Behavioral Neuroscience publications

Tissue inflammation or nerve injury at the periphery can cause chronic pain. Although the spinal-cord-projecting neurons in the rostral ventromedial medulla (RVMSC neurons) can promote pain chronification1-4, the pathway by which peripheral injury signals drive these neurons is poorly understood1-3,5. Here we report a circuit loop that extends from the spinal cord to the ventral posterolateral thalamus and posterior complex of the thalamus, proceeds to the primary somatosensory cortex and returns to the spinal cord via the lateral superior colliculus, which in turn connects to μ-opioid-receptor-expressing RVMSC neurons. Silencing any node along this multisynaptic circuit has minimal effects on nociception in healthy mice, but can eliminate mechanical hypersensitization and restore normal nociceptive response thresholds in mouse models of inflammatory and neuropathic pain. In healthy mice, repetitive-but not acute-activation of each node in this circuit is sufficient to cause robust chronic mechanical hypersensitization. Our findings reveal a spino-brain-spinal cord circuit loop that links ascending and descending pathways and specifically drives chronic mechanical pain. This could enable the identification of cellular targets for treating chronic pain.

The lateral preoptic area (LPO) is a functionally heterogeneous hypothalamic structure that is increasingly recognised for its role in motivated and drug‐seeking behaviours. Although prior studies have shown that LPO neurons exhibit diverse activity patterns during cocaine self‐administration, the specific contributions of glutamatergic and GABAergic populations to conditioned responses to cocaine remain unclear. In this study, we recorded the activity of LPO glutamatergic ( vglut2 ‐expressing) and GABAergic ( vgat ‐expressing) neuronal subpopulations during cocaine conditioning to identify how these cell types respond to drug‐associated cues in awake, behaving mice. Our results revealed that, after cocaine conditioning, both glutamatergic and GABAergic populations showed reduced activity upon entry into the cocaine‐paired chamber. However, only glutamatergic neurons exhibited increased activity when mice entered the saline‐paired chamber. The magnitude of these activity changes was also correlated with behavioural outcomes: reduced GABAergic activity was associated with greater preference for the cocaine‐paired chamber, whereas stronger glutamatergic responses were associated with greater preference for the saline‐paired chamber. These findings indicate that LPO GABAergic and glutamatergic neurons exhibit distinct, cell type–specific patterns during cocaine‐conditioned place preference. Rather than indicating opposing motivational states, the results highlight that LPO activity relates to conditioned behaviours in a cell type– and context‐dependent manner. By linking activity in glutamatergic and GABAergic neurons with conditioned responses, this work provides initial evidence for how LPO circuits may contribute to drug‐associated learning.

The basal ganglia play a key role in visual perceptual decisions. Despite being the primary target in the basal ganglia for inputs from the visual cortex, the posterior striatum's (PS) involvement in visual perceptual behavior remains unknown in rodents. We reveal that the PS direct pathway is largely segregated from the dorsomedial striatum (DMS) direct pathway, the other major striatal target for the visual cortex. We investigated the role of the PS in visual perceptual decisions by optogenetically stimulating striatal medium spiny neurons in the direct pathway (D1-MSNs) of male and female mice performing a visual change-detection task. PS D1-MSN activation robustly biased visual decisions in a manner dependent on visual context, timing, and reward expectation. We examined the effects of PS and DMS direct pathway activation on neuronal activity in the superior colliculus (SC), a major output target of the basal ganglia. Activation of either direct pathway rapidly modulated SC neurons but mostly targeted different SC neurons and had opposite effects. These results demonstrate that the PS in rodents provides an important route for controlling visual decisions, in parallel with the better-known DMS and with distinct anatomical and functional properties.

