Chronic Stress Alters Spatial Representation and Bursting Patterns of Place Cells in Behaving Mice

Disruption of the Na+/K+-ATPase-purinergic P2X7 receptor complex in microglia promotes stress-induced anxiety

Na+/K+-ATPase (NKA) plays an important role in the central nervous system. However, little is known about its function in the microglia. Here, we found that NKAα1 forms a complex with the purinergic P2X7 receptor (P2X7R), an adenosine 5'-triphosphate (ATP)-gated ion channel, under physiological conditions. Chronic stress or treatment with lipopolysaccharide plus ATP decreased the membrane expression of NKAα1 in microglia, facilitated P2X7R function, and promoted microglia inflammatory activation via activation of the NLRP3 inflammasome. Accordingly, global deletion or conditional deletion of NKAα1 in microglia under chronic stress-induced aggravated anxiety-like behavior and neuronal hyperexcitability. DR5-12D, a monoclonal antibody that stabilizes membrane NKAα1, improved stress-induced anxiety-like behavior and ameliorated neuronal hyperexcitability and neurogenesis deficits in the ventral hippocampus of mice. Our results reveal that NKAα1 limits microglia inflammation and may provide a target for the treatment of stress-related neuroinflammation and diseases.

The medial entorhinal cortex is necessary for the stimulus control over hippocampal place fields by distal, but not proximal, landmarks

A fundamental property of place cells in the hippocampus is the anchoring of their firing fields to salient landmarks within the environment. However, it is unclear how such information reaches the hippocampus. In the current experiment, we tested the hypothesis that the stimulus control exerted by distal visual landmarks requires input from the medial entorhinal cortex (MEC). Place cells were recorded from mice with ibotenic acid lesions of the MEC (n = 7) and from sham-lesioned mice (n = 6) following 90° rotations of either distal landmarks or proximal cues in a cue- controlled environment. We found that lesions of the MEC impaired the anchoring of place fields to distal landmarks, but not proximal cues. We also observed that, relative to sham-lesioned mice, place cells in animals with MEC lesions exhibited significantly reduced spatial information and increased sparsity. These results support the view that distal landmark information reaches the hippocampus via the MEC, but that proximal cue information can do so via an alternative neural pathway.

Neurocognitive effects of stress: a metaparadigm perspective

Stressful experiences, both physical and psychological, that are overwhelming (i.e., inescapable and unpredictable), can measurably affect subsequent neuronal properties and cognitive functioning of the hippocampus. At the cellular level, stress has been shown to alter hippocampal synaptic plasticity, spike and local field potential activity, dendritic morphology, neurogenesis, and neurodegeneration. At the behavioral level, stress has been found to impair learning and memory for declarative (or explicit) tasks that are based on cognition, such as verbal recall memory in humans and spatial memory in rodents, while facilitating those that are based on emotion, such as differential fear conditioning in humans and contextual fear conditioning in rodents. These vertically related alterations in the hippocampus, procedurally observed after subjects have undergone stress, are generally believed to be mediated by recurrently elevated circulating hypothalamic-pituitary-adrenal (HPA) axis effector hormones, glucocorticoids, directly acting on hippocampal neurons densely populated with corticosteroid receptors. The main purposes of this review are to (i) provide a synopsis of the neurocognitive effects of stress in a historical context that led to the contemporary HPA axis dogma of basic and translational stress research, (ii) critically reappraise the necessity and sufficiency of the glucocorticoid hypothesis of stress, and (iii) suggest an alternative metaparadigm approach to monitor and manipulate the progression of stress effects at the neural coding level. Real-time analyses can reveal neural activity markers of stress in the hippocampus that can be used to extrapolate neurocognitive effects across a range of stress paradigms (i.e., resolve scaling and dichotomous memory effects issues) and understand individual differences, thereby providing a novel neurophysiological scaffold for advancing future stress research.

