Activity related to visual search. (A) Statistical parametric maps activated by visual search (random-effect analysis of 13 subjects, P < 0.05, corrected). In order to identify brain regions activated by visual search, we calculated percent signal change evoked during present and absent trials as compared with that for null trial. Anatomical locations were mapped on axial template brains. Top: Sections passing through visual cortices (left), intraparietal sulcus (middle), and precentral gyrus (right) in the pre-fatigue session. Bottom: Sections passing through right visual cortex (left) and left visual cortex (right) in the post-fatigue session. Crossing line indicates the local activity maximum of each brain region. The right (R) and left (L) sides are indicated. (B) Activity in the visual cortices during the visual search in the pre- (Pre) and post-fatigue (Post) sessions of the normal and CFS patient groups. Magnitude of the activity was calculated as the peak signal change (%) averaged across the activated areas. (C) Activity change rate in the visual cortices during the visual search of the normal and CFS patient groups. Activity change rate (%/h) was calculated as change of activity in the visual cortices during the visual search from pre-fatigue to post-fatigue sessions divided by the session time (hour) of the fatigue-inducing period × 100. Data are mean and SEM. ns, no significant difference (unpaired t-test). Closed columns, normal subjects; open columns, CFS subjects.