The amygdala as a hub in brain networks that support social life

Lesions of the rat basolateral amygdala reduce the behavioral response to ultrasonic vocalizations

Rats emit vocalizations in the ultrasonic range (ultrasonic vocalizations; USVs), of which 50-kHz USVs could communicate positive affective states and induce approach behavior in conspecifics, whereas 22-kHz USVs might signal negative affective states and potential threats. Listening to 50-kHz USVs can be rewarding, but it is unknown which brain mechanisms are responsible for the assignment of reinforcing value to 50-kHz USVs . The behavioral responses induced by listening to 22-kHz USVs are heterogeneous and need further characterization. The amygdala is a region relevant for social perception, behavior and reward. Here, we tested the hypothesis that the basolateral amygdala (BLA) plays a causal role in motivating behavioral responses to 50-kHz and 22-kHz USVs. Rats with lesions of the BLA or sham lesions were repeatedly exposed to playback of either 50-kHz or 22-kHz USVs in a radial maze. Compared to sham rats, BLA-lesioned rats spent less time in the arms close to the USV speaker during playback of both 50-kHz or 22-kHz USVs. This difference in behavior was not due to impaired motor or general auditory abilities, indicating that BLA lesions selectively reduced the responsiveness to stimuli with social significance. This finding provides further support for the hypothesis that the BLA plays an important role in motivating approach behavior to social reinforcers.

Topology of the Structural Social Brain Network in Typical Adults

Although a large body of research has identified discrete neuroanatomical regions involved in social cognition and behavior (the "social brain"), the existing findings are based largely on studies of specific brain structures defined within the context of particular tasks or for specific types of social behavior. The objective of the current work was to view these regions as nodes of a larger collective network and to quantitatively characterize both the topology of that network and the relative criticality of its many nodes. Large-scale data mining was performed to generate seed regions of the social brain. High-quality diffusion MRI data of typical adults were used to map anatomical networks of the social brain. Network topology and nodal centrality were analyzed using graph theory. The structural social brain network demonstrates a high degree of global functional integration with strong local segregation. Bilateral dorsomedial prefrontal cortices and amygdala play the most central roles in the network. Strong probabilistic evidence supports modular divisions of the social brain into subnetworks bearing good resemblance to functionally classified clusters. The present network-driven approach quantifies the structural topology of the social brain as a whole. This work can serve as a critical benchmark against which to compare (1) developmental change in social brain topology over time (from infancy through adolescence and beyond) and (2) atypical network topologies that may be a sign or symptom of disorder (as in conditions such as autism, Williams syndrome, schizophrenia, and others).

Peripheral and central compensatory mechanisms for impaired vagus nerve function during peripheral immune activation

BACKGROUND

Determining the etiology and possible treatment strategies for numerous diseases requires a comprehensive understanding of compensatory mechanisms in physiological systems. The vagus nerve acts as a key interface between the brain and the peripheral internal organs. We set out to identify mechanisms compensating for a lack of neuronal communication between the immune and the central nervous system (CNS) during infection.

METHODS

We assessed biochemical and central neurotransmitter changes resulting from subdiaphragmatic vagotomy and whether they are modulated by intraperitoneal infection. We performed a series of subdiaphragmatic vagotomy or sham operations on male Wistar rats. Next, after full, 30-day recovery period, they were randomly assigned to receive an injection of Escherichia coli lipopolysaccharide or saline. Two hours later, animal were euthanized and we measured the plasma concentration of prostaglandin E2 (with HPLC-MS), interleukin-6 (ELISA), and corticosterone (RIA). We also had measured the concentration of monoaminergic neurotransmitters and their metabolites in the amygdala, brainstem, hippocampus, hypothalamus, motor cortex, periaqueductal gray, and prefrontal medial cortex using RP-HPLC-ED. A subset of the animals was evaluated in the elevated plus maze test immediately before euthanization.

RESULTS

The lack of immunosensory signaling of the vagus nerve stimulated increased activity of discrete inflammatory marker signals, which we confirmed by quantifying biochemical changes in blood plasma. Behavioral results, although preliminary, support the observed biochemical alterations. Many of the neurotransmitter changes observed after vagotomy indicated that the vagus nerve influences the activity of many brain areas involved in control of immune response and sickness behavior. Our studies show that these changes are largely eliminated during experimental infection.

CONCLUSIONS

Our results suggest that in vagotomized animals with blocked CNS, communication may transmit via a pathway independent of the vagus nerve to permit restoration of CNS activity for peripheral inflammation control.

Age-Related Structural Alterations in Human Amygdala Networks: Reflections on Correlations Between White Matter Structure and Effective Connectivity

The amygdala, which is involved in human social information processing and socio-emotional response neuronal circuits, is segmented into three subregions that are responsible for perception, affiliation, and aversion. Though there is different functional and effective connectivity (EC) among these networks, age-related structural changes and associations between structure and function within the amygdala remain unclear. Here, we used diffusion tensor imaging (DTI) data (106 participants) to investigate age-related structural changes in fractional anisotropy (FA) of amygdalar subregions. We also examined the relationship between FA and EC within the subregions. We found that the FA of the amygdalar subregions exhibited inverted-U-shape trends with age. Moreover, over the human lifespan, there were negative correlations between the FA of the right ventrolateral amygdala (VLA.R) and the Granger-based EC (GC) of VLA.R → perception network (PerN), the FA of the VLA.R and the GC of the net flow from VLA.R → PerN, and the FA of the left dorsal amygdala (DorA.L) and the GC of the aversion network (AveN). Conversely, there was a positive correlation between the FA of the DorA.L and the GC of the net flow from DorA.L → AveN. Our results suggest that age-related changes in the function of the brain are constrained by the underlying white matter architectures, while the functional information flow changes influence white matter structure. This work increases our understanding of the neuronal mechanisms in the maturation and aging process.

Dynamics and diversity of heart rate responses to a disaster motion picture

Emotions are dynamic neuropsychophysiological processes that guide behavior and serve as crucial signals during social interactions. Measuring their highly individual temporal dynamics is an unresolved challenge, but the coupling of autonomic and central nervous processes offers a promising approach. We present a feasible approach to study changes in heart rate during emotions and demonstrate a link to empathy. We investigated the interindividual similarity and temporal dynamics of heart rate responses to an emotive motion picture. Forty healthy participants watched "The Impossible" (109 min; Hermida Muñiz et al., 2012) while their heart rate was recorded. Interindividual concordance of heart rate responses was analysed using agglomerative hierarchical clustering analyses to distinguish response patterns throughout the movie and during six highly emotive scenes. This revealed multiple response patterns during emotive scenes. Second, we analysed how changes in heart rate are linked to self-reported empathy. We found that the extent of changes in heart rate is positively linked to trait and state empathy. During specific scenes, this relationship was only visible when individuals with homogeneous heart rate response patterns were observed, but not across discordant response patterns. In conclusion, our results demonstrate that heart rate responses to complex social stimuli are not uniform. Therefore, research should favour statistical procedures with the potential to detect interindividual differences. The approach presented in our study allows us to depict interindividual similarity and diversity in emotional autonomic responses and emphasizes the key role of empathy in emotional experiences.

