The amygdala, social behavior, and danger detection

Oral Oxytocin Blurs Sex Differences in Amygdala Responses to Emotional Scenes

BACKGROUND

Sex differences are shaped both by innate biological differences and the social environment and are frequently observed in human emotional neural responses. Oral administration of oxytocin (OXT), as an alternative and noninvasive intake method, has been shown to produce sex-dependent effects on emotional face processing. However, it is unclear whether oral OXT produces similar sex-dependent effects on processing continuous emotional scenes.

METHODS

The current randomized, double-blind, placebo-controlled neuropsychopharmacological functional magnetic resonance imaging experiment was conducted in 147 healthy participants (OXT = 74, men/women = 37/37; placebo = 73, men/women = 36/37) to examine the oral OXT effect on plasma OXT concentrations and neural response to emotional scenes in both sexes.

RESULTS

At the neuroendocrine level, women showed lower endogenous OXT concentrations than men, but oral OXT increased OXT concentrations equally in both sexes. Regarding neural activity, emotional scenes evoked opposite valence-independent effects on right amygdala activation (women > men) and its functional connectivity with the insula (men > women) in men and women in the placebo group. This sex difference was either attenuated (amygdala response) or even completely eliminated (amygdala-insula functional connectivity) in the OXT group. Multivariate pattern analysis confirmed these findings by developing an accurate sex-predictive neural pattern that included the amygdala and the insula under the placebo but not the OXT condition.

CONCLUSIONS

The results of the current study suggest a pronounced sex difference in neural responses to emotional scenes that was eliminated by oral OXT, with OXT having opposite modulatory effects in men and women. This may reflect oral OXT enhancing emotional regulation to continuous emotional stimuli in both sexes by facilitating appropriate changes in sex-specific amygdala-insula circuitry.

Expanded gray matter atrophy with severity stages of adult comorbid insomnia and sleep apnea

OBJECTIVE

To investigate gray matter volume (GMV) changes in patients with comorbid insomnia and sleep apnea (COMISA) of differing severity and relationships between GMV alterations and clinical measures.

METHODS

Thirty-four COMISA patients and 24 healthy controls (HC) were recruited. All patients underwent structural MRI and completed measures related to respiration, sleep, mood, and cognition. COMISA patients were further divided into a mild and moderate COMISA (MC) and a severe COMISA (SC) group. Changes in GMV of COMISA patients were investigated via VBM. The voxel-wise differences in GMV were compared between HC group and COMISA group. Analysis of covariance (ANCOVA) was performed on individual GMV maps in MC, SC, and HC groups to further investigate effects of different stages of COMISA severity on GMV. Partial correlation analysis was then performed to analyze relationships between altered GMV and clinical measures.

RESULTS

GMV atrophy was mainly located in the temporal lobes and fusiform gyrus in COMISA group. The post-hoc analysis of the ANCOVA revealed temporal lobes and fusiform gyrus atrophy in MC and SC groups compared to HC and the temporal lobe atrophy was expanded in SC group based on cluster size. Moreover, the SC group showed GMV atrophy of the right amygdala compared to both MC and HC groups. Partial correlation analysis revealed positive relationships between the GMV and mood-and cognitive-related measures and negative correlation between GMV and respiration measure.

CONCLUSIONS

Our findings showed GMV atrophy expansion from temporal lobe to limbic system (right amygdala) as severity stages increase in COMISA patients. These findings contribute to our understanding of neurobiological mechanisms underlying different stages of severity in COMISA patients.

Neurophysiological analysis of disadvantageous social inequity: Exploring emotional behavior changes and c-Fos expression in a male rat model

Humans and other animals exhibit aversive behavioral and emotional responses to unequal reward distributions compared with their conspecifics. Despite the significance of this phenomenon, experimental animal models designed to investigate social inequity aversion and delve into the underlying neurophysiological mechanisms are limited. In this study, we developed a rat model to determine the effects of socially equal or unequal reward and stress on emotional changes in male rats. During the training session, the rats were trained to escape when a sound cue was presented, and they were assigned to one of the following groups: all escaping rats [advantageous equity (AE)], freely moving rats alongside a restrained rat [advantageous inequity (AI)], all restrained rats [disadvantageous equity (DE)], and a rat restrained in the presence of freely moving companions [disadvantageous inequity (DI)]. During the test session, rats in the advantageous group (AE and AI) escaped after the cue sound (expected reward acquisition), whereas rats in the disadvantageous group (DE and DI) could not escape despite the cue being presented (expected reward deprivation). Emotional alteration induced by exposure to restraint stress under various social interaction circumstances was examined using an open field test. Notably, the DI group displayed reduced exploration of the center zone during the open field tests compared with the other groups, indicating heightened anxiety-like behaviors in response to reward inequity. Immunohistochemical analysis revealed increased c-Fos expression in the medial prefrontal and orbitofrontal cortices, coupled with reduced c-Fos expression in the striatum and nucleus accumbens under DI conditions, in contrast to the other experimental conditions. These findings provide compelling evidence that rats are particularly sensitive to reward inequity, shedding light on the neurophysiological basis for distinct cognitive processes that manifest when individuals are exposed to social equity and inequity situations.

Infant pain vs. pain with parental suppression: Immediate and enduring impact on brain, pain and affect

BACKGROUND

In the short term, parental presence while a human infant is in pain buffers the immediate pain responses, although emerging evidence suggests repeated social buffering of pain may have untoward long-term effects.

METHODS/FINDING

To explore the short- and long-term impacts of social buffering of pain, we first measured the infant rat pup's [postnatal day (PN) 8, or 12] response to mild tail shock with the mother present compared to shock alone or no shock. Shock with the mother reduced pain-related behavioral activation and USVs of pups at both ages and reduced Fos expression in the periaqueductal gray, hypothalamic paraventricular nucleus, and the amygdala at PN12 only. At PN12, shock with the mother compared to shock alone differentially regulated expression of several hundred genes related to G-protein-coupled receptors (GPCRs) and neural development, whereas PN8 pups showed a less robust and less coherent expression pattern. In a second set of experiments, pups were exposed to daily repeated Shock-mother pairings (or controls) at PN5-9 or PN10-14 (during and after pain sensitive period, respectively) and long-term outcome assessed in adults. Shock+mother pairing at PN5-9 reduced adult carrageenan-induced thermal hyperalgesia and reduced Fos expression, but PN10-14 pairings had minimal impact. The effect of infant treatment on adult affective behavior showed a complex treatment by age dependent effect. Adult social behavior was decreased following Shock+mother pairings at both PN5-9 and PN10-14, whereas shock alone had no effect. Adult fear responses to a predator odor were decreased only by PN10-14 treatment and the infant Shock alone and Shock+mother did not differ.

CONCLUSIONS/SIGNIFICANCE

Overall, integrating these results into our understanding of long-term programming by repeated infant pain experiences, the data suggest that pain experienced within a social context impacts infant neurobehavioral responses and initiates an altered developmental trajectory of pain and affect processing that diverges from experiencing pain alone.