Biological embedding of early trauma: the role of higher prefrontal synaptic strength

Background: Early trauma predicts poor psychological and physical health. Glutamatergic synaptic processes offer one avenue for understanding this relationship, given glutamate's abundance and involvement in reward and stress sensitivity, emotion, and learning. Trauma-induced glutamatergic excitotoxicity may alter neuroplasticity and approach/avoidance tendencies, increasing risk for psychiatric disorders. Studies examine upstream or downstream effects instead of glutamatergic synaptic processes in vivo, limiting understanding of how trauma affects the brain.Objective: In a pilot study using a previously published data set, we examine associations between early trauma and a proposed measure of synaptic strength in vivo in one of the largest human samples to undergo Carbon-13 (13C MRS) magnetic resonance spectroscopy. Participants were 18 healthy controls and 16 patients with PTSD (male and female).Method: Energy per cycle (EPC), which represents the ratio of neuronal oxidative energy production to glutamate neurotransmitter cycling, was generated as a putative measure of glutamatergic synaptic strength.Results: Results revealed that early trauma was positively correlated with EPC in individuals with PTSD, but not in healthy controls. Increased synaptic strength was associated with reduced behavioural inhibition, and EPC showed stronger associations between reward responsivity and early trauma for those with higher EPC.Conclusion: In the largest known human sample to undergo 13C MRS, we show that early trauma is positively correlated with EPC, a direct measure of synaptic strength. Our study findings have implications for pharmacological treatments thought to impact synaptic plasticity, such as ketamine and psilocybin.

Forebrain Glucocorticoid Receptor Overexpression Alters Behavioral Encoding of Hippocampal CA1 Pyramidal Cells in Mice

Glucocorticoid signaling influences hippocampal-dependent behavior and vulnerability to stress-related neuropsychiatric disorders. In mice, lifelong overexpression of glucocorticoid receptor (GR) in forebrain excitatory neurons altered exploratory behavior, cognition, and dorsal hippocampal gene expression in adulthood, but whether GR overexpression alters the information encoded by hippocampal neurons is not known. We performed in vivo microendoscopic calcium imaging of 1359 dorsal CA1 pyramidal cells in freely behaving male and female wild-type (WT) and GR-overexpressing (GRov) mice during exploration of a novel open field, where most CA1 neurons are expected to respond to center location and mobility. Most neurons showed sensitivity to center location and/or mobility based on single-neuron calcium amplitude and event rate, but these sensitivity patterns differed between genotypes. GRov neurons were more likely than WT neurons to display center sensitivity and less likely to display mobility sensitivity. More than one-third of these responsive GRov neurons were sensitive only to center location and not mobility, while uniquely center-sensitive neurons were rare in WT. Most center-sensitive neurons exhibited anticipatory activity, suggesting they could drive behavior. We conclude that, compared with wild-type, dorsal CA1 pyramidal cells in GRov mice preferentially respond to center location rather than mobility in a novel open field. Such changes in the information encoded by individual hippocampal neurons in an aversive environment could underlie changes in stress vulnerability because of genetic or epigenetic variations in glucocorticoid receptor signaling.

Repeated stress exposure leads to structural synaptic instability prior to disorganization of hippocampal coding and impairments in learning

Stress exposure impairs brain structure and function, resulting in cognitive deficits and increased risk for psychiatric disorders such as depression, schizophrenia, anxiety and post-traumatic stress disorder. In particular, stress exposure affects function and structure of hippocampal CA1 leading to impairments in episodic memory. Here, we applied longitudinal deep-brain optical imaging to investigate the link between changes in activity patterns and structural plasticity of dorsal CA1 pyramidal neurons and hippocampal-dependent learning and memory in mice exposed to stress. We found that several days of repeated stress led to a substantial increase in neuronal activity followed by disruption of the temporal structure of this activity and spatial coding. We then tracked dynamics of structural excitatory connectivity as a potential underlying cause of the changes in activity induced by repeated stress. We thus discovered that exposure to repeated stress leads to an immediate decrease in spinogenesis followed by decrease in spine stability. By comparison, acute stress led to stabilization of the spines born in temporal proximity to the stressful event. Importantly, the temporal relationship between changes in activity levels, structural connectivity and activity patterns, suggests that loss of structural connectivity mediates the transition between increased activity and impairment of temporal organization and spatial information content in dorsal CA1 upon repeated stress exposure.

Astrocytes Render Memory Flexible by Releasing D-Serine and Regulating NMDA Receptor Tone in the Hippocampus

BACKGROUND

NMDA receptor (NMDAR) hypofunction has been implicated in several psychiatric disorders with impairment of cognitive flexibility. However, the molecular mechanism of how NMDAR hypofunction with decreased NMDAR tone causes the impairment of cognitive flexibility has been minimally understood. Furthermore, it has been unclear whether hippocampal astrocytes regulate NMDAR tone and cognitive flexibility.

