Multifractal and entropy analysis of resting-state electroencephalography reveals spatial organization in local dynamic functional connectivity

Functional connectivity of the brain fluctuates even in resting-state condition. It has been reported recently that fluctuations of global functional network topology and those of individual connections between brain regions expressed multifractal scaling. To expand on these findings, in this study we investigated if multifractality was indeed an inherent property of dynamic functional connectivity (DFC) on the regional level as well. Furthermore, we explored if local DFC showed region-specific differences in its multifractal and entropy-related features. DFC analyses were performed on 62-channel, resting-state electroencephalography recordings of twelve young, healthy subjects. Surrogate data testing verified the true multifractal nature of regional DFC that could be attributed to the presumed nonlinear nature of the underlying processes. Moreover, we found a characteristic spatial distribution of local connectivity dynamics, in that frontal and occipital regions showed stronger long-range correlation and higher degree of multifractality, whereas the highest values of entropy were found over the central and temporal regions. The revealed topology reflected well the underlying resting-state network organization of the brain. The presented results and the proposed analysis framework could improve our understanding on how resting-state brain activity is spatio-temporally organized and may provide potential biomarkers for future clinical research

Altered structural brain asymmetry in autism spectrum disorder in a study of 54 datasets

Altered structural brain asymmetry in autism spectrum disorder (ASD) has been reported. However, findings have been inconsistent, likely due to limited sample sizes. Here we investigated 1,774 individuals with ASD and 1,809 controls, from 54 independent data sets of the ENIGMA consortium. ASD was significantly associated with alterations of cortical thickness asymmetry in mostly medial frontal, orbitofrontal, cingulate and inferior temporal areas, and also with asymmetry of orbitofrontal surface area. These differences generally involved reduced asymmetry in individuals with ASD compared to controls. Furthermore, putamen volume asymmetry was significantly increased in ASD. The largest case-control effect size was Cohen’s d = −0.13, for asymmetry of superior frontal cortical thickness. Most effects did not depend on age, sex, IQ, severity or medication use. Altered lateralized neurodevelopment may therefore be a feature of ASD, affecting widespread brain regions with diverse functions. Large-scale analysis was necessary to quantify subtle alterations of brain structural asymmetry in ASD

Fear of the Unknown: Uncertain Anticipation Reveals Amygdala Alterations in Childhood Anxiety Disorders

Children with anxiety disorders (ADs) experience persistent fear and worries that are highly debilitating, conferring risk for lifelong psychopathology. Anticipatory anxiety is a core clinical feature of childhood ADs, often leading to avoidance of uncertain and novel situations. Extensive studies in non-human animals implicate amygdala dysfunction as a critical substrate for early life anxiety. To test specific amygdala-focused hypotheses in preadolescent children with ADs, we used fMRI to characterize amygdala activation during uncertain anticipation and in response to unexpected stimuli. Forty preadolescent (age 8–12 years) children, 20 unmedicated AD patients and 20 matched controls completed an anticipation task during an fMRI scan. In the task, symbolic cues preceded fear or neutral faces, such that ‘certain ’ cues always predicted the presentation of fear or neutral faces, whereas ‘uncertain ’ cues were equally likely to be followed by fear or neutral faces. Both AD children and controls showed robust amygdala response to faces. In response to the uncertain cues, AD children had increased amygdala activation relative to controls. Moreover, in the AD children, faces preceded by an ‘uncertain’ cue elicited increased amygdala activation, as compared with the same faces following a ‘certain ’ cue. Children with ADs experience distress both in anticipation of and during novel and surprising events. Our findings suggest that increased amygdala activation may hav