Are vipers prototypic fear-evoking snakes? A cross-cultural comparison of Somalis and Czechs

Snakes are known as highly fear-evoking animals, eliciting preferential attention and fast detection in humans. We examined the human fear response to snakes in the context of both current and evolutionary experiences, conducting our research in the cradle of humankind, the Horn of Africa. This region is characterized by the frequent occurrence of various snake species, including deadly venomous viperids (adders) and elapids (cobras and mambas). We conducted experiments in Somaliland and compared the results with data from Czech respondents to address the still unresolved questions: To which extent is human fear of snakes affected by evolutionary or current experience and local culture? Can people of both nationalities recognize venomous snakes as a category, or are they only afraid of certain species that are most dangerous in a given area? Are respondents of both nationalities equally afraid of deadly snakes from both families (Viperidae, Elapidae)? We employed a well-established picture-sorting approach, consisting of 48 snake species belonging to four distinct groups. Our results revealed significant agreement among Somali as well as Czech respondents. We found a highly significant effect of the stimulus on perceived fear in both populations. Vipers appeared to be the most salient stimuli in both populations, as they occupied the highest positions according to the reported level of subjectively perceived fear. The position of vipers strongly contrasts with the fear ranking of deadly venomous elapids, which were in lower positions. Fear scores of vipers were significantly higher in both populations, and their best predictor was the body width of the snake. The evolutionary, cultural, and cognitive aspects of this phenomenon are discussed.

Rodent models of early adversity: Impacts on developing social behavior circuitry and clinical implications

Flexible and context-appropriate social functioning is key for survival across species. This flexibility also renders social behavior highly plastic, particularly during early development when attachment to caregiver can provide a template for future social processing. As a result, early caregiving adversity can have unique and lasting impacts on social behavior and even confer vulnerability to psychiatric disorders. However, the neural circuit mechanisms translating experience to outcome remain poorly understood. Here, we consider social behavior scaffolding through the lens of reward and threat processing. We begin by surveying several complementary rodent models of early adversity, which together have highlighted impacts on neural circuits processing social cues. We next explore these circuits underlying perturbed social functioning with focus on dopamine (DA) and its role in regions implicated in social and threat processing such as the prefrontal cortex (PFC), basolateral amygdala (BLA) and the lateral habenula (LHb). Finally, we turn to human populations once more to examine how altered DA signaling and LHb dysfunction may play a role in social anhedonia, a common feature in diagnoses such as schizophrenia and major depressive disorder (MDD). We argue that this translational focus is critical for identifying specific features of adversity that confer heightened vulnerability for clinical outcomes involving social cue processing.

Neural activity patterns differ between learning contexts in a social fish

Learning and decision-making are greatly influenced by context. When navigating a complex social world, individuals must quickly ascertain where to gain important resources and which group members are useful sources of such information. Such dynamic behavioural processes require neural mechanisms that are flexible across contexts. Here we examine how the social context influences the learning response during a cue discrimination task and the neural activity patterns that underlie acquisition of this novel information. Using the cichlid fish, Astatotilapia burtoni, we show that learning of the task is faster in social groups than in a non-social context. We quantify the neural activity patterns by examining the expression of Fos, an immediate-early gene, across brain regions known to play a role in social behaviour and learning (such as the putative teleost homologues of the mammalian hippocampus, basolateral amygdala and medial amygdala/BNST complex). We find that neural activity patterns differ between social and non-social contexts. Taken together, our results suggest that while the same brain regions may be involved in the learning of a cue association, the activity in each region reflects an individual's social context.

Neuroanatomical changes associated with conduct disorder in boys: influence of childhood maltreatment

Childhood maltreatment (CM) poses a serious risk to the physical, emotional and psychological well-being of children, and can advance the development of maladaptive behaviors, including conduct disorder (CD). CD involves repetitive, persistent violations of others' basic rights and societal norms. Little is known about whether and how CM influences the neural mechanisms underlying CD, and CD-characteristic neuroanatomical changes have not yet been defined in a structural magnetic resonance imaging (sMRI) study. Here, we used voxel-based morphometry (VBM) and surface-based morphometry (SBM) to investigate the influence of the CD diagnosis and CM on the brain in 96 boys diagnosed with CD (62 with CM) and 86 typically developing (TD) boys (46 with CM). The participants were 12-17 years of age. Compared to the CM- CD group, the CM+ CD group had structural gray matter (GM) alterations in the fronto-limbic regions, including the left amygdala, right posterior cingulate cortex (PCC), right putamen, right dorsolateral prefrontal cortex (dlPFC) and right anterior cingulate cortex (ACC). We also found boys with CD exhibited increased GM volume in bilateral dorsomedial prefrontal cortex (dmPFC), as well as decreased GM volume and decreased gyrification in the left superior temporal gyrus (STG) relative to TD boys. Regional GM volume correlated with aggression and conduct problem severity in the CD group, suggesting that the GM changes may contribute to increased aggression and conduct problems in boys with CD who have suffered CM. In conclusion, these results demonstrate previously unreported CM-associated distinct brain structural changes among CD-diagnosed boys.

Fast Unconscious Processing of Emotional Stimuli in Early Stages of the Visual Cortex

Several cortical and subcortical brain areas have been reported to be sensitive to the emotional content of subliminal stimuli. However, the timing of these activations remains unclear. Our scope was to detect the earliest cortical traces of emotional unconscious processing of visual stimuli by recording event-related potentials (ERPs) from 43 participants. Subliminal spiders (emotional) and wheels (neutral), sharing similar low-level visual parameters, were presented at two different locations (fixation and periphery). The differential (peak-to-peak) amplitude from CP1 (77 ms from stimulus onset) to C2 (100 ms), two early visual ERP components originated in V1/V2 according to source localization analyses, was analyzed via Bayesian and traditional frequentist analyses. Spiders elicited greater CP1–C2 amplitudes than wheels when presented at fixation. This fast effect of subliminal stimulation—not reported previously to the best of our knowledge—has implications in several debates: 1) The amygdala cannot be mediating these effects, 2) latency of other evaluative structures recently proposed, such as the visual thalamus, is compatible with these results, 3) the absence of peripheral stimuli effects points to a relevant role of the parvocellular visual system in unconscious processing.

Three-Dimensional Atlas of the Human Amygdala Subnuclei Constructed Using Immunohistochemical and Ultrahigh-Field Magnetic Resonance Imaging Data

The amygdala is central for social and emotional processing and has been implicated in various disorders including autism spectrum disorder (ASD) and Alzheimer's disease (AD). Animal research and some limited research with humans has indicated that widespread alterations in neuronal development or neuronal loss in the basolateral and other amygdala subnuclei may be a contributing factor to variations in social behaviours. Yet, the basolateral amygdala is comprised of three subnuclei, each with a specialized role related to the coordination of emotional regulation. Due to their small size, the nuclei which comprise the basolateral amygdala remain understudied in humans in vivo. In this work, we describe methodology to examine the basolateral amygdala and other subnuclei in human ex vivo medial temporal lobe prosections using ultrahigh-field magnetic resonance imaging (MRI) at 9.4 T. Manual segmentations of the amygdala subnuclei on MR images, verified with immunohistochemical data, provide a robust three-dimensional atlas of the human amygdala. The goal is to apply the atlas to in vivo MRI scans to examine basolateral amygdala macrostructural development attributed to social cognitive dysfunction in ASD and other neurodevelopmental disorders. Furthermore, the atlas can be used to examine MRI-based correlates of neuronal loss commonly seen in neurodegenerative disorders.

