The Connectivity–Based Parcellation of The Angular Gyrus: Fiber Dissection And MR Tractography Study

The angular gyrus (AG) wraps the posterior end of the superior temporal sulcus (STS), so it is considered as a continuation of the superior/middle temporal gyrus and forms the inferior parietal lobule (IPL) with the supramarginal gyrus (SMG). The AG was functionally divided in the literature, but there is no fiber dissection study in this context. This study divided AG into superior (sAG) and inferior (iAG) parts by focusing on STS. Red blue silicone injected eight human cadaveric cerebrums were dissected via the Klingler method focusing on the AG. White matter (WM) tracts identified during dissection were then reconstructed on the Human Connectome Project 1065 individual template for validation. According to this study, superior longitudinal fasciculus (SLF) II and middle longitudinal fasciculus (MdLF) are associated with sAG; the anterior commissure (AC), optic radiation (OR) with iAG; the arcuate fasciculus (AF), inferior frontooccipital fasciculus (IFOF), and tapetum (Tp) with both parts. In cortical parcellation of AG based on STS, sAG and iAG were found to be associated with different fiber tracts. Although it has been shown in previous studies that there are functionally different subunits with AG parcellation, here, for the first time, different functions of the subunits have been revealed with cadaveric dissection and tractography images.

Examining the Neural Correlates of Error Awareness in a Large fMRI Study

Goal-directed behaviour is dependent upon the ability to detect errors and implement appropriate post-error adjustments. Accordingly, several studies have explored the neural activity underlying error-monitoring processes, identifying the insula cortex as crucial for error awareness and reporting mixed findings with respect to the anterior cingulate cortex. Variable patterns of activation have previously been attributed to insufficient statistical power. We therefore sought to clarify the neural correlates of error awareness in a large event-related functional magnetic resonance imaging (MRI) study. Four hundred and two healthy participants undertook the Error Awareness Task, a motor Go/No-Go response inhibition paradigm in which participants were required to indicate their awareness of commission errors. Compared to unaware errors, aware errors were accompanied by significantly greater activity in a network of regions including the insula cortex, supramarginal gyrus, and midline structures such as the anterior cingulate cortex and supplementary motor area. Error awareness activity was related to indices of task performance and dimensional measures of psychopathology in select regions including the insula, supramarginal gyrus and supplementary motor area. Taken together, we identified a robust and reliable neural network associated with error awareness.

Caregiver Stress and Empathy: Neural and Hormonal Correlates

Providing care to older adults with chronic conditions can be emotionally meaningful and stressful. The tend-and-befriend theory highlights the role of affiliation/empathy in stress reduction, but it has not been established whether this theory extends to caregivers for older adults. Addressing this gap, we assessed caregiver empathy and stress through behavioral, hormone, and neuroimaging measures. In Experiment 1, we compared 19 caregivers (Mage=67.1) to 24 non-caregivers (Mage=72.6), and found that caregivers with a greater reduction in cortisol to an empathic context showed greater prosocial behavior (r2=0.3). In experiment 2 (N=32), we examined differences between caregivers and non-caregivers in whole brain resting-state functional connectivity (RSFC) with seed regions of interest (posterior cingulate cortex (PCC); amygdala), and covariation of RSFC with empathy (α=0.05). For emotional empathy, caregivers had stronger connectivity between the PCC seed, medial prefrontal cortex, and right supramarginal gyrus, and between the amygdala seed and the right middle frontal gyrus.

