patterns of activity in the nucleus accumbens (NAc) have been a hallmark of the ST/GT phenotype. However, it is unknown whether differences in the intrinsic neuronal properties of NAc medium spiny neurons (MSNs) in the core and shell subregions are also a physiological correlate of these phenotypes. We performed whole-cell slice electrophysiology in outbred male rats and found that STs exhibited the lowest excitability in the NAc core, with lower number of action potentials and firing frequency as well as a blunted voltage/current relationship curve in response to hyperpolarized potentials in both the NAc core and shell. Although firing properties of shell MSNs did not differ between STs and GTs, intermediate responders that engage in both behaviors showed greater excitability compared to both STs and GTs. These findings suggest that intrinsic excitability in the NAc may contribute to individual differences in the attribution of incentive salience. During associative learning, cues acquire predictive value, but in some instances, they also acquire incentive salience, meaning they take on some of the motivational properties of the reward. The propensity to attribute cues with incentive salience varies between individuals, and excessive attribution can lead to maladaptive behaviors. The "sign-and goal-tracking" model allows us to isolate these two properties and disambiguate the neurobiological processes that govern them. To our knowledge this is the first study characterizing passive and active membrane properties of MSNs in the NAc core and shell of STs and GTs, as well as IRs. These findings are meant to better inform investigations of the distinct role of the NAc in reward learning, particularly in the attribution of incentive salience and addiction predisposition.

Recent work showed unexpectedly large, daily modulation of intracellular chloride concentration ([Cl]) in cortical pyramidal cells, with consequences for GABAergic function and network excitability (Alfonsa et al., 2023; Pracucci et al., 2023). One explanation for this [Cl] modulation is that it arises from variation in presynaptic drive. In that case, neuronal classes with similar synaptic inputs should show correlated changes in activity-dependent ionic redistribution. To examine this prediction, we performed in vivo, LSSm-ClopHensor imaging to measure [Cl] and pH in populations of parvalbumin- (PV) and somatostatin-expressing (SST) interneurons in neocortical layer 2/3 of male and female adult mice. Imaging was performed at zeitgeber time (ZT) 5, and ZT17, when pyramidal cell [Cl] shows maximal divergence (Pracucci et al., 2023). Interestingly, PV interneurons also showed large physiological [Cl] modulation between these times, but out of phase with that in pyramidal cells, being raised at ZT5 and lower at ZT17, and with a far higher mean [Cl] SST interneurons showed less modulation, with higher variance, and with a temporal dynamic resembling the pyramidal cell pattern. Notably, in vitro experimental assays of inhibition, involving these two classes of interneuron, differed markedly at ZT5 and ZT17. The persistence of these time-of-day effects in vitro, and the difference in [Cl] dynamics between pyramidal cells and PV interneurons in vivo, both point towards cell-intrinsic regulation being more important than activity-dependent effects in setting these slow, daily, physiological, ionic redistribution patterns. We discuss what other possible factors may influence variations in brain state through the day. We find that the three largest subclasses of supragranular neocortical neurons, pyramidal cells and parvalbumin- and somatostatin-expressing interneurons, show different patterns of daily modulation of [Cl] Notably, the modulation in parvalbumin-interneurons is out-of-phase with the other two cell classes. We further observed differences in network inhibition in brain slices prepared at ZT5 and ZT17. We argue, based upon these various lines of evidence, that activity-dependent ionic redistribution is not the primary determinant of the slow daily [Cl] modulation. Instead, we discuss which cell-autonomous mechanisms may be involved, and what implications these findings have for our understanding of brain state differences.