METHODS

We employed cell type-specific genetic manipulations, ex vivo electrophysiological recordings, sniffer patch recordings, cutting-edge biosensor for norepinephrine, and behavioral assays to investigate whether astrocytes can regulate NMDAR tone by releasing D-serine and glutamate. Subsequently, we further investigated the role of NMDAR tone in heterosynaptic long-term depression, metaplasticity, and cognitive flexibility.

RESULTS

We found that hippocampal astrocytes regulate NMDAR tone via BEST1-mediated corelease of D-serine and glutamate. Best1 knockout mice exhibited reduced NMDAR tone and impairments of homosynaptic and α₁ adrenergic receptor-dependent heterosynaptic long-term depression, which leads to defects in metaplasticity and cognitive flexibility. These impairments in Best1 knockout mice can be rescued by hippocampal astrocyte-specific BEST1 expression or enhanced NMDAR tone through D-serine supplement. D-serine injection in Best1 knockout mice during initial learning rescues subsequent reversal learning.

CONCLUSIONS

These findings indicate that NMDAR tone during initial learning is important for subsequent learning, and hippocampal NMDAR tone regulated by astrocytic BEST1 is critical for heterosynaptic long-term depression, metaplasticity, and cognitive flexibility.

The impact of stress on the hippocampal spatial code

Hippocampal function is severely compromised by prolonged, uncontrollable stress. However, how stress alters neural representations of our surroundings and events that occur within them remains less clear. We review hippocampal place cell studies that examine how spatial coding is affected by acute and chronic stress, as well as by stress accompanying fear conditioning. Emerging data suggest that chronic stress disrupts the acuity and specificity of CA1 spatial coding, both in familiar and novel contexts, and alters hippocampal oscillations. By contrast, acute stress may have a facilitatory impact on spatial representations. These findings encourage a fresh look at the documented stress-induced changes in hippocampal anatomy and in vitro excitability, and offer a new perspective on the links between stress and memory.

Stress enhances hippocampal neuronal synchrony and alters ripple-spike interaction

Adverse effects of chronic stress include anxiety, depression, and memory deficits. Some of these stress-induced behavioural deficits are mediated by impaired hippocampal function. Much of our current understanding about how stress affects the hippocampus has been derived from post-mortem analyses of brain slices at fixed time points. Consequently, neural signatures of an ongoing stressful experiences in the intact brain of awake animals and their links to later hippocampal dysfunction remain poorly understood. Further, no information is available on the impact of stress on sharp-wave ripples (SPW-Rs), high frequency oscillation transients crucial for memory consolidation. Here, we used in vivo tetrode recordings to analyze the dynamic impact of 10 days of immobilization stress on neural activity in area CA1 of mice. While there was a net decrease in pyramidal cell activity in stressed animals, a greater fraction of CA1 spikes occurred specifically during sharp-wave ripples, resulting in an increase in neuronal synchrony. After repeated stress some of these alterations were visible during rest even in the absence of stress. These findings offer new insights into stress-induced changes in ripple-spike interactions and mechanisms through which chronic stress may interfere with subsequent information processing.

Impaired Cognitive Flexibility Induced by Chronic Cerebral Hypoperfusion in the 5XFAD Transgenic Mouse Model of Mixed Dementia

Cerebrovascular lesions are widely prevalent in patients with Alzheimer’s disease (AD), but their relationship to the pathophysiology of AD remains poorly understood. An improved understanding of the interaction of cerebrovascular damage with AD is crucial for the development of therapeutic approaches. Herein, we investigated the effects of chronic cerebral hypoperfusion (CCH) in a 5XFAD transgenic (Tg) mouse model of AD. We established CCH conditions in both Tg and non-Tg mice by inducing unilateral common carotid artery occlusion (UCCAO). Cognitive performance in mice was evaluated, and their brain tissue was examined for amyloid-beta (Aβ) pathology to elucidate possible mechanisms. We found that UCCAO-operated Tg mice showed impaired cognitive flexibility in the reversal phase of the hidden-platform water maze task compared to sham-operated Tg mice. Interestingly, UCCAO-operated Tg mice used fewer spatial cognitive strategies than sham-operated Tg mice during reversal learning. These cognitive deficits were accompanied by increased Aβ plaque burden and Aβ42 levels in the hippocampus and prefrontal cortex, 2 regions that play essential roles in the regulation of cognitive flexibility. Furthermore, changes in cognitive flexibility are strongly correlated with the expression levels of enzymes related to Aβ clearance, such as neprilysin and insulin-degrading enzymes. These findings suggest that, in 5XFAD mice, impaired cognitive flexibility is related to CCH, and that Aβ clearance might be involved in this process.

