Dissociation of perceptual and motor inhibition processes through the use of novel computerized conflict tasks.

Efficient behavioral functioning requires early perceptual inhibition of irrelevant stimuli and later motor inhibition of inappropriate responses. The Perceptual and Motor Conflict Tasks were developed to differentially assess perceptual and motor inhibition, and to determine whether these processes utilize separate or shared cognitive resources. The computerized tasks include six subtests involving a box or an arrow appearing in various locations. Subjects respond by pressing a key on the left or right side of a keyboard. In different subtests, arrow direction or stimulus location determines correct responses. Perceptual inhibition assessment requires the subject to respond to a conflicting arrow direction while ignoring stimulus location. Motor inhibition assessment involves the subject responding in the direction opposite to that indicated by a centrally located arrow. In a neurologically normal sample (N = 44), reaction time analyses yielded significant Perceptual and Motor Conflict main effects, with slower performance under conflict conditions, but no significant Perceptual x Motor interaction. The lack of a significant Perceptual x Motor interaction, according to the additive factor model, indicates that these two processes utilize distinct cognitive resources. Nevertheless, performance on the two conflict tasks was significantly correlated with each other, and Perceptual Conflict performance was significantly correlated with Stroop interference.