Tryptophan-enriched diet or 5-hydroxytryptophan supplementation given in a randomized controlled trial impacts social cognition on a neural and behavioral level

Understanding of emotions and intentions are key processes in social cognition at which serotonin is an important neuromodulator. Its precursor is the essential amino acid tryptophan (TRP). Reduced TRP availability leads to weaker impulse control ability and higher aggression, while TRP supplementation promotes confidence. In a double-blind placebo-controlled fMRI study with 77 healthy adults, we investigated the influence of a 4 week TRP enriched diet and an acute 5-hydroxytryptophan (5-HTP) intake on two social-cognitive tasks, a moral evaluation and an emotion recognition task. With 5-HTP, immoral behavior without negative consequences was rated as more reprehensible. Additionally, during story reading, activation in insula and supramarginal gyrus was increased after TRP intake. No significant effects of TRP on emotion recognition were identified for the whole sample. Importantly, emotion recognition ability decreased with age which was for positive emotions compensated by TRP. Since the supramarginal gyrus is associated with empathy, pain and related information integration results could be interpreted as reflecting stricter evaluation of negative behavior due to better integration of information. Improved recognition of positive emotions with TRP in older participants supports the use of a TRP-rich diet to compensate for age related decline in social-cognitive processes.

Individual Symptom Severity in Adult Autism Spectrum Disorder Predicts Reduction in Right Dorsal Stream Neural Activity During Live Eye-to-Eye Contact

Background: Social symptomatology quantified by clinical interview (Autism Diagnostic Observation Schedule, ADOS) and self-report (Social Responsiveness Scale, SRS) indicate symptom severity in autism spectrum disorder (ASD). Reluctance to engage in interpersonal eye contact is a frequently observed behavioral hallmark, though neural bases for these difficulties and relation to symptomatology are not understood. We test the hypothesis that eye contact in ASD activates atypical neural mechanisms that are related to individual differences in symptomatology. Methods: Neural activity represented by hemodynamic signals was acquired by functional near-infrared spectroscopy (fNIRS) during real person-to-person eye contact (confirmed by eye-tracking) for 17 adult ASD (3 female, 14 male) and 19 typically-developed (TD) participants (8 female, 11 male). Assessment of social function was based on ADOS scores for ASD participants and SRS scores for the combined group of ASD and TD participants. Results: Individual ADOS scores were negatively correlated (r = -0.69) with individual fNIRS beta-values (representing strength of hemodynamic signals) within clusters in the right dorsal stream regions: somatosensory cortices, angular gyrus, and supramarginal gyrus. Hemodynamic responses in the right dorsolateral prefrontal cortex (DLPFC) were also negatively correlated (r = -0.77) with ADOS scores. Similarly, SRS scores for the combined ASD and TD groups were also negatively correlated (r = -0.58) with somatosensory cortices and the supramarginal gyrus. Conclusions: These findings are consistent with the hypothesis that neural mechanisms in the dorsal stream and DLPFC are related to social symptomatology and implicate high-level interactive face and eye-processing systems as potential neurobiological markers of ASD.

Effective connectivity reveals distinctive patterns in response to others' genuine affective experience of disgust as compared to pain

Empathy is significantly influenced by the identification of others' emotions. In a recent study, we have found increased activation in the anterior insular cortex (aIns) that could be attributed to affect sharing rather than perceptual saliency, when seeing another person genuinely experiencing pain as opposed to merely acting to be in pain. This study further revealed effective connectivity between aIns and the right supramarginal gyrus (rSMG) to track what another person really feels. In the present study, we used a similar paradigm to investigate the corresponding neural signatures in the domain of empathy for disgust - with participants seeing others genuinely sniffing unpleasant odors as compared to pretending to smell something disgusting. Consistent with the previous findings on pain, we found stronger activations in aIns associated with affect sharing for genuine disgust compared with pretended disgust. However, instead of rSMG we found engagement of the olfactory cortex. Using dynamic causal modeling (DCM), we estimated the neural dynamics of aIns and the olfactory cortex between the genuine and pretended conditions. This revealed an increased excitatory modulatory effect for genuine disgust compared to pretended disgust. For genuine disgust only, brain-to-behavior regression analyses highlighted a link between the observed modulatory effect and the perspective-taking empathic trait. Altogether, the current findings complement and expand our previous work, by showing that perceptual saliency alone does not explain responses in the insular cortex. Moreover, it reveals that different brain networks are implicated in a modality-specific way when sharing the affective experiences associated with pain vs. disgust.