Characterization of Comorbid Posttraumatic Stress Disorder and Major Depressive Disorder Using Ketamine as an Experimental Medicine Probe

Comorbid posttraumatic stress disorder and major depressive disorder (PTSD + MDD) is the most common pathological response to trauma, yet despite their synergistic detriment to health, knowledge regarding the neurobiological mechanism underlying PTSD + MDD is extremely limited. This study proposes a novel model of PTSD + MDD that is built on biological systems shown to underlay PTSD + MDD and takes advantage of ketamine’s unique suitability to probe PTSD + MDD due to its rescue of stress-related neuroplasticity deficits. The central hypothesis is that changes in PTSD + MDD clinical symptoms are associated with functional connectivity changes and cognitive dysfunction and that ketamine infusions improve clinical symptoms by correction of functional connectivity changes and improvement in cognition. Participants with PTSD + MDD (n = 42) will be randomized to receive a series of six ketamine infusions or saline-placebo over three weeks. Pre/post-measures will include: (1) neuroimaging; (2) cognitive functioning task performance; and (3) PTSD, MDD, and rumination self-report measures. These measures will also be collected once in a trauma-exposed group including PTSD-only (n = 10), trauma-exposed-MDD (TE-MDD; n = 10), and healthy controls (HC, n = 21). Successful completion of the study will strongly support the concept of a biologically-based model of PTSD + MDD. The results will (1) identify functional imaging signatures of the mechanisms underpinning pathological responses to trauma, (2) shift focus from mono-diagnostic silos to unified biological and behavioral disease processes and, thus, (3) inform interventions to correct dysregulation of PTSD + MDD symptom clusters thereby supporting more precise treatments and better outcomes.

Links Between Human and Animal Models of Trauma and Psychosis: A Narrative Review

Traumatic experiences during development are associated with an increased risk of developing psychosis. Individuals with psychosis also report a higher rate of past trauma than healthy control subjects and worse outcomes than those who do not have these experiences. It is thought that traumatic experiences negatively impact specific neurobiological processes to confer this increased risk, and that systems affected by trauma are similarly changed in individuals with psychosis. Examining animal models of psychosis and the shared neurobiological changes in response to stressors can offer valuable insight into biological mechanisms that mediate symptoms and targets for intervention. This targeted review highlights a subset of models of psychosis across humans and animals, examines the similarities with the brain's response to stress and traumatic events, and discusses how these models may interact. Suggestions for future research are described.

Cognitive dysfunction in mice lacking proper glucocorticoid receptor dimerization

Stress is a major risk factor for depression and anxiety. One of the effects of stress is the (over-) activation of the hypothalamic-pituitary-adrenal (HPA) axis and the release of stress hormones such as glucocorticoids (GCs). Chronically increased stress hormone levels have been shown to have detrimental effects on neuronal networks by inhibiting neurotrophic processes particularly in the hippocampus proper. Centrally, GCs modulate metabolic as well as behavioural processes by activating two classes of corticoid receptors, high-affinity mineralocorticoid receptors (MR) and low-affinity glucocorticoid receptors (GR). Upon activation, GR can modulate gene transcription either as a monomeric protein, or as a dimer interacting directly with DNA. GR can also modulate cellular processes via non-genomic mechanisms, for example via a GPCR-protein interaction. We evaluated the behavioral phenotype in mice with a targeted mutation in the GR in a FVB/NJ background. In GRdim/dim mice, GR proteins form poor homodimers, while the GR monomer remains intact. We evaluated the effect of poor GR dimerization on hippocampus-dependent cognition as well as on exploration and emotional behavior under baseline and chronically increased stress hormone levels. We found that GRdim/dim mice did not behave differently from GRwt/wt littermates under baseline conditions. However, after chronic elevation of stress hormone levels, GRdim/dim mice displayed a significant impairment in hippocampus-dependent memory compared to GRwt/wt mice, which correlated with differential expression of hippocampal Bdnf/TrkB and Fkbp5.

Impaired Cognitive Performance in Endothelial Nitric Oxide Synthase Knockout Mice After Ischemic Stroke: A Pilot Study

OBJECTIVES

Cognitive dysfunction and dementia are common following ischemic stroke. Endothelial nitric oxide synthase (eNOS) has been found to play an important role in neurologic function and cognition. The purpose of the present study was to assess the specific role of eNOS in cognitive performance after stroke.