Accurate electrode implantation in the subthalamic nucleus (STN) of rats is essential for high-quality electrophysiological and neuromodulation studies but remains technically challenging due to the small size and deep location of the STN. Traditional stereotactic methods, relying on bregma or averaged bregma-interaural based coordinates, often result in misplacement of electrode. Here, we introduce a combined anatomical and functional approach-bregma-interaural and electrophysiology-guided technique (BITE)- designed to enhance targeting accuracy for STN electrode implantation in male Sprague-Dawley rats. In this method, anterior-posterior (AP), medial-lateral (ML), and dorsal-ventral (DV) coordinates are initially determined using the average of bregma and interaural references. Electrode depth (DV axis) is fine-tuned based on real-time detection of characteristic STN neuronal firing patterns. If STN featured activity is not observed on the first implantation, additional adjustments in the AP and ML axes are made, followed by electrophysiology-guided DV tuning. Using BITE, we achieved an 83% overall success rate for STN electrode implantation, with 50% of electrodes precisely located in the dorsal STN (dSTN). This represents a significant improvement compared to the bregma-based method (17%, = 0.0005) and the averaged bregma-interaural based method (40%, = 0.0188). BITE offers two main advantages: (1) increased accuracy in targeting the STN, and (2) improved access to the dSTN, a region of growing interest in basal ganglia research. These findings demonstrate that BITE is a reliable and effective method for precise electrode placement in the STN and may serve as a valuable tool in rat models of deep brain stimulation and basal ganglia function. This study introduces BITE, a standardized method that combines anatomical referencing with electrophysiological confirmation to improve electrode implantation accuracy in the rat subthalamic nucleus (STN). By averaging bregma-interaural coordinates, BITE inimizes the impact of bregma misidentification on implantation accuracy, while real-time STN firing patterns guide fine adjustments and confirm electrode placement. The method includes a rescue strategy for failed initial implantation, significantly improving overall success. BITE achieved an 83% implantation success rate, with 50% of electrodes precisely placed in the dorsal STN (dSTN). This approach shows strong potential for accurate targeting of dSTN and may be adaptable for broader applications in rat brain surgeries. Further validation is needed to confirm its utility across other brain regions.

Neural signals necessary for gaze holding are produced in the excitatory networks of oculomotor neural integrators including the prepositus hypoglossi nucleus (PHN) and the interstitial nucleus of Cajal (INC). Our previous studies have shown that the activation of the networks can be evaluated by sustained excitatory postsynaptic current (EPSC) responses , in which a higher EPSC frequency after burst stimulation (100 Hz, 20 trains) than the frequency before the stimulation lasts for more than 1 s. Both the PHN and the INC receive serotonergic inputs mainly from the dorsal raphe nucleus, and serotonin (5-HT) induces depolarizing responses via 5-HT or 5-HT receptors and hyperpolarizing responses via 5-HT receptors in PHN and INC neurons. However, how 5-HT affects sustained EPSC responses remains unknown. In this study, we investigated the effects of 5-HT on sustained EPSC responses using whole-cell recordings in brainstem slices obtained from rats of either sex. Compared with the control treatment, bath application of 10 μM 5-HT significantly reduced the duration and frequency of the EPSC responses in the PHN and the INC. The application of 8-OH-DPAT, an agonist of the 5-HT receptor, suppressed sustained EPSC responses, but agonists of the 5-HT and 5-HT receptors had no effect on the responses, indicating that 5-HT has a suppressive effect on sustained EPSC responses via 5-HT receptors. These results suggest that neurons that express 5-HT receptors participate in excitatory networks and that the suppressive effect of 5-HT can facilitate exploratory behavior through eye movements rather than gaze holding. Excitatory networks of brainstem oculomotor neural integrators are involved in gaze holding. Although neural integrators receive serotonergic inputs, how serotonergic inputs modulate the activity of excitatory networks remains unknown. We investigated the effect of serotonin (5-HT) on network activity using whole-cell recordings in brainstem slices. The finding that 5-HT suppressed network activity via 5-HT receptors but not via 5-HT and 5-HT receptors indicates that 5-HT suppresses network activity via 5-HT receptors. This finding suggests that the neurons that express 5-HT participate in the excitatory networks of oculomotor neural integrators and that the suppressive effect of 5-HT can facilitate exploratory behavior through eye movements rather than gaze holding.