Neural processing of social interaction: Coordinate-based meta-analytic evidence from human neuroimaging studies

While the action observation and mentalizing networks are considered to play complementary roles in understanding others' goals and intentions, they might be concurrently engaged when processing social interactions. We assessed this hypothesis via three activation-likelihood-estimation meta-analyses of neuroimaging studies on the neural processing of: (a) social interactions, (b) individual actions by the action observation network, and (c) mental states by the mentalizing network. Conjunction analyses and direct comparisons unveiled overlapping and specific regions among the resulting maps. We report quantitative meta-analytic evidence for a "social interaction network" including key nodes of the action observation and mentalizing networks. An action-social interaction-mentalizing gradient of activity along the posterior temporal cortex highlighted a hierarchical processing of interactions, from visuomotor analyses decoding individual and shared intentions to in-depth inferences on actors' intentional states. The medial prefrontal cortex, possibly in conjunction with the amygdala, might provide additional information concerning the affective valence of the interaction. This evidence suggests that the functional architecture underlying the neural processing of interactions involves the joint involvement of the action observation and mentalizing networks. These data might inform the design of rehabilitative treatments for social cognition disorders in pathological conditions, and the assessment of their outcome in randomized controlled trials.

Severity of anxiety moderates the association between neural circuits and maternal behaviors in the postpartum period

Neuroimaging research has suggested that activity in the amygdala, center of the socioemotional network, and functional connectivity between the amygdala and cortical regions are associated with caregiving behaviors in postpartum mothers. Anxiety is common in the early postpartum period, with severity ranging from healthy maternal preoccupation to clinical disorder. However, little is known about the influence of anxiety on the neural correlates of early caregiving. We examined these relationships in a community cohort of 75 postpartum women (ages 18-22; predominantly low-SES, minority race) who listened to infant cry sounds while undergoing an fMRI assessment. Maternal self-reported symptoms of anxiety were mostly within the subclinical range. Positive and negative caregiving behaviors during filmed face-to-face mother-infant interactions were coded by independent observers. The results from whole-brain analyses showed that anxiety severity moderated the brain-maternal behavior relationships. Specifically, our results showed that the higher a mother's anxiety, the stronger the association between positive caregiving (i.e., maternal warmth and involvement) and amygdala-right posterior superior temporal sulcus (amygdala-RpSTS) functional connectivity. These results remained significant when we controlled for symptoms of depression and contextual variables. These findings suggest that functional connectivity between the amygdala and a social perception region (RpSTS) plays a particularly important role for anxious mothers in facilitating their positive parenting. These findings extend our understanding of the specific neural circuits that support positive maternal caregiving in the context of maternal anxiety, and they may help inform the future design of personalized and effective interventions.

Association of OXTR rs53576 with the Developmental Trajectories of Callous-Unemotional Traits and Stressful Life Events in 3- to 9-Year-Old Community Children

The objective was to obtain developmental trajectories combining callous-unemotional traits and the number of stressful life-events between ages 3 and 9 years and to ascertain their association with the polymorphism rs53576 at the Oxytocin Receptor gene (OXTR). A total of 377 children were assessed yearly from ages 3 to 9 years. Latent class growth analysis for parallel processes was used to identify distinct trajectories for callous-unemotional traits (assessed using the Inventory of Callous-Unemotional Traits, ICU) and number of stressful life-events, and then the influence of being an A allele carrier on class membership was included with OXTR genotypes as a binary time-invariant predictor, following a 3-step approach. A 3-class model showed the highest entropy (.859) and adequate posterior probabilities of class membership (≥.884). Class 1 (n = 226, 59.9%) included children with low and stable ICU scores and low and descending stressful life-events; class 2 (n = 127, 33.7%) included children with high and ascending ICU scores and low and slightly descending stressful life-events; and class 3 (n = 24, 6.4%) included children with persistently high profiles both for ICU scores and stressful life-events. Carrying an A allele (genotypes GA/AA) increased the odds of pertaining to class 3 (high and persistent ICU scores and stressful life-events) as opposed to class 2 (OR = 4.27, p = 0.034) or class 1 (OR = 3.81, p = 0.042). The results suggest the importance of considering callous-unemotional traits and stressful life-events in conjunction. In addition, the genetic variability of OXTR (rs53576) may help to understand individual differences in early development.

Music enhances activity in the hypothalamus, brainstem, and anterior cerebellum during script-driven imagery of affective scenes

Music is frequently used to establish atmosphere and to enhance/alter emotion in dramas and films. During music listening, visual imagery is a common mechanism underlying emotion induction. The present functional magnetic resonance imaging (fMRI) study examined the neural substrates of the emotional processing of music and imagined scene. A factorial design was used with factors emotion valence (positive; negative) and music (withoutMUSIC: script-driven imagery of emotional scenes; withMUSIC: script-driven imagery of emotional scenes and simultaneously listening to affectively congruent music). The baseline condition was imagery of neutral scenes in the absence of music. Eleven females and five males participated in this fMRI study. Behavioural data revealed that during scene imagery, participants' subjective emotions were significantly intensified by music. The contrasts of positive and negative withoutMUSIC conditions minus the baseline (imagery of neutral scenes) showed no significant activation. When comparing the withMUSIC to withoutMUSIC conditions, activity in a number of emotion-related regions was observed, including the temporal pole (TP), amygdala, hippocampus, hypothalamus, anterior ventral tegmental area (VTA), locus coeruleus, and anterior cerebellum. We hypothesized that the TP may integrate music and the imagined scene to extract socioemotional significance, initiating the subcortical structures to generate subjective feelings and bodily responses. For the withMUSIC conditions, negative emotions were associated with enhanced activation in the posterior VTA compared to positive emotions. Our findings replicated and extended previous research which suggests that different subregions of the VTA are sensitive to rewarding and aversive stimuli. Taken together, this study suggests that emotional music embedded in an imagined scenario is a salient social signal that prompts preparation of approach/avoidance behaviours and emotional responses in listeners.