DESIGN

Male wild-type and mice lacking eNOS (eNOS) underwent middle cerebral artery occlusion or sham-surgery. Primary outcomes were repeated measures of neurologic score, limb asymmetry, sensory/motor function, and spatial memory/learning assessed at intervals up to 28 days postsurgery. Group differences in brain microglia activation and infiltration and levels of interferon-gamma were examined.

RESULTS

There was no genotype × surgery interaction effect on the pattern of change in neurologic score, limb asymmetry, or sensory motor function across the 28 days postsurgery. In the Morris water maze, eNOS-/- middle cerebral artery occlusion mice displayed learning and memory deficits not evident in wild-type middle cerebral artery occlusion mice. Poorer spatial memory and learning in eNOS-/- middle cerebral artery occlusion mice was associated with a reduction in the number of activated microglia in the striatum on the lesion side and decreased brain tissue levels of interferon-gamma.

CONCLUSIONS

This study's data support a role for eNOS in cognitive performance after stroke. This finding may lead to the development of novel interventions to treat poststroke cognitive deficits.

In vivo Calcium Imaging Reveals That Cortisol Treatment Reduces the Number of Place Cells in Thy1-GCaMP6f Transgenic Mice

The hippocampus, a structure essential for spatial navigation and memory undergoes anatomical and functional changes during chronic stress. Here, we investigate the effects of chronic stress on the ability of place cells to encode the neural representation of a linear track. To model physiological conditions of chronic stress on hippocampal function, transgenic mice expressing the genetically encoded calcium indicator GCaMP6f in CA1 pyramidal neurons were chronically administered with 40 μg/ml of cortisol for 8 weeks. Cortisol-treated mice exhibited symptoms typically observed during chronic stress, including diminished reward seeking behavior and reduced adrenal gland and spleen weights. In vivo imaging of hippocampal cellular activity during linear track running behavior revealed a reduced number of cells that could be recruited to encode spatial position, despite an unchanged overall number of active cells, in cortisol-treated mice. The properties of the remaining place cells that could be recruited to encode spatial information, however, was unperturbed. Bayesian decoders trained to estimate the mouse’s position on the track using single neuron activity data demonstrated reduced performance in a cue richness-dependent fashion in cortisol-treated animals. The performance of decoders utilizing data from the entire neuronal ensemble was unaffected by cortisol treatment. Finally, to test the hypothesis that an antidepressant drug could prevent the effects of cortisol, we orally administered a group of mice with 10 mg/kg citalopram during cortisol administration. Citalopram prevented the cortisol-induced decrease in single-neuron decoder performance but failed to significantly prevent anhedonia and the cortisol-induced reduction in the proportion place cells. The dysfunction observed at the single-neuron level indicates that chronic stress may impair the ability of the hippocampus to encode individual neural representations of the mouse’s spatial position, a function pivotal to forming an accurate navigational map of the mouse’s external environment; however, the hippocampal ensemble as a whole is resilient to any cortisol-induced insults to single neuronal place cell function on the linear track.

The Ventral Midline Thalamus Mediates Hippocampal Spatial Information Processes upon Spatial Cue Changes

The ventral midline thalamus, consisting of the reuniens and rhomboid nuclei (RE/Rh), is a thalamic structure interconnected with the limbic systems including the hippocampus. Recently, many studies have revealed that this structure plays distinctive roles in spatial learning and memory in collaboration with hippocampal functions. However, what aspects of spatial information process are influenced by the RE/Rh is not clearly known. To elucidate the roles of RE/Rh in spatial information processing and its effects on hippocampal activity, specifically with the manipulation of spatial contents, we measured hippocampal-dependent spatial memory performance and hippocampal place cell activities after RE/Rh lesion using male C57BL/6J × 129/SvJae hybrid mice. We found that the lesion altered the behavioral aptitude in recognizing locational changes of an object. Furthermore, CA1 place cells in the lesion group showed different spatial representation patterns in recognizing the environment with cue locational changes compared with the control group. Interestingly, the patterns of CA1 place cells in recognizing the same environment previously visited were not disrupted in the lesion group compared with the control group. These findings demonstrate that the ventral midline thalamus (RE/Rh) is important in recognizing the spatial relationships, especially when spatial rearrangement of cue position was introduced.SIGNIFICANCE STATEMENT The ventral midline thalamic nuclei (reuniens and rhomboid) interact with the hippocampus to influence various cognitive functions requiring spatial memories, yet what aspects of spatial information process are influenced by these nuclei is not clearly known. Here, we reveal that these nuclei play a crucial role in modulating hippocampal properties only with locational rearrangement of cues, not with the familiar arrangement. These nuclei are distinctively involved in cue-dependent spatial information processes of CA1 place cells. In particular, we suggest that these nuclei modulate spatial information processing on discrete components, especially when the spatial cue relationship is modified.