A role of anterior cingulate cortex in the emergence of worker-parasite relationship

We studied the brain mechanisms underlying action selection in a social dilemma setting in which individuals' effortful gains are unfairly distributed among group members. A stable "worker-parasite" relationship developed when three individually operant-conditioned rats were placed together in a Skinner box equipped with response lever and food dispenser on opposite sides. Specifically, one rat, the "worker," engaged in lever-pressing while the other two "parasitic" rats profited from the worker's effort by crowding the feeder in anticipation of food. Anatomically, c-Fos expression in the anterior cingulate cortex (ACC) was significantly higher in worker rats than in parasite rats. Functionally, ACC inactivation suppressed the worker's lever-press behavior drastically under social, but only mildly under individual, settings. Transcriptionally, GABA_A receptor- and potassium channel-related messenger RNA expressions were reliably lower in the worker's, relative to parasite's, ACC. These findings indicate the requirement of ACC activation for the expression of exploitable, effortful behavior, which could be mediated by molecular pathways involving GABA_A receptor/potassium channel proteins.

Widespread Pressure Delivered by a Weighted Blanket Reduces Chronic Pain: A Randomized Controlled Trial

Pleasant sensation is an underexplored avenue for modulation of chronic pain. Deeper pressure is perceived as pleasant and calming, and can improve sleep. Although pressure can reduce acute pain, its effect on chronic pain is poorly characterized. The current remote, double-blind, randomized controlled trial tested the hypothesis that wearing a heavy weighted blanket - providing widespread pressure to the body - relative to a light weighted blanket would reduce ratings of chronic pain, mediated by improvements in anxiety and sleep. Ninety-four adults with chronic pain were randomized to wear a 15-lb. (heavy) or 5-lb. (light) weighted blanket during a brief trial and overnight for one week. Measures of anxiety and chronic pain were collected pre- and post-intervention, and ratings of pain intensity, anxiety, and sleep were collected daily. After controlling for expectations and trait anxiety, the heavy weighted blanket produced significantly greater reductions in broad perceptions of chronic pain than the light weighted blanket (Cohen's f = .19, CI [-1.97, -.91]). This effect was stronger in individuals with high trait anxiety (P = .02). However, weighted blankets did not alter pain intensity ratings. Pain reductions were not mediated by anxiety or sleep. Given that the heavy weighted blanket was associated with greater modulation of affective versus sensory aspects of chronic pain, we propose that the observed reductions are due to interoceptive and social/affective effects of deeper pressure. Overall, we demonstrate that widespread pressure from a weighted blanket can reduce the severity of chronic pain, offering an accessible, home-based tool for chronic pain. The study purpose, targeted condition, study design, and primary and secondary outcomes were pre-registered in ClinicalTrials.gov (NCT04447885: "Weighted Blankets and Chronic Pain"). Perspective: This randomized-controlled trial showed that a 15-lb weighted blanket produced significantly greater reductions in broad perceptions of chronic pain relative to a 5-lb weighted blanket, particularly in highly anxious individuals. These findings are relevant to patients and providers seeking home-based, nondrug therapies for chronic pain relief.

Biological implications of genetic variations in autism spectrum disorders from genomics studies

Autism spectrum disorder (ASD) is a highly heterogeneous neurodevelopmental condition characterized by atypical social interaction and communication together with repetitive behaviors and restricted interests. The prevalence of ASD has been increased these years. Compelling evidence has shown that genetic factors contribute largely to the development of ASD. However, knowledge about its genetic etiology and pathogenesis is limited. Broad applications of genomics studies have revealed the importance of gene mutations at protein-coding regions as well as the interrupted non-coding regions in the development of ASD. In this review, we summarize the current evidence for the known molecular genetic basis and possible pathological mechanisms as well as the risk genes and loci of ASD. Functional studies for the underlying mechanisms are also implicated. The understanding of the genetics and genomics of ASD is important for the genetic diagnosis and intervention for this condition.

CA, Klingner CM. The Right Hemisphere Is Responsible for the Greatest Differences in Human Brain Response to High-Arousing Emotional versus Neutral Stimuli: A MEG Study

Studies investigating human brain response to emotional stimuli-particularly high-arousing versus neutral stimuli-have obtained inconsistent results. The present study was the first to combine magnetoencephalography (MEG) with the bootstrapping method to examine the whole brain and identify the cortical regions involved in this differential response. Seventeen healthy participants (11 females, aged 19 to 33 years; mean age, 26.9 years) were presented with high-arousing emotional (pleasant and unpleasant) and neutral pictures, and their brain responses were measured using MEG. When random resampling bootstrapping was performed for each participant, the greatest differences between high-arousing emotional and neutral stimuli during M300 (270-320 ms) were found to occur in the right temporo-parietal region. This finding was observed in response to both pleasant and unpleasant stimuli. The results, which may be more robust than previous studies because of bootstrapping and examination of the whole brain, reinforce the essential role of the right hemisphere in emotion processing.

Astrogliosis in juvenile non-human primates 2 years after infant anaesthesia exposure

BACKGROUND

Infant anaesthesia causes acute brain cell apoptosis, and later in life cognitive deficits and behavioural alterations, in non-human primates (NHPs). Various brain injuries and neurodegenerative conditions are characterised by chronic astrocyte activation (astrogliosis). Glial fibrillary acidic protein (GFAP), an astrocyte-specific protein, increases during astrogliosis and remains elevated after an injury. Whether infant anaesthesia is associated with a sustained increase in GFAP is unknown. We hypothesised that GFAP is increased in specific brain areas of NHPs 2 yr after infant anaesthesia, consistent with prior injury.

METHODS

Eight 6-day-old NHPs per group were exposed to 5 h isoflurane once (1×) or three times (3×), or to room air as a control (Ctr). Two years after exposure, their brains were assessed for GFAP density changes in the primary visual cortex (V1), perirhinal cortex (PRC), hippocampal subiculum, amygdala, and orbitofrontal cortex (OFC). We also assessed concomitant microglia activation and hippocampal neurogenesis.

RESULTS

Compared with controls, GFAP densities in V1 were increased in exposed groups (Ctr: 0.208 [0.085-0.427], 1×: 0.313 [0.108-0.533], 3×: 0.389 [0.262-0.652]), whereas the density of activated microglia was unchanged. In addition, GFAP densities were increased in the 3× group in the PRC and the subiculum, and in both exposure groups in the amygdala, but there was no increase in the OFC. There were no differences in hippocampal neurogenesis among groups.

