Observational fear (OF) is the ability to vicariously experience and learn from another's fearful situation, enabling adaptive responses crucial for survival. It has been shown that the anterior cingulate cortex (ACC) an...Observational fear (OF) is the ability to vicariously experience and learn from another's fearful situation, enabling adaptive responses crucial for survival. It has been shown that the anterior cingulate cortex (ACC) and basolateral amygdala (BLA) are crucial for OF. A subset of neurons in the ACC is activated when observing aversive events in the demonstrator, which elicits OF. However, the neural circuit mechanisms underlying the expression of OF-related activity in the ACC remain unexplored. Previous studies have shown that the mediodorsal thalamus (MD) is crucial for OF, and MD neurons project to the ACC. Therefore, we hypothesize that the projection from MD to ACC may facilitate the OF-related activity in the ACC. By utilizing in vivo calcium imaging combined with the optogenetic terminal inhibition of MD-ACC pathway, we found that a subset of ACC neurons was activated when observing demonstrator's fearful situation in male mice. Furthermore, the optogenetic inhibition of the MD-ACC projection during the demonstrator's aversive moments significantly suppressed the OF-related activity in the ACC. Our data suggests that the MD-ACC projection plays a role in OF-related activity in ACC neurons.
Cardiac arrest (CA) is one of the most common illnesses worldwide. Post-CA brain injury (PCABI) is a major cause of death and poor recovery in CA patients and the current CA treatments are not very effective. The microbi...Cardiac arrest (CA) is one of the most common illnesses worldwide. Post-CA brain injury (PCABI) is a major cause of death and poor recovery in CA patients and the current CA treatments are not very effective. The microbiome-gut-brain axis has been found to significantly affect brain ischemia injury. Furthermore, in ischemic stroke patients, short-chain fatty acids (SCFA), especially sodium butyrate (SB), have been observed to promote neuroprotective effects by modulating inflammatory response and microglial polarization in the cortex. However, the precise mechanism of SB on CA-induced injury remains elusive. Therefore, this research study established an oxygen-glucose deprivation and reoxygenation (OGD/R) model using BV-2 microglial and HT22 cells to simulate cerebral ischemia/reperfusion injury in vitro and a potassium chloride-induced CA mouse model to mimic CA in vivo. The data revealed that SB markedly improved neurological scores and reduced neuronal death and apoptosis. Moreover, it reduced M1 microglia and neuroinflammation in CA mice. In addition, SB increased intestinal integrity and alleviated systemic inflammation. The 16S rDNA sequencing analysis indicated that SB intervention mitigated CA-induced gut microbiota dysbiosis and SCFA depletion. It was also observed that CA mice's brain and OGD/R-exposed BV2 cells had substantially increased levels of MyD88, phosphorylated NF-κB p65, and TLR4 proteins, which were reduced after SB treatment. In summary, this study revealed that SB can protect against cerebral ischemia-reperfusion injury by controlling microglia polarization and microbiome-gut-brain axis to inhibit brain inflammation via the TLR4/MyD88/NF-κB pathway.
Angiogenesis in the ischemic penumbra compensates for microcirculatory dysfunction and promotes neuronal plasticity after stroke. However, the current understanding may be highly biased because the contribution of veins...Angiogenesis in the ischemic penumbra compensates for microcirculatory dysfunction and promotes neuronal plasticity after stroke. However, the current understanding may be highly biased because the contribution of veins to angiogenesis has been overlooked. This study revealed that the remodeling processes of veins differ from those of arteries after ischemia. Ligation of the right jugular vein increased the infarct volume, decreased cerebral blood flow and impaired long-term functional restoration after stroke. RNA-seq analysis revealed significant upregulation of the expression of genes associated with angiogenesis in the infarct core during the recovery period. By using gelatin ink-alkaline phosphatase-oil red O (GIAO) staining, we found that venogenesis, the process of creating new veins, was the predominant angiogenic event in the infarct core. Macrophage infiltration and transformation are closely associated with venogenesis in the infarct core. However, depletion of macrophages in the circulation by clodronate liposomes in the acute phase inhibited the proliferation of endothelial progenitor cells and decreased the vascular density in the infarct core. This study demonstrated that dynamic vein remodeling is crucial for cerebral ischemic damage and subsequent neuronal restoration. Angiogenesis occurs in the infarct core during the recovery period, promotes the absorption of necrotic tissue and facilitates functional recovery after stroke.