Beyond Emotions: Oscillations of the Amygdala and Their Implications for Electrical Neuromodulation

The amygdala is a structure involved in emotions, fear, learning and memory and is highly interconnected with other brain regions, for example the motor cortex and the basal ganglia that are often targets of treatments involving electrical stimulation. Deep brain stimulation of the basal ganglia is successfully used to treat movement disorders, but can carry along non-motor side effects. The origin of these non-motor side effects is not fully understood yet, but might be altered oscillatory communication between specific motor areas and the amygdala. Oscillations in various frequency bands have been detected in the amygdala during cognitive and emotional tasks, which can couple with oscillations in cortical regions or the hippocampus. However, data on oscillatory coupling between the amygdala and motor areas are still lacking. This review provides a summary of oscillation frequencies measured in the amygdala and their possible functional relevance in different species, followed by evidence for connectivity between the amygdala and motor areas, such as the basal ganglia and the motor cortex. We hypothesize that the amygdala could communicate with motor areas through coherence of low frequency bands in the theta-alpha range. Furthermore, we discuss a potential role of the amygdala in therapeutic approaches based on electrical stimulation.

Connectivity-Based Parcellation of the Amygdala Predicts Social Skills in Adolescents with Autism Spectrum Disorder

Amygdala dysfunction plays a role in the social impairments in autism spectrum disorders (ASD), but it is unclear which of its subregions are abnormal in ASD. This study compared the volume and functional connectivity (FC) strength of three FC-defined amygdala subregions between ASD and controls, and assessed their relation to social skills in ASD. A subregion associated with the social perception network was enlarged in ASD (F₁ = 7.842, p = .008) and its volume correlated significantly with symptom severity (social skills: r = .548, p = .009). Posthoc analysis revealed that the enlargement was driven by the vmPFC amygdala network. These findings refine our understanding of abnormal amygdala connectivity in ASD and may inform future strategies for therapeutic interventions targeting the amygdalofrontal pathway.

Causal Interactions in Human Amygdala Cortical Networks across the Lifespan

There is growing evidence that the amygdala serves as the base for dealing with complex human social communication and emotion. Although amygdalar networks plays a central role in these functions, causality connectivity during the human lifespan between amygdalar subregions and their corresponding perception network (PerN), affiliation network (AffN) and aversion network (AveN) remain largely unclear. Granger causal analysis (GCA), an approach to assess directed functional interactions from time series data, was utilized to investigated effective connectivity between amygdalar subregions and their related networks as a function of age to reveal the maturation and degradation of neural circuits during development and ageing in the present study. For each human resting functional magnetic resonance imaging (fMRI) dataset, the amygdala was divided into three subareas, namely ventrolateral amygdala (VLA), medial amygdala (MedA) and dorsal amygdala (DorA), by using resting-state functional connectivity, from which the corresponding networks (PerN, AffN and AveN) were extracted. Subsequently, the GC interaction of the three amygdalar subregions and their associated networks during life were explored with a generalised linear model (GLM). We found that three causality flows significantly varied with age: the GC of VLA → PerN showed an inverted U-shaped trend with ageing; the GC of MedA→ AffN had a U-shaped trend with ageing; and the GC of DorA→ AveN decreased with ageing. Moreover, during ageing, the above GCs were significantly correlated with Social Responsiveness Scale (SRS) and State-Trait Anxiety Inventory (STAI) scores. In short, PerN, AffN and AveN associated with the amygdalar subregions separately presented different causality connectivity changes with ageing. These findings provide a strong constituent framework for normal and neurological diseases associated with social disorders to analyse the neural basis of social behaviour during life.

Oxytocin modulates social value representations in the amygdala

Humans exhibit considerable variation in how they value their own interest relative to the interests of others. Deciphering the neural codes representing potential rewards for self and others is crucial for understanding social decision-making. Here we integrate computational modeling with functional magnetic resonance imaging to investigate the neural representation of social value and the modulation by oxytocin, a nine-amino acid neuropeptide, in participants evaluating monetary allocations to self and other (self-other allocations). We found that an individual's preferred self-other allocation serves as a reference point for computing the value of potential self-other allocations. In more prosocial participants, amygdala activity encoded a social-value-distance signal; that is, the value dissimilarity between potential and preferred allocations. Intranasal oxytocin administration amplified this amygdala representation and increased prosocial behavior in more individualistic participants but not in more prosocial ones. Our results reveal a neurocomputational mechanism underlying social-value representations and suggest that oxytocin may promote prosociality by modulating social-value representations in the amygdala.

Amygdala functional network during recognition of own-age vs. other-age faces in younger and older adults

Facial cues, such as a person's age, provide important information for social interactions. Processing such facial cues can be affected by observer bias. However, there is currently no consensus regarding how the brain is processing facial cues related to age, and if facial age processing changes as a function of the age of the observer (i.e., own-age bias). The primary study aim was to investigate functional networks involved in processing own-age vs. other-age faces among younger and older adults and determine how emotional expression of the face modulates own-age vs. other-age face processing. The secondary study aim was to examine the relation between higher social cognitive processes (i.e., empathy) and modulation of brain activity by facial age and emotional expression. During functional magnetic resonance imaging (fMRI) younger and older participants were asked to recognize happy, angry, and neutral expressions in own-age and other-age faces. Functional connectivity analyses with the amygdala as seed showed that for own-age faces both age groups recruited a network of regions including the anterior cingulate and anterior insula that was involved in empathy and detection of salient information. Brain-behavior analyses furthermore showed that empathic responses in younger, but not in older, participants were positively correlated with engagement of the medial prefrontal cortex during processing of angry own-age faces. These findings identify the neurobehavioral correlates of facial age processing, and its modulation by emotion expression, and directly link facial cue processing to higher-order social cognitive functioning.

A double-blind HD-tDCS/EEG study examining right temporoparietal junction involvement in facial emotion processing

Prior studies have demonstrated that aspects of social cognition can be modulated via temporoparietal junction (TPJ) transcranial direct current stimulation (tDCS). However, this technique lacks focality and electrophysiological effects or correlates are rarely examined. The present study investigated whether anodal and/or cathodal high-definition tDCS (HD-tDCS) would influence facial emotion processing performance relative to sham stimulation, and whether task performance changes were related to neurophysiological changes. Participants completed a facial emotion attribution tasks before and after rTPJ HD-tDCS, with event-related potentials (ERP) recorded during task performance. Anodal rTPJ HD-tDCS improved facial emotion processing performance for static depictions of fear (but not surprise). Stimulation condition influenced P300 latency, and also influenced the relationship between behavioural and electrophysiological (ERP) outcomes in several circumstances, findings which both support and challenge anodal-excitation/cathodal-inhibition accounts of tDCS effects. Results suggest that rTPJ anodal HD-tDCS can influence facial emotion recognition (i.e., affective mentalizing), and elucidate the nature and distribution of underlying neurophysiological processes. Stimulation effects, however, might depend on the intensity and salience/valence (negativity/threat) of the emotion, and these behavioural effects may not relate directly or simply to the ERPs assessed here.