CONCLUSIONS

Two years after infant anaesthesia, NHPs show increased GFAP without concomitant microglia activation in specific brain areas. These long-lasting structural changes in the brain caused by infant anaesthesia exposure may be associated with functional alterations at this age.

The Missing Link in Early Emotional Processing

Initial evaluation structures (IESs) currently proposed as the earliest detectors of affective stimuli (e.g., amygdala, orbitofrontal cortex, or insula) are high-order structures (a) whose response latency cannot account for the first visual cortex emotion-related response (~80 ms), and (b) lack the necessary infrastructure to locally analyze the visual features that define emotional stimuli. Several thalamic structures accomplish both criteria. The lateral geniculate nucleus (LGN), a first-order thalamic nucleus that actively processes visual information, with the complement of the thalamic reticular nucleus (TRN) are proposed as core IESs. This LGN–TRN tandem could be supported by the pulvinar, a second-order thalamic structure, and by other extrathalamic nuclei. The visual thalamus, scarcely explored in affective neurosciences, seems crucial in early emotional evaluation.

Toward a neuropsychology of political orientation: exploring ideology in patients with frontal and midbrain lesions

How do people form their political beliefs? In an effort to address this question, we adopt a neuropsychological approach. In a natural experiment, we explored links between neuroanatomy and ideological preferences in two samples of brain lesion patients in New York City. Specifically, we compared the political orientations of patients with frontal lobe lesions, patients with amygdala lesions and healthy control subjects. Lesion type classification analyses revealed that people with frontal lesions held more conservative (or less liberal) beliefs than those with anterior temporal lobe lesions or no lesions. Additional analyses predicting ideology by extent of damage provided convergent evidence that greater damage in the dorsolateral prefrontal cortex-but not the amygdala-was associated with greater conservatism. These findings were robust to model specifications that adjusted for demographic, mood, and affect-related variables. Although measures of executive function failed to mediate the relationship between frontal lesions and ideology, our findings suggest that the prefrontal cortex may play a role in promoting the development of liberal ideology. Our approach suggests useful directions for future work to address the issue of whether biological developments precede political attitudes or vice versa-or both. This article is part of the theme issue 'The political brain: neurocognitive and computational mechanisms'.

Bilateral amygdala damage linked to impaired ability to predict others' fear but preserved moral judgements about causing others fear

The amygdala is a subcortical structure implicated in both the expression of conditioned fear and social fear recognition. Social fear recognition deficits following amygdala lesions are often interpreted as reflecting perceptual deficits, or the amygdala's role in coordinating responses to threats. But these explanations fail to capture why amygdala lesions impair both physiological and behavioural responses to multimodal fear cues and the ability to identify them. We hypothesized that social fear recognition deficits following amygdala damage reflect impaired conceptual understanding of fear. Supporting this prediction, we found specific impairments in the ability to predict others' fear (but not other emotions) from written scenarios following bilateral amygdala lesions. This finding is consistent with the suggestion that social fear recognition, much like social recognition of states like pain, relies on shared internal representations. Preserved judgements about the permissibility of causing others fear confirms suggestions that social emotion recognition and morality are dissociable.

Targeting Uric Acid Prevents Brain Injury and Anxiety in a Rat Model of Hemorrhagic Shock

ABSTRACT

Secondary brain injury following hemorrhagic shock (HS) is a frequent complication in patients, even in the absence of direct brain trauma, leading to behavioral changes and more specifically anxiety and depression. Despite preclinical studies showing inflammation and apoptosis in the brain after HS, none have addressed the impact of circulating mediators. Our group demonstrated an increased uric acid (UA) circulation in rats following HS. Since UA is implicated in endothelial dysfunction and inflammatory response, we hypothesized UA could alter the blood-brain barrier (BBB) and impact the brain. Male Wistar rats were randomly assigned to: SHAM, HS (hemorrhagic shock) and HS + U (hemorrhagic shock + 1.5 mg/kg of uricase). The uricase intervention, specifically targeting UA, was administered during fluid resuscitation. It prevented BBB dysfunction (fluorescein sodium salt permeability and expression of intercellular adhesion molecule-1) following HS. As for neuroinflammation, all of the results obtained (MPO activity; Iba1 and GFAP expression) showed a significant increase after HS, also prevented by the uricase. The same pattern was observed after quantification of apoptosis (caspase-3 activity and TUNEL) and neurodegeneration (Fluoro-Jade). Finally, the forced swim, elevated plus maze, and social interaction tests detected anxiety-like behavior after HS, which was blunted in rats treated with the uricase. In conclusion, we have identified UA as a new circulatory inflammatory mediator, responsible for brain alterations and anxious behavior after HS in a murine model. The ability to target UA holds the potential of an adjunctive therapeutic solution to reduce brain dysfunction related to hemorrhagic shock in human.

Effects of Emotional Music on Facial Emotion Recognition in Children with Autism Spectrum Disorder (ASD)

Impaired facial emotion recognition in children with Autism Spectrum Disorder (ASD) is in contrast to their intact emotional music recognition. This study tested whether emotion congruent music enhances facial emotion recognition. Accuracy and reaction times were assessed for 19 children with ASD and 31 controls in a recognition task with angry, happy, or sad faces. Stimuli were shown with either emotionally congruent or incongruent music or no music. Although children with ASD had higher reaction times than controls, accuracy only differed when incongruent or no music was played, indicating that congruent emotional music can boost facial emotion recognition in children with ASD. Emotion congruent music may support emotion recognition in children with ASD, and thus may improve their social skills.

Temporal dynamics of amygdala response to emotion- and action-relevance

It has been proposed that the human amygdala may not only encode the emotional value of sensory events, but more generally mediate the appraisal of their relevance for the individual's goals, including relevance for action or task-based needs. However, emotional and non-emotional/action-relevance might drive amygdala activity through distinct neural signals, and the relative timing of both kinds of responses remains undetermined. Here, we recorded intracranial event-related potentials from nine amygdalae of patients undergoing epilepsy surgery, while they performed variants of a Go/NoGo task with faces and abstract shapes, where emotion- and action-relevance were orthogonally manipulated. Our results revealed early amygdala responses to emotion facial expressions starting ~ 130 ms after stimulus-onset. Importantly, the amygdala responded to action-relevance not only with face stimuli but also with abstract shapes (squares), and these relevance effects consistently occurred in later time-windows (starting ~ 220 ms) for both faces and squares. A similar dissociation was observed in gamma activity. Furthermore, whereas emotional responses habituated over time, the action-relevance effect increased during the course of the experiment, suggesting progressive learning based on the task needs. Our results support the hypothesis that the human amygdala mediates a broader relevance appraisal function, with the processing of emotion-relevance preceding temporally that of action-relevance.