Neuronal autophagy is essential for maintaining protein and organelle turnover, thereby safeguarding neuronal health. LC3, a central autophagy protein, exists in lipidated (LC3-II) and non-lipidated (LC3-I) forms, both c...Neuronal autophagy is essential for maintaining protein and organelle turnover, thereby safeguarding neuronal health. LC3, a central autophagy protein, exists in lipidated (LC3-II) and non-lipidated (LC3-I) forms, both critical for neurons due to their sensitivity to metabolic and proteostatic stress. To elucidate the specific roles of membrane-anchored LC3A/B in post-mitotic neurons, we engineered deconjugases with enhanced selectivity for lipidated LC3. By modifying LC3-interacting regions (LIRs) at the deconjugase termini, we significantly improved targeting specificity toward LC3A/B. Deconjugases with N-terminal LIR modifications reduced LC3A/B-associated autophagosomes, highlighting the importance of LIR positioning for specificity. Sequential N-terminal LIR arrangements further refined LC3A/B targeting without affecting GABARAP-associated autophagosomes. Moreover, reducing the hydrophobicity of the α3 helix to limit membrane residence time further improved selectivity. These targeted modifications demonstrate the potential of customized deconjugases to dissect and modulate specific autophagic pathways in neurons, paving the way for novel therapeutic strategies against neurodegenerative diseases associated with autophagy dysregulation.
The microenvironment of the central nervous system is highly complex and plays a crucial role in maintaining the function of neurons, which influences Alzheimer's disease (AD) progression. The pH value of the brain is a...The microenvironment of the central nervous system is highly complex and plays a crucial role in maintaining the function of neurons, which influences Alzheimer's disease (AD) progression. The pH value of the brain is a critical aspect of the brain microenvironment in regulating various physiological processes. However, the specific mechanisms and role of this mechanism are not yet fully understood. To better understand the relationship between brain pH and AD, we analyzed the brain pH of the frontal lobe and AD pathology scores in postmortem brain samples from 368 donors from the National Human Brain Bank for Development and Function, 96 of whom were diagnosed with AD pathology. Analysis revealed a significant decrease in brain pH in AD patients, which was strongly correlated with β-amyloid plaques and phosphorylated tau proteins. Here, we elucidated the differential protein expression level of CD68-positive microglia between control and AD groups (t = 3.198, df = 20, P = 0.0045), and its protein expression level was correlated negatively with the brain pH value (F = 26.93, p = 0.0006). Our findings revealed that increased activation of CD68-positive microglia and disrupted lysosomal homeostasis in the pathological brain tissue of individuals with AD may lead to a decrease in brain pH.
Brain regions drive multiple physiological functions through specific gene expression patterns that adapt to environmental influences, drug treatments and disease conditions. To generate a detailed atlas of the brain tra...Brain regions drive multiple physiological functions through specific gene expression patterns that adapt to environmental influences, drug treatments and disease conditions. To generate a detailed atlas of the brain transcriptome in the context of diabetes, we carried out RNA sequencing in hypothalamus, hippocampus, brainstem and striatum of the Goto-Kakizaki (GK) rat model of spontaneous type 2 diabetes, which was applied to identify gene transcription adaptation to improved glycemic control following vertical sleeve gastrectomy (VSG) in the GK. Over 19,000 distinct transcripts were detected in the rat brain, including 2794 which were consistently expressed in the four brain regions. Region-specific gene expression was identified in hypothalamus (n = 477), hippocampus (n = 468), brainstem (n = 1173) and striatum (n = 791), resulting in differential regulation of biological processes between regions. Differentially expressed genes between VSG and sham operated rats were only found in the hypothalamus and were predominantly involved in the regulation of endothelium and extracellular matrix. These results provide a detailed atlas of regional gene expression in the diabetic rat brain and suggest that the long term effects of gastrectomy-promoted diabetes remission involve functional changes in the hypothalamus endothelium.