Oxytocin alters patterns of brain activity and amygdalar connectivity by age during dynamic facial emotion identification

Aging is associated with increased difficulty in facial emotion identification, possibly due to age-related network change. The neuropeptide oxytocin (OT) facilitates emotion identification, but this is understudied in aging. To determine the effects of OT on dynamic facial emotion identification across adulthood, 46 young and 48 older participants self-administered intranasal OT or a placebo in a randomized, double-blind procedure. Older participants were slower and less accurate in identifying emotions. Although there was no behavioral treatment effect, partial least squares analysis supported treatment effects on brain patterns during emotion identification that varied by age and emotion. For young participants, OT altered the processing of sadness and happiness, whereas for older participants, OT only affected the processing of sadness (15.3% covariance, p = 0.004). Furthermore, seed partial least squares analysis showed that older participants in the OT group recruited a large-scale amygdalar network that was positively correlated for anger, fear, and happiness, whereas older participants in the placebo group recruited a smaller, negatively correlated network (7% covariance, p = 0.002). Advancing the literature, these findings show that OT alters brain activity and amygdalar connectivity by age and emotion.

Social Memory and Social Patterns Alterations in the Absence of STriatal-Enriched Protein Tyrosine Phosphatase

STriatal-Enriched protein tyrosine Phosphatase (STEP) is a neural-specific protein that opposes the development of synaptic strengthening and whose levels are altered in several neurodegenerative and psychiatric disorders. Since STEP is expressed in brain regions implicated in social behavior, namely the striatum, the CA2 region of the hippocampus, cortex and amygdala, here we investigated whether social memory and social patterns were altered in STEP knockout (KO) mice. Our data robustly demonstrated that STEP KO mice presented specific social memory impairment as indicated by the three-chamber sociability test, the social discrimination test, the 11-trial habituation/dishabituation social recognition test, and the novel object recognition test (NORT). This affectation was not related to deficiencies in the detection of social olfactory cues, altered sociability or anxiety levels. However, STEP KO mice showed lower exploratory activity, reduced interaction time with an intruder, less dominant behavior and higher immobility time in the tail suspension test than controls, suggesting alterations in motivation. Moreover, the extracellular levels of dopamine (DA), but not serotonin (5-HT), were increased in the dorsal striatum of STEP KO mice. Overall, our results indicate that STEP deficiency disrupts social memory and other social behaviors as well as DA homeostasis in the dorsal striatum.

Structural covariability hubs in old age

Studies have shown that inter-individual differences in grey matter, as measured by voxel-based morphometry, are coordinated between voxels. This has been done by studying covariance maps based on a limited number of seed regions. Here, we used GPU-based (Graphics Processing Unit) accelerated computing to calculate, for the first time, the aggregated map of the total structural topographical organisation in the brain on voxel level in a large sample of 960 healthy individuals in the age range 68-83 years. This map describes for each voxel the number of significant correlations with all other grey matter voxels in the brain. Voxels that correlate significantly with many other voxels are called hubs. A majority of these hubs were found in the basal ganglia, the thalamus, the brainstem, and the cerebellum; subcortical regions that have been preserved through vertebrate evolution, interact with large portions of the neocortex and play fundamental roles for the control of a wide range of behaviours. No significant difference in the level of covariability could be found with increasing age or between men and women in these hubs.

Residential green and blue space associated with better mental health: a pilot follow-up study in university students

Previous research has suggested that natural urban environment (green space and blue space) benefit mental health, but only a few longitudinal studies have explored the underlying mechanisms. In this pilot study we aimed to examine mechanisms/variables mediating associations between residential green/blue space and symptoms of anxiety/depression in 109 Bulgarian students from Plovdiv university. The students were followed from the beginning to the end of the school year (October 2017 to May 2018). Residential green space was defined as the mean of the normalised difference vegetation index (NDVI) in circular buffers of 100, 300, and 500 m around their residences. Blue space was assessed based on its presence in the same buffers. Levels of anxiety/depression were assessed using the 12-item General Health Questionnaire. The investigated mediator variables included residential noise (LAeq) and air pollution (NO2), environmental annoyance, perceived restorative quality of the neighbourhood, neighbourhood social cohesion, physical activity, and sleep disturbance. Cross-sectional data (obtained at baseline) showed that higher NDVI correlated with better mental health only indirectly through higher physical activity and restorative quality. Longitudinal (follow-up) data showed improved mental health but no significant effect of mediator variables. Similarly, blue space correlated with better mental health in all models, but physical activity and restorative quality were significant mediator variables only in the cross-sectional analysis. Our findings support that green space and blue space are psychologically restorative features in urban environment. Future research should replicate these findings in the general population and employ longitudinal modelling tailored to the specific mechanisms under study.

Autism Pathogenesis: The Superior Colliculus

After been exposed to the visual input, in the first year of life, the brain experiences subtle but massive changes apparently crucial for communicative/emotional and social human development. Its lack could be the explanation of the very high prevalence of autism in children with total congenital blindness. The present theory postulates that the superior colliculus is the key structure for such changes for several reasons: it dominates visual behavior during the first months of life; it is ready at birth for complex visual tasks; it has a significant influence on several hemispheric regions; it is the main brain hub that permanently integrates visual and non-visual, external and internal information (bottom-up and top-down respectively); and it owns the enigmatic ability to take non-conscious decisions about where to focus attention. It is also a sentinel that triggers the subcortical mechanisms which drive social motivation to follow faces from birth and to react automatically to emotional stimuli. Through indirect connections it also activates simultaneously several cortical structures necessary to develop social cognition and to accomplish the multiattentional task required for conscious social interaction in real life settings. Genetic or non-genetic prenatal or early postnatal factors could disrupt the SC functions resulting in autism. The timing of postnatal biological disruption matches the timing of clinical autism manifestations. Astonishing coincidences between etiologies, clinical manifestations, cognitive and pathogenic autism theories on one side and SC functions on the other are disclosed in this review. Although the visual system dependent of the SC is usually considered as accessory of the LGN canonical pathway, its imprinting gives the brain a qualitatively specific functions not supplied by any other brain structure.

