Experimental procedure. Experiment included 3 sessions: Pre-fatigue, fatigue, and post-fatigue sessions. Subjects performed pre-fatigue, fatigue, and post-fatigue sessions lying on the MRI scanner table with both ears plugged. The time interval between 2 successive sessions was 1 min. For the fatigue session (fatigue-inducing period), normal subjects performed visual search trials (present or absent trials) for 1 hour, while CFS patients performed visual search trials for 30 min. During this period, continual visual search trials were performed; null trials were not included. In the pre- or post-fatigue sessions, subjects performed visual search or null trials for 6 min.