Different distribution of the activated areas in the dorsal premotor cortex during visual and auditory reaction-time tasks

Sensorimotor association is an essential aspect of behavior. The dorsal par t of the premotor cortex (PMd) is known to have an important role in sensor imotor association. Although it is suggested that the partially segregated groups of neurons are involved in sensorimotor association in different sen sory modalities, it is not yet clear whether these groups occupy the PMd to the same or different extent. Therefore, we performed a functional magneti c resonance imaging study to compare activated regions in the PMd during si mple reaction-time tasks with visual and auditory cues. Eight normal volunt eers performed two simple reaction time tasks with a conventional on-off de sign; one is with a visual cue and the other is with an auditory cue. In bo th tasks, two regions in the left primary motor area (M1) (4a and 4p) and t he bilateral PMd were activated. The two activated regions in the left M1 o ccupied the same areas in both the visual and the auditory tasks. However, in the PMd, the activated regions were situate medially during the visual t ask and laterally during the auditory task, along the precentral sulci. The re was no overlap of significantly activated regions between two tasks, and areas specifically activated during the visual task were observed in the m iddle of the precentral sulci, bilaterally. The results suggest that the di stribution of PMd subregions involved in sensorimotor association differ wh en the sensory cues are in different modalities. (C) 2001 Academic Press.