NeuroImage
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The present study investigated the premise that individual differences in autonomic physiology could be used to specify the nature and consequences of information processing taking place in medial prefrontal regions during cognitive reappraisal of unpleasant pictures. Neural (blood oxygenation level-dependent functional magnetic resonance imaging) and autonomic (electrodermal [EDA], pupil diameter, cardiac acceleration) signals were recorded simultaneously as twenty-six older people (ages 64-66 years) used reappraisal to increase, maintain, or decrease their responses to unpleasant pictures. EDA was higher when increasing and lower when decreasing compared to maintaining. ⋯ These data indicate that these two medial prefrontal regions are involved in the allocation of cognitive resources to regulate unpleasant emotion, and that they modulate emotional arousal in accordance with the regulatory goal. The emotional arousal effects were mediated by the right amygdala. Reappraisal-related activation in a third medial prefrontal region (subgenual anterior cingulate cortex) was not associated with similar patterns of change in any of the autonomic measures, thus highlighting regional specificity in the degree to which cognitive demand is reflected in medial prefrontal activation during reappraisal.
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Identifying brain systems that regulate or modulate autonomic nervous system functions may identify pathways through which psychosocial factors can influence health and disease. Reduced high-frequency heart rate variability (HF-HRV) characterizes anxiety disordered patients and is predictive of adverse myocardial events. Sex differences in the prevalence of anxiety disorders and cardiac diseases implicate the possibility of sex specific neural regulation of HF-HRV. ⋯ These findings underscore the importance of the emotional division of the anterior cingulate cortex, the prefrontal cortex and the striatum in cardiovagal activity. The study replicates and extends results from published functional neuroimaging studies on cardioregulatory or modulatory areas in healthy subjects to men and women with social phobia. Moreover, caudate functions, possibly related to dopaminergic neurotransmission, have sexually dimorphic effects on vagal modulation of the heart.
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Patients with irritable bowel syndrome (IBS) show decreased discomfort and pain thresholds to visceral stimuli, as well hypervigilance to gastrointestinal sensations, symptoms, and the context in which these visceral sensations and symptoms occur. Previous research demonstrated normalization of visceral hypersensitivity following repeated exposure to experimental rectal stimuli over a 12-month period that was associated with reduction in cortical regions functionally associated with attention and arousal. Building upon these functional analyses, multivariate functional and effective connectivity analyses were applied to [(15)O] water positron emission tomography (PET) data from 12 IBS patients (male=4) participating in a PET study before and after 4 visceral sensory testing sessions involving rectal balloon distensions over a 1-year period. ⋯ Next, path analysis within a structural equation modeling framework tested the hypothesis that perceptual habituation to the repeated visceral stimuli resulted in part from the reduced connectivity within a selective attention to threat network over time. Two independent, perception-related networks comprised of interoceptive, attentional and arousal regions were engaged differentially during expectation and distension. In addition, changes in the effective connectivity of an attentional network as well as modulatory amygdala influence suggested that perceptual habituation associated with repeated stimulus delivery results both in an increase in top-down modulation of attentional circuits, as well as in a reduction of amygdala-related interference with attentional mechanisms.
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Magnetic resonance parameters, such as longitudinal (T1) and transverse (T2) relaxation times and proton density (PD) provide intrinsic information about the human brain. In vivo quantification of these parameters may enable detection of subtle regional grey matter (GM) or white matter (WM) differences and permit neurological disease detection and monitoring. The aims of the study were to quantify T1, T2 and PD values in all cortical gray matter regions for a group of healthy volunteers scanned at 1.5 T and to cluster regions showing statistically distinguishable tissue characteristics. ⋯ Correspondence analysis (CA) and hierarchical clustering (HC) were combined and applied to averaged T1, T2 and PD values within each VOI in order to identify groups of anatomical structures that are related statistically. Interestingly, except for one structure, all VOIs were grouped with left-right symmetry and showed an interesting pattern: the four lobes (frontal, occipital, parietal and temporal) were roughly clustered and the precentral and postcentral gyri were merged together. Our study shows that CA and HC analysis of MRI relaxation parameters and proton density can be used for cortical clustering of atlas-defined cortical regions.
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Wallerian degeneration of the corticospinal tract (CST) after motor pathway ischemic stroke can be characterized by diffusion tensor imaging (DTI). However, the dynamic evolution of the diffusion indices in the degenerated CST has not previously been completely identified. We investigated this dynamic evolution and the relationship between early changes of the diffusion indices in the degenerated CST and long-term clinical outcomes. ⋯ The rlambda(23) increased during the first 3 months and then stabilized. We also found that the changes in the rFA between the first 2 time points were correlated with the NIHSS (P=0.00003) and the Motricity Indices (P=0.0004) after 1 year. Our results suggest that for patients with motor pathway stroke the diffusion indices in the degenerated CST stabilize within 3 months and that early changes in the rFA of the CST may predict long-term clinical outcomes.