Visual selective attention is not wired into the brain fully formed and immutable but is acquired and refined as animals learn by interacting with their environment. Here we investigated this process by studying neuronal activity in the superior colliculus (SC) of male and female mice that learned different meanings of the same visual stimuli. We recorded spiking activity of neurons across the superficial and deep SC layers in three cohorts of mice, each trained using a tailored set of task rules that attributed different levels of behavioral relevance to the visual stimuli. Experimental conditions across the three tasks were carefully matched for visual stimulation and task engagement. We found that several markers of attention-related activity depended on the level of learned behavioral relevance, with the strongest effects in deep SC. First, for activity evoked by cue onset, visual responses in superficial SC were larger in animals that exhibited higher learned relevance. In deep SC, the presence of visual onset responses depended entirely on the learned behavioral relevance. Second, traditional attention-related modulation, defined as enhanced steady-state activity for the visual stimulus at the cued location, was also stronger with higher learned relevance, and this effect was limited to deep SC. Finally, the response to the visual change at the cued location was virtually absent when learned behavioral relevance was low but was prominent after visual training. Together, these results reveal that several fundamental features of attention-related modulation depend on the behavioral relevance learned through task-specific training, including aspects of stimulus-driven attention.

The thalamocortical pathways exhibit neuroplasticity not only during the critical period but also in adulthood. In this study, we investigated how cholecystokinin (CCK) modulates age-dependent thalamocortical plasticity. Our findings demonstrated that CCK is expressed in thalamocortical neurons and that high-frequency stimulation (HFS) of the thalamocortical pathway triggers the release of CCK in auditory cortex (ACx), as detected by a CCK sensor. HFS of the medial geniculate body (MGB) induced thalamocortical long-term potentiation (LTP) in wild-type young adult mice. However, knockdown of CCK expression in MGB neurons or blockade of the CCK-B receptor (CCKBR) in the ACx abolished HFS-induced LTP. Interestingly, this LTP could not be elicited in juvenile (3-week-old) or aged mice (over 18-month-old) due to distinct mechanisms: the absence of CCKBR in juveniles and the inability to release CCK in aged mice. Notably, exogenous administration of CCK into the ACx rescued LTP in aged mice and significantly improved frequency discrimination. These findings highlight the potential of CCK as a therapeutic intervention for ameliorating neuroplasticity deficits associated with thalamocortical connectivity.

The dopaminergic system is crucial for affect regulation. Melanocortin 4 receptors (MC4R) in the ventral striatum have been shown to be necessary for establishing aversive states. Here, we functionally characterize MC4R-expressing striatal neurons in mice. MC4Rs were enriched in atypical dopamine receptor 1 (D1) neurons in the lateral stripe of the striatum (LSS), an understudied area in the ventrolateral striatum. Fiber photometry recordings showed that MC4R neuron activity and local dopamine release in the LSS increased in response to both rewarding and aversive stimuli. Moreover, MC4R neuronal activity and glutamate release in the LSS correlated with body movement. Optogenetic activation of MC4R-LSS neurons was rewarding in a real-time place preference test and a self-stimulation paradigm, increased locomotor activity, and induced striatal dopamine release. Collectively, our findings suggest that MC4R-LSS neurons are activated by stimuli of both rewarding and aversive character and that they induce positive affect, dopamine release and locomotion.

Animals learn the value of foods on the basis of their postingestive effects and thereby develop aversions to foods that are toxic 1–10 and preferences to those that are nutritious 11–13 . However, it remains unclear how the brain is able to assign credit to flavours experienced during a meal with postingestive feedback signals that can arise after a substantial delay. Here we reveal an unexpected role for the postingestive reactivation of neural flavour representations in this temporal credit-assignment process. To begin, we leverage the fact that mice learn to associate novel 14,15 , but not familiar, flavours with delayed gastrointestinal malaise signals to investigate how the brain represents flavours that support aversive postingestive learning. Analyses of brain-wide activation patterns reveal that a network of amygdala regions is unique in being preferentially activated by novel flavours across every stage of learning (consumption, delayed malaise and memory retrieval). By combining high-density recordings in the amygdala with optogenetic stimulation of malaise-coding hindbrain neurons, we show that delayed malaise signals selectively reactivate flavour representations in the amygdala from a recent meal. The degree of malaise-driven reactivation of individual neurons predicts the strengthening of flavour responses upon memory retrieval, which in turn leads to stabilization of the population-level representation of the recently consumed flavour. By contrast, flavour representations in the amygdala degrade in the absence of unexpected postingestive consequences. Thus, we demonstrate that postingestive reactivation and plasticity of neural flavour representations may support learning from delayed feedback.