Recent studies have shown that abnormal activity of acid sphingomyelinase (Asm) has been associated with a range of psychiatric disorders including schizophrenia and depression. However, the role of Asm in the regulation...Recent studies have shown that abnormal activity of acid sphingomyelinase (Asm) has been associated with a range of psychiatric disorders including schizophrenia and depression. However, the role of Asm in the regulation of anxiety remains unclear. In the present study, we employed Asm-knockout (Asm KO) mice to investigate the association between Asm and anxiety using behavioral tests, RNA sequencing, q-PCR, immunohistochemical staining, and other methods. The behavioral results showed that Asm KO mice exhibit enhanced anxiety-like behaviors, such as restricted activity, reduced cumulative times in the central area, diminished exploratory interest, delayed latency to feed, through behavioral tests including open field, novelty-suppressed feeding test, elevated plus maze test, ect. Transcriptional profiling combined with bioinformatics analysis revealed the upregulation of Toll-like receptor signaling pathway related gene including Tlr1/2, Ccl3, Ccl4, Ccl5 and Cd86 in Asm KO mice, which was further confirmed by the detection of activated microglia and astrocytes through iba-1 and GFAP immunohistochemical staining. Collectively, our findings uncover a role for Asm in regulating anxiety-like behavior and suggest that it may be essential for the maintenance of emotional stability, indicating its potential as a promising target for treating anxiety disorders.
Delirium is a common complication in elderly surgical patients and is associated with an increased risk of dementia. Although advanced age is a major risk factor, the mechanisms underlying postoperative delirium remain p...Delirium is a common complication in elderly surgical patients and is associated with an increased risk of dementia. Although advanced age is a major risk factor, the mechanisms underlying postoperative delirium remain poorly understood. The glymphatic system, a brain-wide network of perivascular pathways, facilitates cerebrospinal fluid (CSF) flow and supports the clearance of metabolic waste. Impairments in glymphatic function have been observed in aging brains and various neurodegenerative conditions. Using in vivo two-photon imaging, we examined the effects of surgery (laparotomy) on glymphatic function in adult (6 months) and aged (18 months) mice 24 h post-surgery. In adult mice, CSF tracer entry into the brain parenchyma along periarteriolar spaces occurred rapidly following intracisternal tracer injection, with no significant differences between sham and surgery groups. In contrast, aged mice exhibited delayed tracer influx, with further impairments observed in the surgery group compared to sham controls. This glymphatic dysfunction correlated with poorer T-maze performance in aged mice. These findings suggest that surgery exacerbates glymphatic impairment in aging brains, potentially hindering brain waste clearance and contributing to postoperative delirium.
It is unclear how steroid hormones contribute to stroke, and conducting randomized controlled trials to obtain related evidence is challenging. Therefore, Mendelian randomization (MR) technique was employed in this study...It is unclear how steroid hormones contribute to stroke, and conducting randomized controlled trials to obtain related evidence is challenging. Therefore, Mendelian randomization (MR) technique was employed in this study to examine this association. Through genome-wide association meta-analysis, the genetic variants of steroid hormones, including testosterone/17β-estradiol (T/E2) ratio, aldosterone, androstenedione, progesterone, and hydroxyprogesterone, were acquired as instrumental variables. Analysis was done on the impact of these steroid hormones on the risk of stroke subtypes. The T/E2 ratio was associated to an elevated risk of small vessel stroke (SVS) according to the inverse variance weighted approach which was the main MR analytic technique (OR, 1.23, 95% CI: 1.05-1.44, p = 0.009). These findings were solid since no heterogeneity nor horizontal pleiotropy were found. The causal association between T/E2 and SVS was also confirmed in the replication study (p = 0.009). Nevertheless, there was no proof that other steroid hormones increased the risk of stroke. According to this study, T/E2 ratio and SVS are causally related. However, strong evidence for the impact of other steroid hormones on stroke subtypes is still lacking. These findings may be beneficial for developing stroke prevention strategies from steroid hormones levels.
Cognitive processes such as action planning and decision-making require the integration of multiple sensory modalities in response to temporal cues, yet the underlying mechanism is not fully understood. Sleep has a cruci...Cognitive processes such as action planning and decision-making require the integration of multiple sensory modalities in response to temporal cues, yet the underlying mechanism is not fully understood. Sleep has a crucial role for memory consolidation and promoting cognitive flexibility. Our aim is to identify the role of sleep in integrating different modalities to enhance cognitive flexibility and temporal task execution while identifying the specific brain regions that mediate this process. We have designed "Auditory-Gated Patience-to-Action" Task in which mice should process different auditory signals before action execution as well as analyzing the visual inputs for feedback of their action. Mice could learn the task rule and apply it only after sleeping period and could keep the performance constant across sessions. c-fos positive cells showed the involvement of prelimbic cortex (PrL) during task execution. Chemo-genetic inhibition verified that PrL is required for proper signal response and action timing. These findings emphasize that sleep and cortical activity are keys for cognitive flexibility in adapting to different modalities.