Mice offer a wealth of opportunities for investigating brain circuits regulating multiple behaviors, largely due to their genetic tractability. Social behaviors are translationally relevant, considering both mice and humans are highly social mammals, and human social behavior disruptions are key symptoms of myriad neuropsychiatric disorders. Stresses related to social experiences are particularly influential in the severity and maintenance of neuropsychiatric disorders like anxiety disorders, and trauma and stressor-related disorders. Yet, induction and study of social stress in mice has disproportionately focused on males, influenced heavily by their inherent territorial nature. Social target-instigated stress (i.e., defeat), while ethologically relevant, is quite variable and predominantly specific to males, making rigorous and sex-inclusive studies challenging. In pursuit of a controllable, consistent, high throughput, and sex-inclusive method for social stress elicitation, we modified a paradigm to train male and female F1 129S1/SvlmJ × C57BL/6J mice to associate (via classical conditioning) same or different sex C57BL/6J targets with a mild, aversive stimulus. While further paradigm optimization is required, social interaction testing 24 h after conditioning indicates males socially conditioned better to male targets by exhibiting reduced social interaction, whereas females appeared not to form social stimulus associations. Serum corticosterone levels inversely corresponded to social avoidance after different sex, but not same sex, conditioning, suggesting corticosterone-mediated arousal influences cross-sex interactions. These rigorously controlled null outcomes align with past pursuits' limited success in creating a sex-inclusive social stress paradigm. Validated paradigms to study social stress in female mice, and across sexes, are needed. We modified a published male mouse protocol by using classical conditioning to pair an aversive stressor with a target. Our goal was to create a uniform, cross-sex, high-throughput social stress technique to advance future research. Though our modified paradigm requires future improvements, we did acquire evidence that males can be socially conditioned in this way, and female same sex social engagement can be attenuated by a preceding non-social aversive experience. These null findings, while not achieving our goal, provide useful information to advance future sex-inclusive social stress investigations.

This study determined the association between the triglyceride-glucose (TyG) index-waist-to-hip ratio (TyG-WHR) and stroke. Data from the China Health and Retirement Longitudinal Study (CHARLS) were utilized from baseline in 2011 to the wave six follow-up in 2020. The CHARLS cohort was assembled using a multistage probability sampling technique. Participants were comprehensively assessed through standardized questionnaires with face-to-face interviews. A total of 4,911 patients with 2,338 males (47.6%) and 2,573 females (52.4%) were included in this analysis. A significant association between the TyG-WHR and the risk of stroke was identified utilizing a Cox proportional hazards regression model with cubic spline functions that were characterized by a nonlinear relationship. The analysis determined a threshold for the TyG-WHR at 4.635. The association between the TyG-WHR and stroke was not significant [hazard ratio (HR), 0.813; 95% CI, 0.662-0.999;  = 0.049] to the left of the threshold. The association was statistically significant (HR, 1.271; 95% CI, 1.131-1.429;  < 0.001) to the right of the threshold. The current study demonstrated a positive and nonlinear association between the TyG-WHR and stroke risk among middle-aged and elderly Chinese populations. When the TyG-WHR exceeded 4.635, there was a statistically significant positive correlation with the occurrence of stroke. Clinically, reducing the TyG-WHR, especially <4.635, may reduce the risk of stroke.

A central mechanism of exposure-based cognitive behavioral therapy for anxiety and trauma-related disorders is fear extinction. However, the mechanisms underlying fear extinction are deficient in some individuals, leading to treatment resistance. Recent animal studies demonstrate that upon omission of the aversive, unconditioned stimulus (US) during fear extinction, dopamine (DA) neurons in the ventral tegmental area (VTA) produce a prediction error (PE)-like signal. However, whether this VTA-DA neuronal PE-like signal is altered in animals exhibiting deficient fear extinction has not been studied. Here, we used a mouse model of impaired fear extinction [129S1/SvImJ (S1) inbred mouse strain] to monitor and manipulate VTA-DA neurons during extinction. Male DAT-Cre mice backcrossed onto an S1 background (S1-DAT-Cre) exhibited impaired extinction but normal VTA-DA neuron number, as compared with BL6-DAT-Cre mice. In vivo fiber photometry showed that impaired extinction in male S1-DAT-Cre mice was associated with abnormally sustained US omission-related VTA-DA neuronal calcium activity during extinction training and retrieval. Neither in vivo optogenetic photoexcitation of VTA-DA neuronal cell bodies nor their axons in the infralimbic cortex was sufficient to rescue deficient extinction in male S1-DAT-Cre mice, at least within the optogenetic and behavioral parameters used. These data suggest that alterations in the activity of VTA-DA neurons during extinction learning and retrieval may be associated with deficient fear extinction in male S1 mice and could potentially contribute to extinction impairments in patient populations.

