Whole Blood Serotonin Levels in Healthy Elderly are Negatively Associated with the Functional Activity of Emotion-related Brain Regions
Understanding the role of neuromodulators of socio-affective processing is important to ensure psychological wellbeing during older years. To assess the potential implication of serotonin levels in socio-affective processing in older adults, this study investigated the link between peripheral measures of serotonin (i.e., whole blood) and brain and behavioral responses to emotional information in healthy elderly (N =119). A priori regions of interest (ROI) were selected due to both their role in emotion processing and their dense serotonergic innervation (i.e., amygdalae, insulae, dorsal anterior cingulate cortex and subgenual cingulate gyrus). Brain responses to emotional information were computed as the ROI-specific difference between in functional brain activity to high vs. low emotional videos. The same procedure was carried out for the subsequent resting periods. Zero-order and partial correlation analyses were performed between these ROI-specific increases in brain activations and whole blood serotonin levels. Significant negative associations were observed between serotonin and functional activity for the bilateral insula, dorsal anterior cingulate cortex and subgenual gyrus. The results were replicated by confirmatory voxel-wise analyses, highlighting the specificity of the findings. These effects were only present during the videos, but not in the resting periods. There were no associations between 5-HT levels and behavioral measures of socio-affective functions. Our results mirror pharmacological and genetic studies showing that changes in the serotonergic system may lead to enhanced emotional brain responses. Given the involvement of serotonin in a wide range of age-related changes, our study sets the basis for future research aiming to characterize the role of this endogenous modulator in emotion processing of elderly populations.
Steps to reproduce
- Download all the files in the same order. - R scripts show the paths and instruction to reproduce the analyses