Kruppel-like factor 15 (KLF15), a member of the KLF family, is closely involved in many biological processes. However, the mechanism by which KLF15 regulates neural development is still unclear. Considering the complexit...Kruppel-like factor 15 (KLF15), a member of the KLF family, is closely involved in many biological processes. However, the mechanism by which KLF15 regulates neural development is still unclear. Considering the complexity and importance of neural network development, in this study, we investigated the potent regulatory role of KLF15 in neural network development. KLF15 was detected highly expressed in the cerebellum and enriched in Purkinje cells, with a significant increase in KLF15 expression between 15 and 20 days of neural development. Knockdown of KLF15 led to loss of Purkinje cells and impaired motility in mice. Therefore, our study aims to elucidate the relationship between KLF15 and Purkinje cells in mice, may provide a new research idea for the developmental mechanism of the mouse cerebellum.
Recent research has highlighted widespread dysregulation of alternative polyadenylation in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP). Here, we identify sig...Recent research has highlighted widespread dysregulation of alternative polyadenylation in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP). Here, we identify significant disruptions to 3` UTR polyadenylation in the ALS/FTLD-TDP mouse model rNLS8 that correlate with changes in gene expression and protein levels through the re-analysis of published RNA sequencing and proteomic data. A subset of these changes are shared with TDP-43 knock-down mice suggesting depletion of endogenous mouse TDP-43 is a contributor to polyadenylation dysfunction in rNLS8 mice. Some conservation exists between alternative polyadenylation in rNLS8 mice and human disease models including in disease relevant genes and biological pathways. Together, these findings support both TDP-43 loss and toxic gain-of-function phenotypes as contributors to the neurodegeneration in rNLS8 mice, nominating its continued utility as a preclinical model for investigating mechanisms of neurodegeneration in ALS/FTLD-TDP.
OBJECTIVE: Cerebral ischemia-reperfusion injury (CIRI) is a major obstacle to neurological recovery after clinical treatment of ischemic stroke. The aim of this study was to investigate the molecular mechanism of Nek6 al...OBJECTIVE: Cerebral ischemia-reperfusion injury (CIRI) is a major obstacle to neurological recovery after clinical treatment of ischemic stroke. The aim of this study was to investigate the molecular mechanism of Nek6 alleviating CIRI through autophagy after cerebral ischemia. MATERIALS AND METHODS: A mouse model of CIRI was constructed by middle cerebral artery occlusion (MCAO). TUNEL staining was used to observe the apoptosis of neuronal cells. The oxygen glucose deprivation/reoxygenation (OGD/R) model was established by hypoxia and reoxygenation. The cell apoptosis and activity was detected. Western blot was performed to detect the expression of autophagy-related proteins, protein kinase B (Akt)/mammalian target of rapamycin (mTOR) and adenosine 5'-monophosphate-activated protein kinase (AMPK)/mTOR signaling pathway-related proteins. Cellular autophagy flux was observed by fluorometric method. NIMA-related kinase 6 (Nek6) mRNA stability was detected by actinomycin D treatment. Methylation RNA immunoprecipitation technique was used to detect Nek6 methylation level. RESULTS: Nek6 expression was increased in both MCAO and OGD/R models. Overexpression of Nek6 in OGD/R inhibited apoptosis, decreased LC3II and Beclin-1 expression, increased p62 expression, and occurred lysosome dysfunction. Interference with Nek6 has opposite results. Nek6 overexpression promoted p-Akt and p-mTOR protein expressions, inhibited p-AMPK and p-UNC-51-like kinase 1 protein expressions and cell apoptosis, while LY294002, Rapamycin or RSVA405 treatment reversed this effect. Abnormal methyltransferase·like protein 3 (METTL3) expression in CIRI enhanced m6A modification and promoted Nek6 expression level. CONCLUSION: This study confirmed that Nek6 regulates autophagy and alleviates CIRI through the mTOR signaling pathway, which provides a novel therapeutic strategy for patients with ischemic stroke in the future.
