Human multiunit activity related to attention and preparatory set

The impulse activity of 183 multiunits was recorded from the premotor cortex, the caudate nucleus, the globus pallidus and the thalamus in 15 Parkinson's disease patients bearing inert gold electrodes implanted for diagnosis and therapy. The patients performed a task in which stimulus triplets (each consisting of two informational and one trigger stimulus) were presented. The patients initiated or inhibited actions (naming or counting) depending on the particular informational stimuli, thus allowing discrimination between different components of multiunit responses associated with attention and preparatory set and with disengagement from these states. The data indicate the existence of two overlapping circuits: one responsible for preparation for and assessment of the behavioral meaning of the stimulus and the other responsible for preparation for and performance of verbal action.