Ongoing efforts over the last 50 years have made data and methods more reproducible and transparent across the life sciences. This openness has led to transformative insights and vastly accelerated scientific progress (Gražulis et al., 2012; Munafó et al., 2017). For example, structural biology (Bruno and Groom, 2014) and genomics (Benson et al., 2013; Porter and Hajibabaei, 2018) have undertaken systematic collection and publication of protein sequences and structures over the past half century. These data, in turn, have led to scientific breakthroughs that were unthinkable when data collection first began (Jumper et al., 2021). We believe that neuroscience is poised to follow the same path, and that principles of open data and open science will transform our understanding of the nervous system in ways that are impossible to predict at the moment. New social structures supporting an active and open scientific community are essential (Saunders, 2022) to facilitate and expand the still limited adoption of open science practices in our field (Schottdorf et al., 2024). Unified by shared values of openness, we set out to organize a symposium for open data in neurophysiology (ODIN) to strengthen our community and facilitate transformative open neuroscience research at large. In this report, we synthesize insights from this first ODIN event. We also lay out plans for how to grow this movement, document emerging conversations, and propose a path toward a better and more transparent science of tomorrow.

Identifying neural signatures of slow-wave sleep (SWS) is important for a number of reasons including diagnosing potential sleep disorders and examining its role in memory consolidation ( Diekelmann and Born, 2010; Klinzing et al., 2019; Brodt et al., 2023). Studies of sleep in the common marmoset () have revealed similarities to humans and other nonhuman primates, including distinct sleep stages ( Crofts et al., 2001) and diurnal sleep patterns ( Hoffmann et al., 2012). Advances in applying wireless technology for recording neural activity during natural, unrestrained behaviors ( Walker et al., 2021) position the marmoset as an excellent model for studying sleep-related neural activity associated with learning. Here, we identify putative SWS epochs based on the spatially correlated activity of local field potentials (LFPs) recorded from a multielectrode planar array implanted in the sensorimotor cortex of two marmosets (one female and one male). The average correlation of the LFP signal measured between electrodes decreased gradually with the distance between pairs. We modeled this spatial structure as an exponential decay function, where the spatial decay constant varied significantly over time, reaching its lowest values during epochs where LFP power dynamics were consistent with SWS. These periods of widespread high correlations across the sensorimotor cortex closely matched SWS identification commonly used in rodent models based on the changes in power in the gamma (30-60 Hz) and delta/slow oscillation (0.1-4 Hz) frequency bands. These findings demonstrate that putative SWS epochs can be reliably identified using spatially correlated LFP activity across the sensorimotor cortex.

ArfGAP, with dual PH domain-containing protein 1/Centaurin-α1 (ADAP1/CentA1), is a brain-enriched and highly conserved Arf6 GTPase-activating and Ras-anchoring protein. CentA1 is involved in dendritic outgrowth and arborization, synaptogenesis, and axonal polarization by regulating the actin cytoskeleton dynamics. CentA1 upregulation and association with amyloid plaques in the human Alzheimer's disease (AD) brain suggest the role of this protein in AD progression. To understand the role of CentA1 in neurodegeneration, we crossbred CentA1 knock-out (KO) mice with the J20 mouse model of AD. We evaluated AD-associated behavioral and neuropathological hallmarks and gene expression profiles in J20 and J20 crossed with CentA1 KO (J20xKO) male mice to determine the impact of eliminating CentA1 expression on AD-related phenotypes. Spatial memory assessed by the Morris water maze test showed significant impairment in J20 mice, which was rescued in J20xKO mice. Moreover, neuropathological hallmarks of AD, such as amyloid plaque deposits and neuroinflammation, were significantly reduced in J20xKO mice. To identify potential mediators of AD phenotype rescue, we analyzed differentially expressed genes between genotypes. We found that changes in the gene profile by deletion of CentA1 from J20 (J20xKO vs J20) were anticorrelated with changes caused by APP overexpression (J20 vs wild type), consistent with rescue of J20 phenotypes by CentA1 KO. In summary, our data indicate that CentA1 is required for the progression of AD phenotypes in this model and that targeting CentA1 signaling might have therapeutic potential for AD prevention or treatment.