Meta-analytic connectivity modelling of deception-related brain regions

Brain-based deception research began only two decades ago and has since included a wide variety of contexts and response modalities for deception paradigms. Investigations of this sort serve to better our neuroscientific and legal knowledge of the ways in which individuals deceive others. To this end, we conducted activation likelihood estimation (ALE) and meta-analytic connectivity modelling (MACM) using BrainMap software to examine 45 task-based fMRI brain activation studies on deception. An activation likelihood estimation comparing activations during deceptive versus honest behavior revealed 7 significant peak activation clusters (bilateral insula, left superior frontal gyrus, bilateral supramarginal gyrus, and bilateral medial frontal gyrus). Meta-analytic connectivity modelling revealed an interconnected network amongst the 7 regions comprising both unidirectional and bidirectional connections. Together with subsequent behavioral and paradigm decoding, these findings implicate the supramarginal gyrus as a key component for the sociocognitive process of deception.

Neural dynamics between anterior insular cortex and right supramarginal gyrus dissociate genuine affect sharing from perceptual saliency of pretended pain

Empathy for pain engages both shared affective responses and self-other distinction. In this study, we addressed the highly debated question of whether neural responses previously linked to affect sharing could result from the perception of salient affective displays. Moreover, we investigated how the brain network involved in affect sharing and self-other distinction underpinned our response to a pain that is either perceived as genuine or pretended (while in fact both were acted for reasons of experimental control). We found stronger activations in regions associated with affect sharing (anterior insula [aIns] and anterior mid-cingulate cortex) as well as with affective self-other distinction (right supramarginal gyrus [rSMG]), in participants watching video clips of genuine vs. pretended facial expressions of pain. Using dynamic causal modeling, we then assessed the neural dynamics between the right aIns and rSMG in these two conditions. This revealed a reduced inhibitory effect on the aIns to rSMG connection for genuine pain compared to pretended pain. For genuine pain only, brain-to-behavior regression analyses highlighted a linkage between this inhibitory effect on the one hand, and pain ratings as well as empathic traits on the other. These findings imply that if the pain of others is genuine and thus calls for an appropriate empathic response, neural responses in the aIns indeed seem related to affect sharing and self-other distinction is engaged to avoid empathic over-arousal. In contrast, if others merely pretend to be in pain, the perceptual salience of their painful expression results in neural responses that are down-regulated to avoid inappropriate affect sharing and social support.

Sleep disturbances are associated with cortical and subcortical atrophy in alcohol use disorder

Sleep disturbances are prominent in patients with alcohol use disorder (AUD) and predict relapse. So far, the mechanisms underlying sleep disruptions in AUD are poorly understood. Because sleep-related regions vastly overlap with regions, where patients with AUD showed pronounced grey matter (GM) reduction; we hypothesized that GM structure could contribute to sleep disturbances associated with chronic alcohol use. We combined sleep EEG recording and high-resolution structural brain imaging to examine the GM-sleep associations in 36 AUD vs. 26 healthy controls (HC). The patterns of GM-sleep associations differed for N3 vs. REM sleep and for AUD vs. HC. For cortical thickness (CT), CT-sleep associations were significant in AUD but not in HC and were lateralized such that lower CT in right hemisphere was associated with shorter N3, whereas in left hemisphere was associated with shorter REM sleep. For the GM density (GMD), we observed a more extensive positive GMD-N3 association in AUD (right orbitofrontal cortex, cerebellum, dorsal cingulate and occipital cortex) than in HC (right orbitofrontal cortex), and the GMD-REM association was positive in AUD (midline, motor and paralimbic regions) whereas negative in HC (the left supramarginal gyrus). GM structure mediated the effect of chronic alcohol use on the duration of N3 and the age by alcohol effect on REM sleep. Our findings provide evidence that sleep disturbances in AUD were associated with GM reductions. Targeting sleep-related regions might improve sleep in AUD and enhance sleep-induced benefits in cognition and emotional regulation for recovery.