[Purpose] Thinking is a fundamental human brain function. Motor behavior often accompanies thinking, but the role of thinking in mediating motor activity has not been well explored, especially so when a man is going to initiate or suppress actions at behavioral changes. To investigate the brain activities at the time of a behavioral shift induced voluntarily and passively, we conducted a finger-tapping task using the functional magnetic resonance imaging (fMRI). Here, we report some results of the pilot study. [Methods] Five healthy volunteers underwent 3T MRI scans (Philips, Ingenia). A short block design was employed with four conditions: voluntarily and passively cued initiation and suppression of finger tapping. Each condition was presented 6 times randomly in a session. All subjects performed three sessions. In each block, a white dot was basically presented for eyes fixation, and just after 'Self' or 'Cue' word presentation, a few hundred milliseconds lasting green and red cross were shortly presented as signals for initiating and stopping the tapping, respectively. In the 'Self' condition, subjects were instructed to change behaviors at their will within a block. In the 'Cue' condition, they were forced to follow the rule of green and red crosses. The fMRI data by event-related acquisition were analyzed using a fixed effect model by SPM8. [Results] The middle frontal cortex (MFC) and supplementary motor area (SMA) were activated in the voluntary conditions compared to the passively cued conditions. The inferior parietal lobe (IPL) was commonly activated at behavioral changes except for the passive condition of stopping movement. [Discussion] The current results indicated that brain activations during thinking and motor execution are inseparable. The MFC and SMA may subserve active thinking for behavior selection. The IPL activation is implicated when the selected behavior (tapping) should be maintained during thinking as it is.