Structural changes in dendritic spines underlie long-term potentiation (LTP). While CaMKII has been considered as the primary driver of these changes, we show that transient, localized activation of Rac1 alone is sufficient to induce structural LTP in hippocampal slices prepared from rat pups of either sex. Using photoactivatable Rac1 (PA-Rac1), we demonstrated that Rac1 activation triggers spine enlargement and actin polymerization. This PA-Rac1-induced plasticity was blocked by Rac1 and Pak1 inhibitors but not by a CaMKII inhibitor. Our results identify Rac1 as an upstream of persistent signaling that stabilizes actin-based spine structural changes critical for synaptic memory encoding.

Signaling at nicotinic acetylcholine receptors (nAChRs) is vital for normal development of cerebral cortical circuits. These developing circuits are also shaped by fast-spiking (FS) inhibitory cortical neurons. While nicotinic dysfunction in FS neurons is implicated in a number of psychiatric and neurodevelopmental disorders, FS neurons are thought to not have nicotinic responses in adults. Here, we establish a timeline of FS neuron response to nicotine pre- and postsynaptically in primary somatosensory cortex in male and female rats. We found that nicotine increases the frequency of spontaneous synaptic inputs to FS neurons during the second postnatal week, and this effect persisted through development. In contrast, FS neurons in S1 had no postsynaptic responses to nicotine from as early as they can be reliably identified. This was not attributable to receptor desensitization, and we further revealed that FS neurons express abundant mRNA for several nAChR subunits, beginning early in development. To determine why FS neurons do not respond to nicotine despite expressing these receptors, we probed for the expression of lynx1, a negative nicotinic modulator. Lynx1 mRNA was expressed in FS neurons from early development, with expression increasing dramatically during the second postnatal week.

RNA localization to neuronal axons and dendrites provides spatiotemporal control over gene expression to support synapse function. Neuronal messenger RNAs (mRNAs) localize as ribonucleoprotein particles (RNPs), commonly known as RNA granules, the composition of which influences when and where proteins are made. High-throughput sequencing has revealed thousands of mRNAs that localize to the hippocampal neuropil. Whether these mRNAs are spatially organized into common RNA granules or distributed as independent mRNAs for proper delivery to synapses is debated. Here, using highly multiplexed single molecule fluorescence in situ hybridization (HiPlex smFISH) and colocalization analyses, we investigate the subcellular spatial distribution of 15 synaptic neuropil localized mRNAs in the male and female rodent hippocampus. We observed that these mRNAs are present in the neuropil as heterogeneously sized fluorescent puncta with spatial colocalization patterns that generally scale by neuropil mRNA abundance. Indeed, differentially expressed mRNAs across cell types displayed colocalization patterns that scaled by abundance, as did simulations that reproduce cell-specific differences in abundance. Thus, the probability of these mRNAs colocalizing in the neuropil is best explained by stochastic interactions based on abundance, which places constraints on the mechanisms mediating efficient transport to synapses. RNA localization establishes compartment-specific gene expression that is critical for synapse function. Thousands of mRNAs localize to the hippocampal synaptic neuropil, however, whether mRNAs are spatially organized as similar or distinctly composed ribonucleoprotein particles for delivery to synapses is unknown. Using multiplexed smFISH to assess the spatial organization of 15 neuropil localized mRNAs, we find that these mRNAs are present in variably sized puncta suggestive of heterogeneous transcript copy number states. RNA colocalization analyses in multiple hippocampal cell types suggest that the spatial relationship of these mRNAs is best described by their abundance in the neuropil. Stochastic RNA-RNA interactions based on neuropil abundance are consistent with models indicating that global principles, such as energy minimization, influence population localization strategies.

Listening effort reflects the cognitive and motivational resources allocated to speech comprehension, particularly under challenging conditions. Visual cues are known to enhance speech perception, potentially by reducing the cognitive demands of the task. However, the neurophysiological mechanisms underlying this facilitation, especially in terms of effort-related changes, remain unclear. In this study, we combined pupillometry and electroencephalography (EEG) to investigate how visual speech cues modulate cognitive effort during speech recognition. Twenty-two participants (seven females) performed a speech-in-noise task under three modalities: (1) auditory-only, (2) audiovisual, and (3) visual-only. Task difficulty was manipulated via signal-to-noise ratio (SNR) in the first two modalities. Firstly, we found an inverted U-shape relationship between pupil dilation and frontal midline theta with SNR for audiovisual and auditory-only speech, consistent with prior models of effort allocation. Secondly, we observed the SNR at which the neurophysiological measures peaked was at a lower SNR for audiovisual speech. Surprisingly, we found pupil dilation to be larger overall in audiovisual speech, while frontal midline theta did not show differences in either modality. These findings highlight the complexity of interpreting physiological markers of effort and suggest that visual cues may alter the temporal dynamics or resource allocation strategies during speech processing. Our results support the extension of auditory-based models of listening effort to audiovisual contexts and underscore the value of integrating multimodal neurophysiological measures to better understand the cognitive and neural mechanisms of effortful listening.