The medial prefrontal cortex (mPFC) and hippocampus are critical for memory retrieval, decision making, and emotional regulation. While ventral CA1 (vCA1) shows direct and reciprocal connections with mPFC, dorsal CA1 (dCA1) forms indirect pathways to mPFC, notably via the thalamic reuniens nucleus (Re). Neuroanatomical tracing has documented structural connectivity of this indirect pathway through Re however, its functional operation is largely unexplored. Here, we used in vivo and in vitro electrophysiology along with optogenetics to address this question. Whole-cell patch-clamp recordings in acute mouse brain slices revealed both monosynaptic excitatory responses and disynaptic feedforward inhibition at Re–mPFC synapses. However, we also identified a prolonged excitation of mPFC by Re. These early monosynaptic and late recurrent components are in marked contrast to the primarily feedforward inhibition characteristic of thalamic inputs to the neocortex. Local field potential recordings in mPFC brain slices revealed prolonged synaptic activity throughout all cortical lamina upon Re activation, with the late excitation enhanced by blockade of parvalbumin neurons and GABA A Rs. In vivo Neuropixels recordings in head-fixed awake mice revealed a similar prolonged excitation of mPFC units by Re activation. In summary, Re output produces recurrent feedforward excitation within mPFC suggesting a potent amplification system in the Re–mPFC network. This may facilitate amplification of dCA1->mPFC signals for which Re acts as the primary conduit, as there is little direct connectivity. In addition, the capacity of mPFC neurons to fire bursts of action potentials in response to Re input suggests that these synapses have a high gain.

Dopamine (DA) signals to the striatum play critical roles in shaping and sustaining stimulus-reward associations. In primates, however, the dynamics of the DA signals remain unknown since conventional methods are not necessarily appropriate in terms of the spatiotemporal resolution or chemical specificity sufficient for detecting the DA signals. In our study, fiber photometry with a fluorescent DA sensor was employed to identify reward-related DA transients in the monkey striatum. This technique, which directly monitors local DA release, reveals a reward prediction error signal in the anterior putamen originating from midbrain DA neurons. Further, DA transients in the head of the caudate nucleus exhibit a value-based response to reward-predicting stimuli. These signals have been found to arise from two separate groups of DA neurons in the substantia nigra pars compacta. The present results demonstrate that fluorescence DA monitoring is applicable to detect DA signals in the primate striatum for investigating their roles.

Neural dynamics are thought to reflect computations that relay and transform information in the brain. Previous studies have identified the neural population dynamics in many individual brain regions as a trajectory geometry, preserving a common computational motif. However, whether these populations share particular geometric patterns across brain-wide neural populations remains unclear. Here, by mapping neural dynamics widely across temporal/frontal/limbic regions in the cortical and subcortical structures of monkeys, we show that 10 neural populations, including 2,500 neurons, propagate visual item information in a stochastic manner. We found that visual inputs predominantly evoked rotational dynamics in the higher-order visual area, TE, and its downstream striatum tail, while curvy/straight dynamics appeared frequently downstream in the orbitofrontal/hippocampal network. These geometric changes were not deterministic but rather stochastic according to their respective emergence rates. Our meta-analysis results indicate that visual information propagates as a heterogeneous mixture of stochastic neural population signals in the brain.