The Cerebellar Predictions for Social Interactions: Theory of Mind Abilities in Patients With Degenerative Cerebellar Atrophy

Recent studies have focused on the role of the cerebellum in the social domain, including in Theory of Mind (ToM). ToM, or the “mentalizing” process, is the ability to attribute mental states, such as emotion, intentions and beliefs, to others to explain and predict their behavior. It is a fundamental aspect of social cognition and crucial for social interactions, together with more automatic mechanisms, such as emotion contagion. Social cognition requires complex interactions between limbic, associative areas and subcortical structures, including the cerebellum. It has been hypothesized that the typical cerebellar role in adaptive control and predictive coding could also be extended to social behavior. The present study aimed to investigate the social cognition abilities of patients with degenerative cerebellar atrophy to understand whether the cerebellum acts in specific ToM components playing a role as predictive structure. To this aim, an ad hoc social cognition battery was administered to 27 patients with degenerative cerebellar pathology and 27 healthy controls. In addition, 3D T1-weighted and resting-state fMRI scans were collected to characterize the structural and functional changes in cerebello-cortical loops. The results evidenced that the patients were impaired in lower-level processes of immediate perception as well as in the more complex conceptual level of mentalization. Furthermore, they presented a pattern of GM reduction in cerebellar portions that are involved in the social domain such as crus I-II, lobule IX and lobule VIIIa. These areas showed decreased functional connectivity with projection cerebral areas involved in specific aspects of social cognition. These findings boost the idea that the cerebellar modulatory function on the cortical projection areas subtends the social cognition process at different levels. Particularly, regarding the lower-level processes, the cerebellum may act by implicitly matching the external information (i.e., expression of the eyes) with the respective internal representation to guarantee an immediate judgment about the mental state of others. Otherwise, at a more complex conceptual level, the cerebellum seems to be involved in the construction of internal models of mental processes during social interactions in which the prediction of sequential events plays a role, allowing us to anticipate the other person's behavior.

Social brain volume is associated with in-degree social network size among older adults

The social brain hypothesis proposes that large neocortex size evolved to support cognitively demanding social interactions. Accordingly, previous studies have observed that larger orbitofrontal and amygdala structures predict the size of an individual's social network. However, it remains uncertain how an individual's social connectedness reported by other people is associated with the social brain volume. In this study, we found that a greater in-degree network size, a measure of social ties identified by a subject's social connections rather than by the subject, significantly correlated with a larger regional volume of the orbitofrontal cortex, dorsomedial prefrontal cortex and lingual gyrus. By contrast, out-degree size, which is based on an individual's self-perceived connectedness, showed no associations. Meta-analytic reverse inference further revealed that regional volume pattern of in-degree size was specifically involved in social inference ability. These findings were possible because our dataset contained the social networks of an entire village, i.e. a global network. The results suggest that the in-degree aspect of social network size not only confirms the previously reported brain correlates of the social network but also shows an association in brain regions involved in the ability to infer other people's minds. This study provides insight into understanding how the social brain is uniquely associated with sociocentric measures derived from a global network.

Tourette Syndrome as a Disorder of the Social Decision Making Network

Tourette syndrome is a common neurodevelopmental disorder defined by the presence of tics, stereotyped involuntary movements and phonations. Considerable evidence points to developmental abnormalities of the basal ganglia as tic substrates. Basal ganglia dysfunction does not account for important features of Tourette syndrome, including its natural history, male predominance, and the characteristic quality and distribution of tics. The latter mainly involve eye, face, and head movements, in addition to a variety of simple to complex phonations. A major normal function of these movements, and of phonations as well, is social signaling. Many important species- and sex-specific stereotyped social behaviors are mediated by a phylogenetically conserved network of subcortical nuclei, the social behavior network (SBN). Some SBN nuclei are sexually dimorphic, and SBN function is modulated strongly by gonadal steroids. Recent studies indicate that the SBN meshes with the basal ganglia to form a larger network, the Social Decision Making Network (SDM; O'Connell and Hofmann [2011]). The SDM concept overlaps significantly with Holstege's (1993) model of an emotional motor system mediating socially relevant facial movements and phonations. Dopaminergic signaling within the basal ganglia component of the SDM may regulate social act motivation with the SBN component responsible for act expression. Developmental SDM abnormalities can explain all major Tourette syndrome features, including natural history, male predominance, the characteristic distribution of tics, and their stereotyped quality. Some data directly support this hypothesis. Tourette syndrome may be a disorder of social communication manifesting primarily as abnormal involuntary movements.

Amygdala functional connectivity is associated with social impairments in preterm born young adults

Survivors of preterm birth experience long-lasting behavioral problems characterized by increased risk of depression, anxiety, and impairments in social functioning. The amygdala is a key region for social functioning and alterations in amygdala structure and connectivity are thought to underlie social functioning deficits in many disorders, including preterm birth. However, functional connectivity of the amygdala and its association with social impairments is not well-studied in preterm participants (PTs). In a group of late adolescents born very PT (600–1250 g birth weight), measures of social and emotional development were examined using the Child Behavior Checklist (CBCL) administered at age 16 (66 term and 161 preterm participants), the Youth Self Report (YSR) administered at age 16 (56 term and 45 preterm participants), and the Vineland Adaptive Behavior Scales (VABS) administered at age 18 (71 term and 190 preterm participants). Amygdala functional connectivity was also examined using resting-state functional magnetic resonance imaging at age 20 (17 term and 19 preterm participants). By parent report, preterm-born adolescents demonstrate increased social impairment compared to their term-born peers. Amygdala connectivity is altered for those prematurely-born, and markers of social functioning correlate with altered amygdala-PCC connectivity. These findings add to knowledge regarding the developmental trajectory of amygdala connectivity in PT and suggest a possible neural underpinning for the well-characterized social impairment experienced by prematurely-born individuals.

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By parent report, preterm adolescents demonstrate increased social impairment.

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By self-report, preterm adolescents demonstrate no social impairment.

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Amygdalar connectivity is altered for those preterm young adults.

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Markers of social functioning correlate with altered amygdala-PCC connectivity.

Oxytocin and Prader-Willi Syndrome

In the chapter, we explore the relationship between the peptide hormone, oxytocin (OT), and behavioral and metabolic disturbances observed in the genetic disorder Prader-Willi Syndrome (PWS). Phenotypic and genotypic characteristics of PWS are described, as are the potential implications of an abnormal OT system with respect to neural development including the possible effects of OT dysfunction on interactions with other regulatory mediators, including neurotransmitters, neuromodulators, and hormones. The major behavioral characteristics are explored in the context of OT dysfunction, including hyperphagia, impulsivity, anxiety and emotion dysregulation, sensory processing and interoception, repetitive and restrictive behaviors, and dysfunctional social cognition. Behavioral overlaps with autistic spectrum disorders are discussed. The implications of OT dysfunction on the mechanisms of reward and satiety and their possible role in informing behavioral characteristics are also discussed. Treatment implications and future directions for investigation are considered.

No evidence for morphometric associations of the amygdala and hippocampus with the five-factor model personality traits in relatively healthy young adults

Despite the important functional role of the amygdala and hippocampus in socioemotional functioning, there have been limited adequately powered studies testing how the structure of these regions relates to putatively relevant personality traits such as neuroticism. Additionally, recent advances in MRI analysis methods provide unprecedented accuracy in measuring these structures and enable segmentation into their substructures. Using the new FreeSurfer amygdala and hippocampus segmentation pipelines with the full Human Connectome Project sample (N = 1105), the current study investigated whether the morphometry of these structures is associated with the five-factor model (FFM) personality traits in a sample of relatively healthy young adults. Drawing from prior findings, the following hypotheses were tested: 1) amygdala and hippocampus gray matter volume would be associated with neuroticism, 2) CA2/3 and dentate gyrus would account for the relationship of the hippocampus with neuroticism, and 3) amygdala gray matter volume would be inversely associated with extraversion. Exploratory analyses were conducted investigating potential associations between all of the FFM traits and the structure of the hippocampus and amygdala and their subregions. Despite some previous positive findings of whole amygdala and hippocampus with personality traits and related psychopathology (e.g., depression), the current results indicated no relationships between the any of the brain regions and the FFM personality traits. Given the large sample and utilization of sophisticated analytic methodology, the current study suggests no association of amygdala and hippocampus morphometry with major domains of personality.

