Motor response suppression and the prepotent tendency to respond: a parametric fMRI study

In the present study we utilised functional magnetic resonance imaging (fMR I) to examine cerebral activation during performance of a classic motor tas k in which response suppression load was parametrically varied. Linear incr eases in activity were observed in a distributed network of regions across both cerebral hemispheres, although with more extensive involvement of the right prefrontal cortex. Activated regions included prefrontal, parietal an d occipitotemporal cortices. Decreasing activation was similarly observed i n a distributed network of regions, These response forms are discussed in t erms of an increasing requirement for visual cue discrimination and suppres sion/selection of motor responses, and a decreasing probability of the occu rrence of non-target stimuli and attenuation of a prepotent tendency to res pond. The results support recent proposals for a dominant role for the righ t-hemisphere in performance of motor response suppression tasks that emphas ise the importance of the right prefrontal cortex. (C) 2000 Elsevier Scienc e Ltd. All rights reserved.