Face processing models propose gradually more complex receptive field properties culminating in invariant representations in anterior inferotemporal cortex (aITC), leading to late socio-emotionally relevant encoding in pre- and orbitofrontal cortex (POC). Top-down facilitation models, however, predict that some lower-level POC neurons respond faster than aITC. To resolve this discrepancy, we recorded from 2,459 neurons in fMRI-defined POC and aITC face patches. POC patches are more heterogeneous, containing smaller fractions of face-selective neurons than aITC and a mixture of responses to faces and non-faces. In one POC patch, face responses are surprisingly fast, outpacing those in aITC. Moreover, its responses correlate inversely with stimulus spatial frequency. Hence, our extensive data, with a large diversity of POC neurons, support both models and suggest one POC face patch might be specialized in fast, low-level face processing, which may enable (partially) invariant face representations during subsequent processing stages in inferotemporal cortex (ITC).

High-frequency stimulation (HFS)-induced long–term potentiation (LTP) is generally regarded as a homosynaptic Hebbian-type LTP, where synaptic changes are thought to occur at the synapses that project from the stimulation site and terminate onto the neurons at the recording site. In this study, we first investigated HFS-induced LTP on urethane-anesthetized rats and found that cortical HFS enhances neural responses at the recording site through the strengthening of local connectivity with nearby neurons at the stimulation site rather than through synaptic strengthening at the recording site. This enhanced local connectivity at the stimulation site leads to increased output propagation, resulting in signal potentiation at the recording site. Additionally, we discovered that HFS can also nonspecifically strengthen distant afferent synapses at the HFS site, thereby expanding its impact beyond local neural connections. This form of plasticity exhibits a neo-Hebbian characteristic as it exclusively manifests in the presence of cholecystokinin release, induced by HFS. The cortical HFS-induced local LTP was further supported by a behavioral task, providing additional evidence. Our results unveil a previously overlooked mechanism underlying cortical plasticity: synaptic plasticity is more likely to occur around the soma site of strongly activated cortical neurons rather than solely at their projection terminals.

Autism Spectrum Disorders (ASDs) are a group of neurodevelopmental disorders with heterogeneous causes, and are characterized by communication deficits, impaired social interactions, and repetitive behaviors. Despite numerous studies in mouse models focused on pathophysiological circuit mechanisms of ASD in mature animals, little is known regarding ASD onset and its evolution through development. The medial prefrontal cortex (mPFC) is crucial for higher-order cognitive functions and social behavior, thus key to understanding ASD pathology. To explore early developmental disruptions in the mPFC, we used the Shank3 knockout (Shank3 −/− ) mouse model. SHANK3 is crucial for glutamatergic synapse maturation, and the Shank3 −/− mouse has been well-characterized for displaying ASD-related behavioral phenotypes. We investigated network, cellular, and synaptic changes within the mPFC and in its projections to the mediodorsal thalamus (MD) at two developmental stages, preweaning (P14) and adulthood (>P55). Our findings reveal early synaptic deficits at P14 both within the mPFC and in its projections to the MD accompanied by alterations in mPFC network activity and reduced excitability of excitatory neurons, overall suggesting hypofunction. Interestingly, behavioral deficits were already detectable by P11, preceding the observation of synaptic changes at P14. By adulthood, these early synaptic and cellular alterations progressed to global dysfunction, characterized by mPFC network hyperfunction and layer 5 pyramidal cell hyperexcitability, accompanied by augmented glutamatergic signaling to MD with enhanced action potential production. These results suggest that early synaptic changes may precede and interact with behavioral deficits, potentially leading to compensatory mechanisms that contribute to more pronounced mPFC dysfunction later in development. This study highlights the complex dynamic progression of mPFC deficits in ASD and emphasizes the potential impact of targeting early synaptic alterations to mitigate later behavioral and cognitive deficits.