Anterior Temporal Lobectomy Impairs Neural Classification of Body Emotions in Right Superior Temporal Sulcus and Reduces Emotional Enhancement in Distributed Brain Areas without Affecting Behavioral Classification

Humans with amygdalar lesions show proportional reductions of the emotional response to facial expressions in the fusiform face area as well as deficits in emotion recognition from facial expressions. While processing of bodily expressions shares many similarities with facial expressions, there is no substantial evidence that lesions of the amygdala result in similar behavioral and neural sequelae. We combined behavioral assessment with functional neuroimaging in a group of male and female humans with unilateral anterior temporal lobe (ATL) resections, including the amygdala (right: n = 10; left: n = 10) and 12 matched controls. The objective was to assess whether the amygdala is crucial for the recognition of body expressions and for modulatory effects on distant areas during perception of body expressions. The behavioral results revealed normal performance in both patient groups on emotion categorization of body expressions. The neuroimaging results showed that ATL patients displayed no enhanced activations in right fusiform body area and left extrastriate body area and that left ATL patients additionally displayed no enhanced activations in right posterior superior temporal sulcus and right extrastriate body area, respectively. Multivoxel pattern analysis revealed altered categorization capacity between emotional and neutral stimuli in right posterior superior temporal sulcus in right ATL patients. In addition, we also found emotional enhancement in frontal, parietal, occipital, and cingulate regions in controls. Together, our data show that the amygdala and ATLs are not necessary for recognition of dynamic body expressions, but suggest that amygdala lesions affect body emotion processing in distant brain areas.SIGNIFICANCE STATEMENT For humans, information from emotional expressions of others is crucial to support social interactions. The majority of emotion studies has focused on facial expressions; however, in daily life, we also use information from body postures and body movement. Visual processing of body expressions relies on a brain network, including body-specific visual areas and visuomotor areas. Even though the importance of the amygdala and its modulatory effects on distant brain regions have been documented, it remains unclear whether the amygdala plays a crucial role in emotional body processing. By combining behavioral and neuroimaging data in patients with amygdalar lesions, we provide further evidence for its modulatory effect on distant areas during the perception of body expressions.

Social Cognition through the Lens of Cognitive and Clinical Neuroscience

Social cognition refers to a set of processes, ranging from perception to decision-making, underlying the ability to decode others' intentions and behaviors to plan actions fitting with social and moral, besides individual and economic considerations. Its centrality in everyday life reflects the neural complexity of social processing and the ubiquity of social cognitive deficits in different pathological conditions. Social cognitive processes can be clustered in three domains associated with (a) perceptual processing of social information such as faces and emotional expressions (social perception), (b) grasping others' cognitive or affective states (social understanding), and (c) planning behaviors taking into consideration others', in addition to one's own, goals (social decision-making). We review these domains from the lens of cognitive neuroscience, i.e., in terms of the brain areas mediating the role of such processes in the ability to make sense of others' behavior and plan socially appropriate actions. The increasing evidence on the “social brain” obtained from healthy young individuals nowadays constitutes the baseline for detecting changes in social cognitive skills associated with physiological aging or pathological conditions. In the latter case, impairments in one or more of the abovementioned domains represent a prominent concern, or even a core facet, of neurological (e.g., acquired brain injury or neurodegenerative diseases), psychiatric (e.g., schizophrenia), and developmental (e.g., autism) disorders. To pave the way for the other papers of this issue, addressing the social cognitive deficits associated with severe acquired brain injury, we will briefly discuss the available evidence on the status of social cognition in normal aging and its breakdown in neurodegenerative disorders. Although the assessment and treatment of such impairments is a relatively novel sector in neurorehabilitation, the evidence summarized here strongly suggests that the development of remediation procedures for social cognitive skills will represent a future field of translational research in clinical neuroscience.

Growing a social brain

It has long been assumed that social animals, such as humans, are born with a brain system that has evolved to support social affiliation. However, the evidence does not necessarily support this assumption. Alternatively, social animals can be defined as those who cannot survive alone and rely on members from their group to regulate their ongoing physiology (or allostasis). The rather simple evolutionary constraint of social dependency for survival can be sufficient to make the social environment vitally salient, and to provide the ultimate driving force for socially crafted brain development and learning. In this Perspective, we propose a framework for sociality and specify a set of hypotheses on the mechanisms of social development and underlying neural systems. The theoretical shift proposed here implies that profound human characteristics, including but not limited to sociality, are acquired at an early age, while social interactions provide key wiring instructions that determine brain development.

Working memory deficit in drug-resistant epilepsy with an amygdala lesion

This study compared temporal lobe epilepsy (TLE) patients with amygdala lesion (AL) without hippocampal sclerosis (HS) (TLE-AL) with patients with TLE and HS without AL (TLE-HS). Both subtypes of TLE arose from the right hemisphere.

The TLE-AL group exhibited a lower Working Memory Index (WMI) on the Wechsler Adult Intelligence Scale, third edition (WAIS-III), indicating that the amygdala in the right hemisphere is involved in memory-related function. [18F]fluorodeoxyglucose positron emission topography (FDG-PET) showed glucose hypometabolism limited to the right uncus for the TLE-AL group.

The results suggest the importance of considering cognitive functions in the non-dominant hemisphere to prevent impairment after surgery.

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Low working memory index (WMI) was found due to a right amygdala lesion (AL).

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Glucose hypometabolism was limited to the right uncus for the Temporal Lobe Epilepsy-AL (TLE-AL) patients

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Glucose hypometabolism was associated with low WMI in the TLE-AL patients

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We suggest the need to consider cognitive function in non-dominant hemisphere

RDoC-based categorization of amygdala functions and its implications in autism

Confusion endures as to the exact role of the amygdala in relation to autism. To help resolve this we turned to the NIMH's Research Domain Criteria (RDoC) which provides a classification schema that identifies different categories of behaviors that can turn pathologic in mental health disorders, e.g. autism. While RDoC incorporates all the known neurobiological substrates for each domain, this review will focus primarily on the amygdala. We first consider the amygdala from an anatomical, historical, and developmental perspective. Next, we examine the different domains and constructs of RDoC that the amygdala is involved in: Negative Valence Systems, Positive Valence Systems, Cognitive Systems, Social Processes, and Arousal and Regulatory Systems. Then the evidence for a dysfunctional amygdala in autism is presented with a focus on alterations in development, prenatal valproic acid exposure as a model for ASD, and changes in the oxytocin system therein. Finally, a synthesis of RDoC, the amygdala, and autism is offered, emphasizing the task of disambiguation and suggestions for future research.