Research on serotonin reveals a lack of consensus regarding its role in brain volume, especially concerning biomarkers linked to neurogenesis and neuroplasticity, such as ciliary neurotrophic factor (CNTF), fibroblast gr...Research on serotonin reveals a lack of consensus regarding its role in brain volume, especially concerning biomarkers linked to neurogenesis and neuroplasticity, such as ciliary neurotrophic factor (CNTF), fibroblast growth factor 4 (FGF-4), bone morphogenetic protein 6 (BMP-6), and matrix metalloproteinase-1 (MMP-1) in Alzheimer's disease (AD). This study aimed to investigate the influence of serotonin on brain structure and hippocampal volumes in relation to cognitive functions in AD, as well as its link with biomarkers like CNTF, FGF-4, BMP-6, and MMP-1. Data from 133 ADNI participants with AD included cognitive assessments (CDR-SB), serotonin measurements (Biocrates AbsoluteIDQ p180 kit, UPLC-MS/MS), and neurotrophic factors quantified via multiplex proteomics. Gray matter volume changes were analyzed using Voxel-Based Morphometry (VBM) with MRI. Statistical analyses employed Pearson correlation, bootstrap methods, and FDR-adjusted p-values (< 0.05 or < 0.01) via the Benjamini-Hochberg procedure, alongside nonparametric methods. The analysis found a positive correlation between serotonin levels and total brain (r = 0.229, p = 0.023) and hippocampal volumes (right: r = 0.186, p = 0.032; left: r = 0.210, p = 0.023), even after FDR adjustment. Higher serotonin levels were linked to better cognitive function (negative correlation with CDR-SB, r = -0.230, p = 0.024). Notably, serotonin levels were positively correlated with BMP-6 (r = 0.173, p = 0.047), CNTF (r = 0.216, p = 0.013), FGF-4 (r = 0.176, p = 0.043), and MMP-1 (r = 0.202, p = 0.019), suggesting a link between serotonin and neurogenesis and neuroplasticity. However, after adjusting for multiple comparisons and controlling for confounding factors such as age, gender, education, and APOE genotypes (APOE3 and APOE4), none of the correlations of biomarkers remained statistically significant. In conclusion, increased serotonin levels are associated with improved cognitive function and increased brain volume. However, associations with CNTF, FGF-4, BMP-6, and MMP-1 were not statistically significant after adjustments, highlighting the complexity of serotonin's role in AD and the need for further research.
Rapid adaptation to novel environments is crucial for survival, and this ability is impaired in many neuropsychiatric disorders. Understanding neural adaptation to novelty exposure therefore has therapeutic implications....Rapid adaptation to novel environments is crucial for survival, and this ability is impaired in many neuropsychiatric disorders. Understanding neural adaptation to novelty exposure therefore has therapeutic implications. Here, I found that novelty induces time-dependent theta (4-12Hz) oscillatory dynamics in brain circuits including the medial prefrontal cortex (mPFC), ventral hippocampus (vHPC), and ventral tegmental area (VTA), but not dorsal hippocampus (dHPC), as mice adapt to a novel environment. Local field potential (LFP) recordings were performed while mice were freely behaving in a novel or a familiar arena for 10 min. Initially, mice exhibited increased exploratory behavior upon exposure to novelty, which gradually decreased to levels observed in mice exposed to the familiar arena. Over the same time course, the mPFC, vHPC, and VTA displayed progressively increasing theta power through novelty exposure. Additionally, theta coherence and theta phase synchrony measures demonstrated that novelty weakened the connectivity between these areas, which then gradually strengthened to the level observed in the familiar group. Conversely, mice exposed to the familiar arena showed steady and consistent behavior as well as theta dynamics in all areas. Treatment with a dopamine D1-receptor (D1R) antagonist in the vHPC disrupted neurophysiological adaptation to novelty specifically in the vHPC-mPFC and vHPC-VTA circuits, without affecting behavior. Thus, novelty induces distinct theta dynamics that are not readily dictated by behavior in the mPFC, vHPC, and VTA circuits, a process mediated by D1Rs in the vHPC. The observed time-dependent circuit dynamics in the key learning and memory circuit would provide new insights for treating neuropsychiatric disorders that often show impaired novelty processing.