The entorhinal cortex is involved in establishing enduring visuo-auditory associative memory in the neocortex. Here we explored the mechanisms underlying this synaptic plasticity related to projections from the visual and entorhinal cortices to the auditory cortex in mice using optogenetics of dual pathways. High-frequency laser stimulation (HFS laser) of the visuo-auditory projection did not induce long-term potentiation. However, after pairing with sound stimulus, the visuo-auditory inputs were potentiated following either infusion of cholecystokinin (CCK) or HFS laser of the entorhino-auditory CCK-expressing projection. Combining retrograde tracing and RNAscope in situ hybridization, we show that Cck expression is higher in entorhinal cortex neurons projecting to the auditory cortex than in those originating from the visual cortex. In the presence of CCK, potentiation in the neocortex occurred when the presynaptic input arrived 200 ms before postsynaptic firing, even after just five trials of pairing. Behaviorally, inactivation of the CCK + projection from the entorhinal cortex to the auditory cortex blocked the formation of visuo-auditory associative memory. Our results indicate that neocortical visuo-auditory association is formed through heterosynaptic plasticity, which depends on release of CCK in the neocortex mostly from entorhinal afferents.

The lateral hypothalamus (LH) is involved in feeding behavior and defense responses by interacting with different brain structures, including the Ventral Tegmental Area (VTA). Emerging evidence indicates that LH-glutamatergic neurons infrequently synapse on VTA-dopamine neurons but preferentially establish multiple synapses on VTA-glutamatergic neurons. Here, we demonstrated that LH-glutamatergic inputs to VTA promoted active avoidance, long-term aversion, and escape attempts. By testing feeding in the presence of a predator, we observed that ongoing feeding was decreased, and that this predator-induced decrease in feeding was abolished by photoinhibition of the LH-glutamatergic inputs to VTA. By VTA specific neuronal ablation, we established that predator-induced decreases in feeding were mediated by VTA-glutamatergic neurons but not by dopamine or GABA neurons. Thus, we provided evidence for an unanticipated neuronal circuitry between LH-glutamatergic inputs to VTA-glutamatergic neurons that plays a role in prioritizing escape, and in the switch from feeding to escape in mice.

Mutations in autism spectrum disorder (ASD) risk genes disrupt neural network dynamics that ultimately lead to abnormal behavior. To understand how ASD-risk genes influence neural circuit computation during behavior, we analyzed the hippocampal network by performing large-scale cellular calcium imaging from hundreds of individual CA1 neurons simultaneously in transgenic mice with total knockout of the X-linked ASD-risk gene NEXMIF (neurite extension and migration factor). As NEXMIF knockout in mice led to profound learning and memory deficits, we examined the CA1 network during voluntary locomotion, a fundamental component of spatial memory. We found that NEXMIF knockout does not alter the overall excitability of individual neurons but exaggerates movement-related neuronal responses. To quantify network functional connectivity changes, we applied closeness centrality analysis from graph theory to our large-scale calcium imaging datasets, in addition to using the conventional pairwise correlation analysis. Closeness centrality analysis considers both the number of connections and the connection strength between neurons within a network. We found that in wild-type mice the CA1 network desynchronizes during locomotion, consistent with increased network information coding during active behavior. Upon NEXMIF knockout, CA1 network is over-synchronized regardless of behavioral state and fails to desynchronize during locomotion, highlighting how perturbations in ASD-implicated genes create abnormal network synchronization that could contribute to ASD-related behaviors.

Progress in understanding brain–viscera interoceptive signaling is hindered by a dearth of implantable devices suitable for probing both brain and peripheral organ neurophysiology during behavior. Here we describe multifunctional neural interfaces that combine the scalability and mechanical versatility of thermally drawn polymer-based fibers with the sophistication of microelectronic chips for organs as diverse as the brain and the gut. Our approach uses meters-long continuous fibers that can integrate light sources, electrodes, thermal sensors and microfluidic channels in a miniature footprint. Paired with custom-fabricated control modules, the fibers wirelessly deliver light for optogenetics and transfer data for physiological recording. We validate this technology by modulating the mesolimbic reward pathway in the mouse brain. We then apply the fibers in the anatomically challenging intestinal lumen and demonstrate wireless control of sensory epithelial cells that guide feeding behaviors. Finally, we show that optogenetic stimulation of vagal afferents from the intestinal lumen is sufficient to evoke a reward phenotype in untethered mice.