Aversive perception in a threat context: Separate and independent neural activation

Unpleasant, compared to neutral, scenes reliably prompt enhanced functional brain activity in the amygdala and inferotemporal cortex. Considering data from psychophysiological studies in which defensive reactivity is further enhanced when viewing unpleasant scenes under threat of shock (compared to safety), the current study investigates functional activation in the amygdala-inferotemporal circuit when unpleasant (or neutral) scenes are viewed under threat of shock or safety. In this paradigm, a cue signaling threat or safety was presented in conjunction with either an unpleasant or neutral picture. Replicating previous studies, unpleasant, compared to neutral, scenes reliably enhanced activation in the amygdala and inferotemporal cortex. Functional activity in these regions, however, did not differ whether scenes were presented in a context threatening shock exposure, compared to safety, which instead activated regions of the anterior insula and cingulate cortex. Taken together, the data support a view in which neural regions activated in different defensive situations act independently.

Adverse caregiving in infancy blunts neural processing of the mother

The roots of psychopathology frequently take shape during infancy in the context of parent-infant interactions and adversity. Yet, neurobiological mechanisms linking these processes during infancy remain elusive. Here, using responses to attachment figures among infants who experienced adversity as a benchmark, we assessed rat pup cortical local field potentials (LFPs) and behaviors exposed to adversity in response to maternal rough and nurturing handling by examining its impact on pup separation-reunion with the mother. We show that during adversity, pup cortical LFP dynamic range decreased during nurturing maternal behaviors, but was minimally impacted by rough handling. During reunion, adversity-experiencing pups showed aberrant interactions with mother and blunted cortical LFP. Blocking pup stress hormone during either adversity or reunion restored typical behavior, LFP power, and cross-frequency coupling. This translational approach suggests adversity-rearing produces a stress-induced aberrant neurobehavioral processing of the mother, which can be used as an early biomarker of later-life pathology.

Amygdala activity related to perceived social support

Perceived social support enhances well-being and prevents stress-related ill-being. A recent structural neuroimaging study reported that the amygdala volume is positively associated with perceived social support. However, it remains unknown how neural activity in this region and functional connectivity (FC) between this and other regions are related to perceived social support. To investigate these issues, resting-state functional magnetic resonance imaging was performed to analyze the fractional amplitude of low-frequency fluctuation (fALFF). Perceived social support was evaluated using the Multidimensional Scale of Perceived Social Support (MSPSS). Lower fALFF values in the bilateral amygdalae were associated with higher MSPSS scores. Additionally, stronger FC between the left amygdala and right orbitofrontal cortex and between the left amygdala and bilateral precuneus were associated with higher MSPSS scores. The present findings suggest that reduced amygdala activity and heightened connectivity between the amygdala and other regions underlie perceived social support and its positive functions.

During infant maltreatment, stress targets hippocampus, but stress with mother present targets amygdala and social behavior

Infant maltreatment increases vulnerability to physical and mental disorders, yet specific mechanisms embedded within this complex infant experience that induce this vulnerability remain elusive. To define critical features of maltreatment-induced vulnerability, rat pups were reared from postnatal day 8 (PN8) with a maltreating mother, which produced amygdala and hippocampal deficits and decreased social behavior at PN13. Next, we deconstructed the maltreatment experience to reveal sufficient and necessary conditions to induce this phenotype. Social behavior and amygdala deficits (volume, neurogenesis, c-Fos, local field potential) required combined chronic high corticosterone and maternal presence (not maternal behavior). Hippocampal deficits were induced by chronic high corticosterone regardless of social context. Causation was shown by blocking corticosterone during maltreatment and suppressing amygdala activity during social behavior testing. These results highlight (1) that early life maltreatment initiates multiple pathways to pathology, each with distinct causal mechanisms and outcomes, and (2) the importance of social presence on brain development.

Emotion regulation via visual avoidance: Insights from neurological patients

Visual avoidance of unpleasant stimuli (i.e., strategic positioning of eyes, head and torso away from an environmental stimulus) is a common attentional control behavior that may down-regulate emotion by reducing visual input. Despite its ubiquity, relatively little is known about how visual avoidance is affected by neurological diseases that impact neural circuits involved in emotional functioning. We examined visual avoidance in 56 behavioral variant frontotemporal dementia (bvFTD) patients, 43 Alzheimer's disease (AD) patients, and 34 healthy controls. Participants came to our laboratory and viewed an extremely disgusting film clip while visual avoidance was measured using behavioral coding of head, body, and eye position. Controlling for differences in cognitive functioning, bvFTD patients were less likely to engage in visual avoidance behaviors than both AD patients and healthy controls. Additional analyses revealed that diminished visual avoidance in this task was associated with lower levels of real-world emotion regulation but not with emotion reactivity as reported by the primary caregiver.

Gut microbiome and brain functional connectivity in infants-a preliminary study focusing on the amygdala

Recently, there has been a surge of interest in the possibility that microbial communities inhabiting the human gut could affect cognitive development and increase risk for mental illness via the "microbiome-gut-brain axis." Infancy likely represents a critical period for the establishment of these relationships, as it is the most dynamic stage of postnatal brain development and a key period in the maturation of the microbiome. Indeed, recent reports indicate that characteristics of the infant gut microbiome are associated with both temperament and cognitive performance. The neural circuits underlying these relationships have not yet been delineated. To address this gap, resting-state fMRI scans were acquired from 39 1-year-old human infants who had provided fecal samples for identification and relative quantification of bacterial taxa. Measures of alpha diversity were generated and tested for associations with measures of functional connectivity. Primary analyses focused on the amygdala as manipulation of the gut microbiota in animal models alters the structure and neurochemistry of this brain region. Secondary analyses explored functional connectivity of nine canonical resting-state functional networks. Alpha diversity was significantly associated with functional connectivity between the amygdala and thalamus and between the anterior cingulate cortex and anterior insula. These regions play an important role in processing/responding to threat. Alpha diversity was also associated with functional connectivity between the supplementary motor area (SMA, representing the sensorimotor network) and the inferior parietal lobule (IPL). Importantly, SMA-IPL connectivity also related to cognitive outcomes at 2 years of age, suggesting a potential pathway linking gut microbiome diversity and cognitive outcomes during infancy. These results provide exciting new insights into the gut-brain axis during early human development and should stimulate further studies into whether microbiome-associated changes in brain circuitry influence later risk for psychopathology.

The components of the adolescent brain and its unique sensitivity to sexually explicit material

INTRODUCTION

The focus of this brief literature review is to explore whether there is a relationship between the unique anatomical and physiological paradigms of the adolescent brain and an increased sensitivity to sexually explicit material.

METHODS

The EBSCO Research Data bases were searched using the following key terms: adolescence, adolescent brain development, neuroplasticity, sexually explicit material, sexualization, and pornography.

RESULTS

The literature highlighted several components of the adolescent brain that are different than the mature brain. These include: an immature prefrontal cortex and over-responsive limbic and striatal circuits, heightened period for neuroplasticity, overactive dopamine system, a pronounced HPA axis, augmented levels of testosterone, and the unique impact of steroid hormones. The physiological response to sexually explicit material is delineated. The overlap of key areas associated with the unique adolescent brain development and sexually explicit material is noteworthy. A working model summary that compares the response of the adult and adolescent brain to the same sexually explicit stimulus is outlined.

CONCLUSIONS

The literature suggests that the adolescent brain may indeed be more sensitive to sexually explicit material, but due to a lack of empirical studies this question cannot be answered definitively. Suggestions for future research are given to further advance the work in this applicable field of today.