Unpredictable chronic mild stress differentially impairs social and contextual discrimination learning in two inbred mouse strains

Alterations in the social and cognitive domain are considered important indicators for increased disability in many stress-related disorders. Similar impairments have been observed in rodents chronically exposed to stress, mimicking potential endophenotypes of stress-related psychopathologies such as major depression disorder (MDD), anxiety, conduct disorder, and posttraumatic stress disorder (PTSD). Data from numerous studies suggest that deficient plasticity mechanisms in hippocampus (HC) and prefrontal cortex (PFC) might underlie these social and cognitive deficits. Specifically, stress-induced deficiencies in neural plasticity have been associated with a hypodopaminergic state and reduced neural plasticity persistence. Here we assessed the effects of unpredictable chronic mild stress (UCMS) on exploratory, social and cognitive behavior of females of two inbred mouse strains (C57BL/6J and DBA/2J) that differ in their dopaminergic profile. Exposure to chronic stress resulted in impaired circadian rhythmicity, sociability and social cognition in both inbred strains, but differentially affected activity patterns and contextual discrimination performance. These stress-induced behavioral impairments were accompanied by reduced expression levels of brain derived neurotrophic factor (BDNF) in the prefrontal cortex. The strain-specific cognitive impairment was coexistent with enhanced plasma corticosterone levels and reduced expression of genes related to dopamine signaling in hippocampus. These results underline the importance of assessing different strains with multiple test batteries to elucidate the neural and genetic basis of social and cognitive impairments related to chronic stress.

Synaptic Loss and the Pathophysiology of PTSD: Implications for Ketamine as a Prototype Novel Therapeutic

PURPOSE OF REVIEW

Studies of the neurobiology and treatment of PTSD have highlighted many aspects of the pathophysiology of this disorder that might be relevant to treatment. The purpose of this review is to highlight the potential clinical importance of an often-neglected consequence of stress models in animals that may be relevant to PTSD: the stress-related loss of synaptic connectivity.

RECENT FINDINGS

Here, we will briefly review evidence that PTSD might be a "synaptic disconnection syndrome" and highlight the importance of this perspective for the emerging therapeutic application of ketamine as a potential rapid-acting treatment for this disorder that may work, in part, by restoring synaptic connectivity. Synaptic disconnection may contribute to the profile of PTSD symptoms that may be targeted by novel pharmacotherapeutics.

Conditional Knockout of Cav2.1 Disrupts the Accuracy of Spatial Recognition of CA1 Place Cells and Spatial/Contextual Recognition Behavior

Hippocampal pyramidal neurons play an essential role in processing spatial information as implicated with its place-dependent firing. Although, previous slice physiology studies have reported that voltage gated calcium channels contribute to spike shapes and corresponding firing rate in the hippocampus, the roles of P/Q type calcium channels (Cav2.1) underlying neural activity in behaving mice have not been well-investigated. To determine physiological and behavioral roles of Cav2.1, we conducted place cell recordings in CA1 and hippocampus dependent learning/memory tasks using mice lacking Cav2.1 in hippocampal pyramidal neurons under CamK2α-Cre recombinase expression. Results suggested that impairments shown in behavioral tasks requiring spatial and contextual information processing were statistically significant while general neurological behaviors did not differ between groups. In particular, deficits were more profound in recognition than in acquisition. Furthermore, place cell recordings also revealed that the ability to recollect spatial representation on re-visit in the conditional knockout was also altered in terms of the cue recognition while the capability of a place cell to encode a place was intact compared to the control group. Interestingly, CA1 pyramidal neurons of conditional knockout mice showed reduced burst frequency as well as abnormal temporal patterns of burst spiking. These results provide potential evidence that Cav2.1 in hippocampal pyramidal cells modulates temporal integration of bursts, which, in turn, might influence the recognition of place field and consequently disrupt spatial recognition ability.