Absence seizures are characterized by brief periods of unconsciousness accompanied by lapses in motor function that can occur hundreds of times throughout the day. Outside of these frequent moments of unconsciousness, approximately a third of people living with the disorder experience treatment-resistant attention impairments. Convergent evidence suggests prefrontal cortex (PFC) dysfunction may underlie attention impairments in affected patients. To examine this, we use a combination of slice physiology, fiber photometry, electrocorticography (ECoG), optogenetics, and behavior in the Scn8a +/- mouse model of absence epilepsy. Attention function was measured using a novel visual attention task where a light cue that varied in duration predicted the location of a food reward. In Scn8a +/- mice, we find altered parvalbumin interneuron (PVIN) output in the medial PFC (mPFC) in vitro and PVIN hypoactivity along with reductions in gamma power during cue presentation in vivo. This was associated with poorer attention performance in Scn8a +/- mice that could be rescued by gamma-frequency optogenetic stimulation of PVINs. This highlights cue-related PVIN activity as an important mechanism for attention and suggests PVINs may represent a therapeutic target for cognitive comorbidities in absence epilepsy.

Excessive fear is a hallmark of anxiety disorders, a major cause of disease burden worldwide. Substantial evidence supports a role of prefrontal cortex-amygdala circuits in the regulation of fear and anxiety, but the molecular mechanisms that regulate their activity remain poorly understood. Here, we show that downregulation of the histone methyltransferase PRDM2 in the dorsomedial prefrontal cortex enhances fear expression by modulating fear memory consolidation. We further show that Prdm2 knock-down (KD) in neurons that project from the dorsomedial prefrontal cortex to the basolateral amygdala (dmPFC-BLA) promotes increased fear expression. Prdm2 KD in the dmPFC-BLA circuit also resulted in increased expression of genes involved in synaptogenesis, suggesting that Prdm2 KD modulates consolidation of conditioned fear by modifying synaptic strength at dmPFC-BLA projection targets. Consistent with an enhanced synaptic efficacy, we found that dmPFC Prdm2 KD increased glutamatergic release probability in the BLA and increased the activity of BLA neurons in response to fear-associated cues. Together, our findings provide a new molecular mechanism for excessive fear responses, wherein PRDM2 modulates the dmPFC -BLA circuit through specific transcriptomic changes.

Intracortical microstimulation (ICMS) of the somatosensory cortex (S1) can restore sensory function in patients with paralysis. Studies assessing the stability of ICMS have reported heterogeneous responses across electrodes and over time, potentially hindering the implementation and translatability of these technologies. The foreign body response (FBR) and the encapsulating glial scar have been associated with a decay in chronic performance of implanted electrodes. Moreover, the morphology, intrinsic properties, and function of cells vary across cortical layers, each potentially affecting the sensitivity to ICMS as well as the degree of the FBR across cortical depth. However, layer-by-layer comparisons of the long-term stability of ICMS as well as the extent of the astrocytic glial scar change across cortical layers have not been well explored. Here, we implanted silicon microelectrodes with electrode sites spanning all the layers of S1 in rats. Using a behavioral paradigm, we obtained ICMS detection thresholds from all cortical layers for up to 40 weeks. Our results showed that the sensitivity and long-term performance of ICMS is indeed layer dependent. Overall, detection thresholds decreased during the first 7 weeks post-implantation (WPI). This was followed by a period in which thresholds remained stable or increased depending on the interfacing layer: thresholds in L1 and L6 exhibited the most consistent increases over time, while those in L4 and L5 remained the most stable. Furthermore, histological investigation of the tissue surrounding the electrode showed a biological response of microglia and macrophages which peaked at L1, while the area of the astrocytic glial scar peaked at L2/3. Interestingly, the biological response of these FBR markers is less exacerbated at L4 and L5, suggesting a potential link between the FBR and the long-term stability of ICMS. These findings suggest that interfacing depth can play an important role in the design of chronically stable implantable microelectrodes.