Amygdala real-time functional magnetic resonance imaging neurofeedback for major depressive disorder: A review

Advances in imaging technologies have allowed for the analysis of functional magnetic resonance imaging data in real-time (rtfMRI), leading to the development of neurofeedback (nf) training. This rtfMRI-nf training utilizes functional magnetic resonance imaging (fMRI) tomographic localization capacity to allow a person to see and regulate the localized hemodynamic signal from his or her own brain. In this review, we summarize the results of several studies that have developed and applied neurofeedback training to healthy and depressed individuals with the amygdala as the neurofeedback target and the goal to increase the hemodynamic response during positive autobiographical memory recall. We review these studies and highlight some of the challenges and advances in developing an rtfMRI-nf paradigm for broader use in psychiatric populations. The work described focuses on our line of research aiming to develop the rtfMRI-nf into an intervention, and includes a discussion of the selection of a region of interest for feedback, selecting a control condition, behavioral and cognitive effects of training, and predicting which participants are most likely to respond well to training. While the results of these studies are encouraging and suggest the clinical potential of amygdala rtfMRI-nf in alleviating symptoms of major depressive disorder, larger studies are warranted to confirm its efficacy.

Involvement of the Amygdala in Memory and Psychosocial Functioning in Pediatric-Onset Multiple Sclerosis

Youth with multiple sclerosis (MS) often experience cognitive impairment and psychosocial disturbances. We describe the relationship between memory function, psychosocial skills, and brain volume in 32 patients with pediatric-onset MS and 30 controls. Amygdala volume was significantly lower in patients compared with controls. In general, poorer memory was associated with reduced functional communication skills and reduced amygdala volume. Greater amygdala volume in patients correlated with parent-reported functional communication and social skills. Adjusting for whole-brain volume, right amygdala volume was positively associated with visual memory; left amygdala volume was a stronger predictor of parent-reported social skills.

Longitudinal relationships among depressive symptoms, cortisol, and brain atrophy in the neocortex and the hippocampus

OBJECTIVE

Depression is associated with accelerated aging and age-related diseases. However, mechanisms underlying this relationship remain unclear. The aim of this study was to longitudinally assess the link between depressive symptoms, brain atrophy, and cortisol levels.

METHOD

Participants from the Betula prospective cohort study (mean age = 59 years, SD = 13.4 years) underwent clinical, neuropsychological and brain 3T MRI assessments at baseline and a 4-year follow-up. Cortisol levels were measured at baseline in four saliva samples. Cortical and hippocampal atrophy rates were estimated and compared between participants with and without depressive symptoms (n = 81) and correlated with cortisol levels (n = 49).

RESULTS

Atrophy in the left superior frontal gyrus and right lingual gyrus developed in parallel with depressive symptoms, and in the left temporal pole, superior temporal cortex, and supramarginal cortex after the onset of depressive symptom. Depression-related atrophy was significantly associated with elevated cortisol levels. Elevated cortisol levels were also associated with widespread prefrontal, parietal, lateral, and medial temporal atrophy.

CONCLUSION

Depressive symptoms and elevated cortisol levels are associated with atrophy of the prefrontal and limbic areas of the brain.

Design of optimal nonlinear network controllers for Alzheimer's disease

Brain stimulation can modulate the activity of neural circuits impaired by Alzheimer’s disease (AD), having promising clinical benefit. However, all individuals with the same condition currently receive identical brain stimulation, with limited theoretical basis for this generic approach. In this study, we introduce a control theory framework for obtaining exogenous signals that revert pathological electroencephalographic activity in AD at a minimal energetic cost, while reflecting patients’ biological variability. We used anatomical networks obtained from diffusion magnetic resonance images acquired by the Alzheimer’s Disease Neuroimaging Initiative (ADNI) as mediators for the interaction between Duffing oscillators. The nonlinear nature of the brain dynamics is preserved, given that we extend the so-called state-dependent Riccati equation control to reflect the stimulation objective in the high-dimensional neural system. By considering nonlinearities in our model, we identified regions for which control inputs fail to correct abnormal activity. There are changes to the way stimulated regions are ranked in terms of the energetic cost of controlling the entire network, from a linear to a nonlinear approach. We also found that limbic system and basal ganglia structures constitute the top target locations for stimulation in AD. Patients with highly integrated anatomical networks–namely, networks having low average shortest path length, high global efficiency–are the most suitable candidates for the propagation of stimuli and consequent success on the control task. Other diseases associated with alterations in brain dynamics and the self-control mechanisms of the brain can be addressed through our framework.

This work aims to close the knowledge gap between theory and experiment in brain stimulation. Previous modeling approaches for stimulation have overlooked the nonlinear dynamical nature of the brain and failed to shed light on efficient mechanisms for the exogenous control of the brain. Amid the current efforts for developing personalized medicine, we introduce a framework for producing tailored stimulation signals, based on individual neuroimaging data and innovative modeling. This is the first time, to our knowledge, that brain stimulation for the most common cause of dementia, Alzheimer’s disease, is theoretically addressed. Our approach leads to the identification of potential target regions and subjects to successfully respond to brain stimulation therapies and yields various disease-reverting signals. Although focused on Alzheimer’s in this study, our methodology could be applied to other clinical conditions characterized by abnormalities in brain dynamics, like epilepsy and Parkinson’s, the treatment of which can benefit from the use of optimal control strategies.

High early life stress and aberrant amygdala activity: risk factors for elevated neuropsychiatric symptoms in HIV+ adults

Relative to HIV-negative adults, HIV+ adults report elevated levels of early life stress (ELS). In non-HIV samples, high ELS has been linked to abnormalities in brain structure and function, as well as increased risk of neuropsychiatric symptoms. Yet, little is known about the neural effects of high ELS, and their relation to elevated neuropsychiatric symptoms, in HIV+ adults. Recent studies have revealed combined effects of HIV and high ELS on amygdala morphometry. Aberrant amygdala activity is prominently implicated in studies of neuropsychiatric symptomology in non-HIV samples. Hence, this preliminary study examined: 1) the combined effects of HIV and high ELS on amygdala activity, and 2) the relation between amygdala activity and neuropsychiatric symptoms in HIV+ adults. We included 28 HIV+ adults and 25 demographically-matched HIV-negative control (HC) adults. ELS exposure was quantified using a retrospective ELS questionnaire, which defined four groups: HIV+ Low-ELS (N = 15); HIV+ High-ELS (N = 13); HC Low-ELS (N = 16); and HC High-ELS (N = 9). Participants completed a battery of neuropsychiatric measures. BOLD fMRI assessed amygdala reactivity during explicit observation of fearful/angry faces. High-ELS participants demonstrated reduced levels of amygdala reactivity relative to Low-ELS participants. HIV+ High-ELS participants reported higher levels of neuropsychiatric symptoms than all other groups. In the HIV+ group, lower amygdala responses were associated with higher neuropsychiatric symptoms, particularly depression, anxiety, and alexithymia. Collectively, these results suggest that high ELS exposure is a significant risk factor for neuropsychiatric symptoms in HIV+ adults. Furthermore, our results implicate ELS-related abnormalities in amygdala activity in the etiology of neuropsychiatric symptoms in HIV+ adults.