Coordinated activity of neuronal ensembles is a basis for information processing in the brain. Recent development of miniscope imaging technology enabled recordings of neuronal circuits activity in vivo in freely behavin...Coordinated activity of neuronal ensembles is a basis for information processing in the brain. Recent development of miniscope imaging technology enabled recordings of neuronal circuits activity in vivo in freely behaving animals. Acute stress is believed to affect various hippocampal functions, especially memory. In the current study, we utilized miniscope imaging to investigate the hippocampal neuronal circuits properties in a mouse as function of time and immediately in response to an acute stress, induced by passive restraint, 3 h and 10 days after. Comprehensive quantitative analysis of network activity changes at the neuronal ensembles level revealed highly stable neuronal activity parameters, which exhibited a rapid and robust shift in response to acute stress stimulation. This shift was accompanied by the restructuring of the pairwise-correlated neuronal pairs. Remarkably, we discovered that ensembles activity characteristics returned to the initial state following recovery period, demonstrating hippocampal homeostatic stability at the neuronal circuits level. Obtained results provide an evidence about hippocampal neuronal ensembles activity in response to acute stress over time.
The vast majority of gene mutations and/or gene knockouts result in either no observable changes, or significant deficits in molecular, cellular, or organismal function. However, in a small number of cases, mutant animal...The vast majority of gene mutations and/or gene knockouts result in either no observable changes, or significant deficits in molecular, cellular, or organismal function. However, in a small number of cases, mutant animal models display enhancements in specific behaviors such as learning and memory. To date, most gene deletions shown to enhance cognitive ability generally affect a limited number of pathways such as NMDA receptor- and translation-dependent plasticity, or GABA receptor- and potassium channel-mediated inhibition. While endolysosomal trafficking of AMPA receptors is a critical mediator of synaptic plasticity, mutations in genes that affect AMPAR trafficking either have no effect or are deleterious for synaptic plasticity, learning and memory. NSG2 is one of the three-member family of Neuron-specific genes (NSG1-3), which have been shown to regulate endolysosomal trafficking of a number of proteins critical for neuronal function, including AMPAR subunits (GluA1-2). Based on these findings and the largely universal expression throughout mammalian brain, we predicted that genetic knockout of NSG2 would result in significant impairments across multiple behavioral modalities including motor, affective, and learning/memory paradigms. However, in the current study we show that loss of NSG2 had highly selective effects on associative learning and memory, leaving motor and affective behaviors intact. For instance, NSG2 KO animals performed equivalent to wild-type C57Bl/6n mice on rotarod and Catwalk motor tasks, and did not display alterations in anxiety-like behavior on open field and elevated zero maze tasks. However, NSG2 KO animals demonstrated enhanced recall in the Morris water maze, accelerated reversal learning in a touch-screen task, and accelerated acquisition and enhanced recall on a Trace Fear Conditioning task. Together, these data point to a specific involvement of NSG2 on multiple types of associative learning, and expand the repertoire of pathways that can be targeted for cognitive enhancement.
Trace and delay auditory fear conditioning involve different memory association strategies based on working memory involvement; however, their differences in long-term processing through sleep and extinction training rem...Trace and delay auditory fear conditioning involve different memory association strategies based on working memory involvement; however, their differences in long-term processing through sleep and extinction training remain unclear. While females often exhibit more persistent fear, complicating psychiatric treatment, most studies have primarily focused on how sleep affects initial recall in male mice. We investigated the three-way interaction between tests (trace vs. delay), sleep states, and sex during initial recall, extinction, and post-extinction remote recall. A six-hour post-conditioning sleep deprivation (SD) did not affect freezing behavior during the following day's extinction training of delay fear memory. However, during post-extinction remote recall of delay fear memory, SD prevented spontaneous recovery in males and reduced persistent freezing in females. In contrast, SD rapidly facilitated extinction of trace fear memory. In summary, SD enhances extinction both in the short-term and long-term, depending on the conditioning protocol. These findings highlight the importance of long-term assessments to explore interactions among emotional memory, sleep, and sex differences, with implications for individualized mechanisms underlying post-traumatic stress disorder (PTSD) and its treatments.