Social interaction-induced activation of RNA splicing in the amygdala of microbiome-deficient mice

Social behaviour is regulated by activity of host-associated microbiota across multiple species. However, the molecular mechanisms mediating this relationship remain elusive. We therefore determined the dynamic, stimulus-dependent transcriptional regulation of germ-free (GF) and GF mice colonised post weaning (exGF) in the amygdala, a brain region critically involved in regulating social interaction. In GF mice the dynamic response seen in controls was attenuated and replaced by a marked increase in expression of splicing factors and alternative exon usage in GF mice upon stimulation, which was even more pronounced in exGF mice. In conclusion, we demonstrate a molecular basis for how the host microbiome is crucial for a normal behavioural response during social interaction. Our data further suggest that social behaviour is correlated with the gene-expression response in the amygdala, established during neurodevelopment as a result of host-microbe interactions. Our findings may help toward understanding neurodevelopmental events leading to social behaviour dysregulation, such as those found in autism spectrum disorders (ASDs).

In our bodies, there are at least as many microbial cells as human cells. These microbes, known collectively as the microbiome, influence the activity of our brain and also our behaviour. Studies in species from insects to primates have shown that the microbiome affects social behaviour in particular. For example, germ-free mice, which grow up in a sterile environment and thus have no bacteria in or on their bodies, are less sociable than normal mice.

For animals to show behaviours such as social interaction, cells in specific regions of the brain must change the activity of their genes. These brain regions include the amygdala, which is part of the brain’s emotion processing network, and also contributes to fear and anxiety responses. Stilling et al. set out to determine whether gene activity in the amygdala during social interaction differs between germ-free mice and those with a normal microbiome.

Stilling et al. placed each mouse into a box with three chambers. One chamber contained an unfamiliar mouse while another contained an inanimate object. Germ-free mice were less sociable and spent less time than control animals interacting with the unfamiliar mouse. Before entering either test chamber, the germ-free animals showed signs of excessive activity in the amygdala. During social interaction, they displayed a strikingly different pattern of gene activity in this brain region compared to controls. In particular, they had increased levels of a process called alternative splicing. This process enables cells to produce many different proteins from a single gene.

These results reveal one of the steps leading from absence of bacteria during brain development to reduced sociability in adulthood in mice. Increases in gene activity in the amygdala may provide clues to the processes underlying reduced sociability in people with autism spectrum disorders. This new study thus deepens our understanding of the link between the microbiome and brain health.

Transient Hypothyroidism During Lactation Arrests Myelination in the Anterior Commissure of Rats. A Magnetic Resonance Image and Electron Microscope Study

Thyroid hormone deficiency at early postnatal ages affects the cytoarchitecture and function of neocortical and telencephalic limbic areas, leading to impaired associative memory and in a wide spectrum of neurological and mental diseases. Neocortical areas project interhemispheric axons mostly through the corpus callosum and to a lesser extent through the anterior commissure (AC), while limbic areas mostly project through the AC and hippocampal commissures. Functional magnetic resonance data from children with late diagnosed congenital hypothyroidism and abnormal verbal memory processing, suggest altered ipsilateral and contralateral telencephalic connections. Gestational hypothyroidism affects AC development but the possible effect of transient and chronic postnatal hypothyroidism, as occurs in late diagnosed neonates with congenital hypothyroidism and in children growing up in iodine deficient areas, still remains unknown. We studied AC development using in vivo magnetic resonance imaging and electron microscopy in hypothyroid and control male rats. Four groups of methimazole (MMI) treated rats were studied. One group was MMI-treated from postnatal day (P) 0 to P21; some of these rats were also treated with L-thyroxine (T4) from P15 to P21, as a model for early transient hypothyroidism. Other rats were MMI-treated from P0 to P150 and from embryonic day (E) 10 to P170, as a chronic hypothyroidism group. The results were compared with age paired control rats. The normalized T2 signal using magnetic resonance image was higher in MMI-treated rats and correlated with the number and percentage of myelinated axons. Using electron microscopy, we observed decreased myelinated axon number and density in transient and chronic hypothyroid rats at P150, unmyelinated axon number increased slightly in chronic hypothyroid rats. In MMI-treated rats, the myelinated axon g-ratio and conduction velocity was similar to control rats, but with a decrease in conduction delays. These data show that early postnatal transient and chronic hypothyroidism alters AC maturation that may affect the transfer of information through the AC. The alterations cannot be recovered after delayed T4-treatment. Our data support the neurocognitive delay found in late T4-treated children with congenital hypothyroidism.

Speculations on the Evolutionary Origins of System Justification

For centuries, philosophers and social theorists have wondered why people submit voluntarily to tyrannical leaders and oppressive regimes. In this article, we speculate on the evolutionary origins of system justification, that is, the ways in which people are motivated (often nonconsciously) to defend and justify existing social, economic, and political systems. After briefly recounting the logic of system justification theory and some of the most pertinent empirical evidence, we consider parallels between the social behaviors of humans and other animals concerning the acceptance versus rejection of hierarchy and dominance. Next, we summarize research in human neuroscience suggesting that specific brain regions, such as the amygdala and the anterior cingulate cortex, may be linked to individual differences in ideological preferences concerning (in)equality and social stability as well as the successful navigation of complex, hierarchical social systems. Finally, we consider some of the implications of a system justification perspective for the study of evolutionary psychology, political behavior, and social change.

Magnetic Resonance Imaging and Anatomical Correlation of Human Temporal Lobe Landmarks, in 3D Euclidean Space: A Study of Control and Alzheimer's Disease Subjects

BACKGROUND

The medial temporal lobe (MTL), and in particular the hippocampal formation, is essential in the processing and consolidation of declarative memory. The 3D environment of the anatomical structures contained in the MTL is an important issue.

OBJECTIVE

Our aim was to explore the spatial relationship of the anatomical structures of the MTL and changes in aging and/or Alzheimer's disease (AD).

METHODS

MTL anatomical landmarks are identified and registered to create a 3D network. The brain network is quantitatively described as a plane, rostrocaudally-oriented, and presenting Euclidean/real distances. Correspondence between 1.5T RM, 3T RM, and histological sections were assessed to determine the most important recognizable changes in AD, based on statistical significance.

RESULTS

In both 1.5T and 3T RM images and histology, inter-rater reliability was high. Sex and hemisphere had no influence on network pattern. Minor changes were found in relation to aging. Distances from the temporal pole to the dentate gyrus showed the most significant differences when comparing control and AD groups. The best discriminative distance between control and AD cases was found in the temporal pole/dentate gyrus rostrocaudal length in histological sections. Moreover, more distances between landmarks were required to obtain 100% discrimination between control (divided into <65 years or >65 years) and AD cases.

DISCUSSION

Changes in the distance between MTL anatomical landmarks can successfully be detected by using measurements of 3D network patterns in control and AD cases.