Neural Reorganization Due to Neonatal Amygdala Lesions in the Rhesus Monkey: Changes in Morphology and Network Structure

It is generally believed that neural damage that occurs early in development is associated with greater adaptive capacity relative to similar damage in an older individual. However, few studies have surveyed whole brain changes following early focal damage. In this report, we employed multimodal magnetic resonance imaging analyses of adult rhesus macaque monkeys who had previously undergone bilateral, neurotoxic lesions of the amygdala at about 2 weeks of age. A deformation-based morphometric approach demonstrated reduction of the volumes of the anterior temporal lobe, anterior commissure, basal ganglia, and pulvinar in animals with early amygdala lesions compared to controls. In contrast, animals with early amygdala lesions had an enlarged cingulate cortex, medial superior frontal gyrus, and medial parietal cortex. Diffusion-weighted imaging tractography and network analysis were also used to compare connectivity patterns and higher-level measures of communication across the brain. Using the communicability metric, which integrates direct and indirect paths between regions, lesioned animals showed extensive degradation of network integrity in the temporal and orbitofrontal cortices. This work demonstrates both degenerative as well as progressive large-scale neural changes following long-term recovery from neonatal focal brain damage.

Amygdalar Gray Matter Volume and Social Relating in Schizophrenia

BACKGROUND

Poor social relating is a prominent feature of schizophrenia. The amygdala has been suggested as an important node in social brain networks.

METHODS

By using structural magnetic resonance imaging, this study examined, for the first time, the relationship between amygdalar gray matter (GM) volume and social relating in 35 schizophrenia patients. Social anhedonia, interaction anxiety, extraversion, and sociable tendencies were assessed as indices of social relating.

RESULTS

A correlation between GM volume in the amygdala and enhanced social relating was revealed.

CONCLUSION

These findings indicate that volumetric decreases in the amygdala are related to impoverished sociability in schizophrenia.

Tourette syndrome: a disorder of the social decision-making network

Tourette syndrome is a common neurodevelopmental disorder defined by characteristic involuntary movements, tics, with both motor and phonic components. Tourette syndrome is usually conceptualized as a basal ganglia disorder, with an emphasis on striatal dysfunction. While considerable evidence is consistent with these concepts, imaging data suggest diffuse functional and structural abnormalities in Tourette syndrome brain. Tourette syndrome exhibits features that are difficult to explain solely based on basal ganglia circuit dysfunctions. These features include the natural history of tic expression, with typical onset of tics around ages 5 to 7 years and exacerbation during the peri-pubertal years, marked sex disparity with higher male prevalence, and the characteristic distribution of tics. The latter are usually repetitive, somewhat stereotyped involuntary eye, facial and head movements, and phonations. A major functional role of eye, face, and head movements is social signalling. Prior work in social neuroscience identified a phylogenetically conserved network of sexually dimorphic subcortical nuclei, the Social Behaviour Network, mediating many social behaviours. Social behaviour network function is modulated developmentally by gonadal steroids and social behaviour network outputs are stereotyped sex and species specific behaviours. In 2011 O'Connell and Hofmann proposed that the social behaviour network interdigitates with the basal ganglia to form a greater network, the social decision-making network. The social decision-making network may have two functionally complementary limbs: the basal ganglia component responsible for evaluation of socially relevant stimuli and actions with the social behaviour network component responsible for the performance of social acts. Social decision-making network dysfunction can explain major features of the neurobiology of Tourette syndrome. Tourette syndrome may be a disorder of social communication resulting from developmental abnormalities at several levels of the social decision-making network. The social decision-making network dysfunction hypothesis suggests new avenues for research in Tourette syndrome and new potential therapeutic targets.

Taking two to tango: fMRI analysis of improvised joint action with physical contact

Many forms of joint action involve physical coupling between the participants, such as when moving a sofa together or dancing a tango. We report the results of a novel two-person functional MRI study in which trained couple dancers engaged in bimanual contact with an experimenter standing next to the bore of the magnet, and in which the two alternated between being the leader and the follower of joint improvised movements. Leading showed a general pattern of self-orientation, being associated with brain areas involved in motor planning, navigation, sequencing, action monitoring, and error correction. In contrast, following showed a far more sensory, externally-oriented pattern, revealing areas involved in somatosensation, proprioception, motion tracking, social cognition, and outcome monitoring. We also had participants perform a "mutual" condition in which the movement patterns were pre-learned and the roles were symmetric, thereby minimizing any tendency toward either leading or following. The mutual condition showed greater activity in brain areas involved in mentalizing and social reward than did leading or following. Finally, the analysis of improvisation revealed the dual importance of motor-planning and working-memory areas. We discuss these results in terms of theories of both joint action and improvisation.

The Amygdala as a Locus of Pathologic Misfolding in Neurodegenerative Diseases

Over the course of most common neurodegenerative diseases the amygdala accumulates pathologically misfolded proteins. Misfolding of 1 protein in aged brains often is accompanied by the misfolding of other proteins, suggesting synergistic mechanisms. The multiplicity of pathogenic processes in human amygdalae has potentially important implications for the pathogenesis of Alzheimer disease, Lewy body diseases, chronic traumatic encephalopathy, primary age-related tauopathy, and hippocampal sclerosis, and for the biomarkers used to diagnose those diseases. Converging data indicate that the amygdala may represent a preferential locus for a pivotal transition from a relatively benign clinical condition to a more aggressive disease wherein multiple protein species are misfolded. Thus, understanding of amygdalar pathobiology may yield insights relevant to diagnoses and therapies; it is, however, a complex and imperfectly defined brain region. Here, we review aspects of amygdalar anatomy, connectivity, vasculature, and pathologic involvement in neurodegenerative diseases with supporting data from the University of Kentucky Alzheimer's Disease Center autopsy cohort. Immunohistochemical staining of amygdalae for Aβ, Tau, α-synuclein, and TDP-43 highlight the often-coexisting pathologies. We suggest that the amygdala may represent an "incubator" for misfolded proteins and that it is possible that misfolded amygdalar protein species are yet to be discovered.