Altered Coupling of Psychological Relaxation and Regional Volume of Brain Reward Areas in Multiple Sclerosis.

Psychological stress can influence the severity of multiple sclerosis (MS), but little is known about neurobiological factors potentially counteracting these effects. To identify gray matter (GM) brain regions related to relaxation after stress exposure in persons with MS (PwMS). 36 PwMS and 21 healthy controls (HCs) reported their feeling of relaxation during a mild stress task. These markers were related to regional GM volumes, heart rate, and depressive symptoms. Relaxation was differentially linked to heart rate in both groups ( = 2.20, = 0.017), i.e., both markers were only related in HCs. Relaxation was positively linked to depressive symptoms across all participants ( = 1.99, = 0.045) although this link differed weakly between groups ( = 1.62, = 0.108). Primarily, the volume in medial temporal gyrus was negatively linked to relaxation in PwMS ( = -5.55, p = 0.018). A group-specific coupling of relaxation and GM volume was found in ventromedial prefrontal cortex (VMPFC) ( = -4.89, p = 0.039). PwMS appear unable to integrate peripheral stress signals into their perception of relaxation. Together with the group-specific coupling of relaxation and VMPFC volume, a key area of the brain reward system for valuation of affectively relevant stimuli, this finding suggests a clinically relevant misinterpretation of stress-related affective stimuli in MS.