Dopamine release in the nucleus accumbens (NAc) is classically linked to associative learning, signaling relationships between predictive cues and outcomes. Yet, dopamine is also strongly modulated by novelty, a non-associative factor that has received comparatively little attention. Here, we used optical dopamine sensors in awake, behaving male and female mice to define how novelty alters the temporal dynamics of dopamine release during aversive learning. We manipulated novelty in three ways: (1) omitting expected footshocks, (2) introducing novel neutral cues concurrently with shock-predictive stimuli, and (3) presenting novel stimuli in an unpaired fashion within a context. Across all conditions, manipulations robustly increased dopamine release and in some cases altered the directionality of cue-evoked dopamine responses. Notably, these effects extended beyond the immediate stimulus window, altering subsequent responses to both conditioned cues and footshocks. Together, these findings demonstrate that changes in the environment that extend beyond prediction-based learning can exert a powerful and sustained influence on dopamine signaling, reshaping how aversive cues and outcomes are represented in the brain. Novelty strongly shapes how organisms learn and adapt by influencing dopamine signaling in the brain. This study shows that novelty alters dopamine responses to both conditioned and unconditioned aversive stimuli, with effects that persist across short and extended timescales. These findings reveal that novelty is a key factor modulating dopamine dynamics during learning and highlight its broader role in guiding adaptive behavioral responses to changing environments.

Higher education (HE) is undergoing rapid transformation, shaped as a result of the COVID-19 pandemic, the expansion of digital learning, and the increasing presence of artificial intelligence (AI). For educators, these shifts raise important questions about their evolving purpose and responsibilities. In this commentary, we reflect on the role of bioscience educators in the United Kingdom, highlighting the enduring need for human connection, empathy, and belonging in teaching, alongside the integration of digital tools. We discuss changing student motivations, the necessity of flexible and inclusive learning environments, and the balance between traditional practices and innovative pedagogies. Practical training, active learning, and responsible engagement with emerging technologies remain central to equipping students with transferable skills such as adaptability, critical thinking, and resilience. We argue that while digital innovations can enhance accessibility and engagement, they cannot replace the uniquely human dimensions of teaching. Ultimately, bioscience educators must embrace their dual role as facilitators and lifelong learners, modeling curiosity, vulnerability, and inclusivity to empower students to thrive in an increasingly complex world.

Decoding algorithms provide a powerful tool for understanding the firing patterns that underlie cognitive processes such as motor control, learning, and recall. When implemented in the context of a real-time system, decoders also make it possible to deliver feedback based on the representational content of ongoing neural activity. That in turn allows experimenters to test hypotheses about the role of that content in driving downstream activity patterns and behaviors. While multiple real-time systems have been developed, they are typically implemented with a compiled programming language, making them more difficult for users to quickly adapt for new experiments. Here we present a software system written in the widely-used Python programming language to facilitate rapid experimentation. Our solution implements the state-space based clusterless decoding algorithm for an online, real-time environment. The parallelized application processes neural data with temporal resolution of 6 ms and median computational latency <50 ms for medium- to large-scale (32+ tetrodes) rodent hippocampus recordings without the need for spike sorting. It also executes auxiliary functions such as detecting sharp wave ripples from local field potential (LFP) data. Even with an interpreted language, the performance is similar to state-of-the-art solutions which use compiled programming languages. We demonstrate this real-time decoder in a rat behavior experiment in which the decoder allowed closed loop neurofeedback based on decoded hippocampal spatial representations. Overall this system provides a powerful and easy-to-modify tool for real-time feedback experiments. We developed a pure Python software system to decode hippocampal spiking activity in real time without the need for spike sorting. Our solution was validated in a real-time closed loop experiment and can be customized for different data acquisition systems. This represents a valuable new resource to enable experiments requiring low-latency, closed-loop interaction with the information encoded in neural ensembles.