Impairment of social behaviors in Arhgef10 knockout mice

Background

Impaired social interaction is one of the essential features of autism spectrum disorder (ASD). Our previous copy number variation (CNV) study discovered a novel deleted region associated with ASD. One of the genes included in the deleted region is ARHGEF10. A missense mutation of ARHGEF10 has been reported to be one of the contributing factors in several diseases of the central nervous system. However, the relationship between the loss of ARHGEF10 and the clinical symptoms of ASD is unclear.

Methods

We generated Arhgef10 knockout mice as a model of ASD and characterized the social behavior and the biochemical changes in the brains of the knockout mice.

Results

Compared with their wild-type littermates, the Arhgef10-depleted mice showed social interaction impairment, hyperactivity, and decreased depression-like and anxiety-like behavior. Behavioral measures of learning in the Morris water maze were not affected by Arhgef10 deficiency. Moreover, neurotransmitters including serotonin, norepinephrine, and dopamine were significantly increased in different brain regions of the Arhgef10 knockout mice. In addition, monoamine oxidase A (MAO-A) decreased in several brain regions.

Conclusions

These results suggest that ARHGEF10 is a candidate risk gene for ASD and that the Arhgef10 knockout model could be a tool for studying the mechanisms of neurotransmission in ASD.

Trial registration

Animal studies were approved by the Institutional Animal Care and Use Committee of National Taiwan University (IACUC 20150023). Registered 1 August 2015.

Electronic supplementary material

The online version of this article (10.1186/s13229-018-0197-5) contains supplementary material, which is available to authorized users.

The number of neurons in specific amygdala regions is associated with boldness in mink: a study in animal personality

Conspecifics vary consistently in their behavioural responses towards environment stimuli such as exposure to novel objects; ethologists often refer to this variability as animal personality. The neurological mechanisms underlying animal personality traits remain largely unknown, but linking the individual variation in emotional expression to brain structural and neurochemical factors is attracting renewed interest. While considerable research has focused on hormonal and neurotransmitter effects on behavioural responses, less is known about how individual variation in the number of specific neuron populations contributes to individual variation in behaviour. The basolateral amygdala (BLA) and the central nuclei of the amygdala (CeA) mediate emotional processing by regulating behavioural responses of animals in a potentially threatening situation. As such, these structures are good candidates for evaluating the relationship between neuronal populations and behavioural traits. We now show that individual American mink (Neovison vison) reacting more boldly towards novelty have more neurons in the BLA than do their more timid conspecifics, suggesting that a developmental pattern of the number of amygdala neurons can influence behavioural traits of an adult animal. Furthermore, post hoc correlations revealed that individuals performing with higher arousal, as reflected by their frequency of startle behaviour, have more CeA neurons. Our results support a direct link between the number of neurons in amygdala regions and aspects of animal personality.

Lithium monotherapy associated clinical improvement effects on amygdala-ventromedial prefrontal cortex resting state connectivity in bipolar disorder

BACKGROUND

This study, for the first time, investigated lithium monotherapy associated effects on amygdala- ventromedial prefrontal cortex (vMPFC) resting-state functional connectivity and correlation with clinical improvement in bipolar disorder (BP) METHODS: Thirty-six medication-free subjects - 24 BP (12 hypomanic BPM) and 12 depressed (BPD)) and 12 closely matched healthy controls (HC), were included. BP subjects were treated with lithium and scanned at baseline, after 2 weeks and 8 weeks. HC were scanned at same time points but were not treated. The effect of lithium was studied for the BP group as a whole using two way (group, time) ANOVA while regressing out effects of state. Next, correlation between changes in amygdala-vMPFC resting-state connectivity and clinical global impression (CGI) of severity and improvement scale scores for overall BP illness was calculated. An exploratory analysis was also conducted for the BPD and BPM subgroups separately.

RESULTS

Group by time interaction revealed that lithium monotherapy in patients was associated with increase in amygdala-medial OFC connectivity after 8 weeks of treatment (p = 0.05 (cluster-wise corrected)) compared to repeat testing in healthy controls. Increased amygdala-vMPFC connectivity correlated with clinical improvement at week 2 and week 8 as measured with the CGI-I scale.

LIMITATIONS

The results pertain to open-label treatment and do not account for non-treatment related improvement effects. Only functional connectivity was measured which does not give information regarding one regions effect on the other.

CONCLUSIONS

Lithium monotherapy in BP is associated with modulation of amygdala-vMPFC connectivity which correlates with state-independent global clinical improvement.

Social Origins of Developmental Risk for Mental and Physical Illness

Adversity in early childhood exerts an enduring impact on mental and physical health, academic achievement, lifetime productivity, and the probability of interfacing with the criminal justice system. More science is needed to understand how the brain is affected by early life stress (ELS), which produces excessive activation of stress response systems broadly throughout the child's body (toxic stress). Our research examines the importance of sex, timing and type of stress exposure, and critical periods for intervention in various brain systems across species. Neglect (the absence of sensitive and responsive caregiving) or disrupted interaction with offspring induces robust, lasting consequences in mice, monkeys, and humans. Complementary assessment of internalizing disorders and brain imaging in children suggests that early adversity can interfere with white matter development in key brain regions, which may increase risk for emotional difficulties in the long term. Neural circuits that are most plastic during ELS exposure in monkeys sustain the greatest change in gene expression, offering a mechanism whereby stress timing might lead to markedly different long-term behaviors. Rodent models reveal that disrupted maternal-infant interactions yield metabolic and behavioral outcomes often differing by sex. Moreover, ELS may further accelerate or delay critical periods of development, which reflect GABA circuit maturation, BDNF, and circadian Clock genes. Such factors are associated with several mental disorders and may contribute to a premature closure of plastic windows for intervention following ELS. Together, complementary cross-species studies are elucidating principles of adaptation to adversity in early childhood with molecular, cellular, and whole organism resolution.

Protracted dendritic growth in the typically developing human amygdala and increased spine density in young ASD brains

The amygdala is a medial temporal lobe structure implicated in social and emotional regulation. In typical development (TD), the amygdala continues to increase volumetrically throughout childhood and into adulthood, while other brain structures are stable or decreasing in volume. In autism spectrum disorder (ASD), the amygdala undergoes rapid early growth, making it volumetrically larger in children with ASD compared to TD children. Here we explore: (a) if dendritic arborization in the amygdala follows the pattern of protracted growth in TD and early overgrowth in ASD and (b), if spine density in the amygdala in ASD cases differs from TD from youth to adulthood. The amygdala from 32 postmortem human brains (7-46 years of age) were stained using a Golgi-Kopsch impregnation. Ten principal neurons per case were selected in the lateral nucleus and traced using Neurolucida software in their entirety. We found that both ASD and TD individuals show a similar pattern of increasing dendritic length with age well into adulthood. However, spine density is (a) greater in young ASD cases compared to age-matched TD controls (<18 years old) and (b) decreases in the amygdala as people with ASD age into adulthood, a phenomenon not found in TD. Therefore, by adulthood, there is no observable difference in spine density in the amygdala between ASD and TD age-matched adults (≥18 years old). Our findings highlight the unique growth trajectory of the amygdala and suggest that spine density may contribute to aberrant development and function of the amygdala in children with ASD.

