Sex- and age-related characteristics of brain functioning during task switching (fMRI study)

Abstract

This study is focused on changes in the brain function throughout the adulthood in healthy men and women performing task switching (TS) in the visual modality. One hundred and forty healthy subjects aged 20 to 65 years (69 men) participated in the experiments. In the fMRI study, the subjects performed a test that required switching attention between two objectives (classifying figures according to their form or number). Using the voxel-based morphometry (VBM), we calculated the volumes of gray and white matter in the whole brain and in selected areas. The results showed that a common feature of different age and sex groups performing the TS was bilateral activation of the dorsolateral prefrontal areas, the inferior parietal lobes and the inferior occipital gyrus. We also found a transition from local to diffuse activation occurring with age. In young men (20 to 30 years of age) compared to women, a greater increase in the BOLD signal was found in the prefrontal areas bilaterally, the right parietal lobe and insula, and, in addition, bilateral activation in the supplementary motor area which were not observed in women. Older men and women (51 to 65 years) had no significant differences. The study of the BOLD signal correlations with age in women at the age from 20 to 40 and men from 20 to 55 years showed no significant changes. With further increase of age in both groups we found a consequent increase in the number of brain areas which are activated. The VBM analysis showed a significant decrease in the volume of gray, but not white, matter with age. No significant correlations between age-related changes in the gray matter volume (both in the whole brain and in the specific areas) and BOLD signal in this age group were detected.