Oxytocin Removes Estrous Female vs. Male Preference of Virgin Male Rats: Mediation of the Supraoptic Nucleus Via Olfactory Bulbs

Social functions of oxytocin (OT) have been explored extensively; however, relationship between the effect of intranasally applied OT (nasal OT) on the social preference (SP) and intracerebral actions of endogenous OT remains unclear. To resolve this question, we first observed effects of nasal OT on the SP of virgin young adult male rats toward unfamiliar virgin estrous female (EF) vs. virgin male rats. The results showed that the test male rats exhibited significantly more times and longer duration accessing the female than the male, which were acutely eliminated by nasal OT. Then, we examined the approaches mediating nasal OT effects on the activity of potential brain targets in Western blots and found that nasal OT activated the olfactory bulbs (OBs) and the supraoptic nucleus (SON), but not the piriform cortex, amygdala and hippocampus as shown by significant changes in the expression of c-Fos and/or phosphorylated extracellular signal-regulated protein kinase (pERK) 1/2. Moreover, microinjection of TTX into the OBs blocked nasal OT-evoked increases in pERK1/2 levels as well as the molecular association between ERK1/2 and OT-neurophysin in the SON. Electrolytic lesions of the lateral olfactory tract did not significantly change the basal levels of pERK 1/2 in the SON; however, upon nasal OT, pERK 1/2 levels in the SON reduced significantly. Lastly, microinjection of L-aminoadipic acid (gliotoxin) into the SON to reduce OT levels reduced the duration of the test male’s accessing the EF and blocked the nasal OT-evoked increase in the duration of test male’s accessing the male while significantly increasing pERK1/2 levels in the amygdala. These findings reveal for the first time that nasal OT acutely eliminates virgin males’ SP to EFs via the OB-SON route and that OT neurons could mediate the social effects of nasal OT by suppressing social phobia generated in the amygdala.

Genetic deletion of P-glycoprotein alters stress responsivity and increases depression-like behavior, social withdrawal and microglial activation in the hippocampus of female mice

P-glycoprotein (P-gp) is an ABC transporter expressed at the blood brain barrier and regulates the brain uptake of various xenobiotics and endogenous mediators including glucocorticoid hormones which are critically important to the stress response. Moreover, P-gp is expressed on microglia, the brain's immune cells, which are activated by stressors and have an emerging role in psychiatric disorders. We therefore hypothesised that germline P-gp deletion in mice might alter the behavioral and microglial response to stressors. Female P-gp knockout mice displayed an unusual, frantic anxiety response to intraperitoneal injection stress in the light-dark test. They also tended to display reduced conditioned fear responses compared to wild-type (WT) mice in a paradigm where a single electric foot-shock stressor was paired to a context. Foot-shock stress reduced social interaction and decreased microglia cell density in the amygdala which was not varied by P-gp genotype. Independently of stressor exposure, female P-gp deficient mice displayed increased depression-like behavior, idiosyncratic darting behavior, age-related social withdrawal and hyperactivity, facilitated sensorimotor gating and altered startle reactivity. In addition, P-gp deletion increased microglia cell density in the CA3 region of the hippocampus, and the microglial cells exhibited a reactive, hypo-ramified morphology. Further, female P-gp KO mice displayed increased glucocorticoid receptor (GR) expression in the hippocampus. In conclusion, this research shows that germline P-gp deletion affected various behaviors of relevance to psychiatric conditions, and that altered microglial cell activity and enhanced GR expression in the hippocampus may play a role in mediating these behaviors.

Increased GABAA receptor binding in amygdala after prenatal administration of valproic acid to rats

OBJECTIVE

Prenatal exposure to valproic acid (VPA) enhances the risk for later development of autism spectrum disorders (ASD). An altered gamma-aminobutyric acid (GABA) system may be a key factor in ASD. Here we investigated possible changes in the GABA system in rats exposed to a low dose of prenatal VPA.

METHOD

We performed autoradiography with [3H]muscimol, (a GABAA receptor agonist), and [11C]Ro15-4513 (a partial agonist of the GABAA α1+5 receptor subtypes), in brain sections containing amygdala, thalamus and hippocampus of rats treated prenatally with 20 mg/kg VPA or saline from the 12th day of gestation. Result Prenatal VPA significantly increased [11C]Ro15-4513 binding in the left amygdala compared with controls (p<0.05). This difference was not observed in the hippocampus, thalamus or right amygdala. No differences were observed in [3H]muscimol binding.

CONCLUSION

We observed an asymmetric increase in GABAA receptor binding. Disturbances in the GABAA receptor system have also been detected in human autism with [11C]Ro15-4513.

Genistein alleviates anxiety-like behaviors in post-traumatic stress disorder model through enhancing serotonergic transmission in the amygdala

Post-traumatic stress disorder (PTSD) is a chronic psychiatric disorder, characterized by intense fear, and increased arousal and avoidance of traumatic events. The current available treatments for PTSD have limited therapeutic value. Genistein, a natural isoflavone, modulates a variety of cell functions. In this study, we tested anti-anxiety activity and underlying mechanisms of genistein in a PTSD rat model. The rats were trained to associate a tone with foot shock delivery on day 0, then fear conditioning was performed on day 7, 14 and 21. Genistein (2-8mg/kg) was injected intraperitoneally daily for 7 days. The anti-anxiety effects of genistein were measured by contextual freezing behavior and elevated plus maze. By the end of the experiments, the amygdala was extracted and subject to neurochemistry analysis. Genistein alleviated contextual freezing behavior and improved performance in elevated plus maze dose-dependently in PTSD rats. Furthermore, in these rats, genistein enhanced serotonergic transmission in the amygdala, including upregulation of tryptophan hydroxylase, serotonin, and phosphorylated (p)-CaMKII and p-CREB, as well. Genistein exerts anti-anxiety effects on a PTSD model probably through enhancing serotonergic system and CaMKII/CREB signaling pathway in the amygdala.

Elucidation of White Matter Tracts of the Human Amygdala by Detailed Comparison between High-Resolution Postmortem Magnetic Resonance Imaging and Histology

The amygdala has attracted considerable research interest because of its potential involvement in various neuropsychiatric disorders. Recently, attempts have been made using magnetic resonance imaging (MRI) to evaluate the integrity of the axonal connections to and from the amygdala under pathological conditions. Although amygdalar pathways have been studied extensively in animal models, anatomical references for the human brain are limited to histology-based resources from a small number of slice locations, orientations and annotations. In the present study, we performed high-resolution (250 μm) MRI of postmortem human brains followed by serial histology sectioning. The histology data were used to identify amygdalar pathways, and the anatomical delineation of the assigned structures was extended into 3D using the MRI data. We were able to define the detailed anatomy of the stria terminalis and amygdalofugal pathway, as well as the anatomy of the nearby basal forebrain areas, including the substantia innominata. The present results will help us understand in detail the white matter structures associated with the amygdala, and will serve as an anatomical reference for the design of in vivo MRI studies and interpretation of their data.