CEREBRAL PROCESSES RELATED TO VISUOMOTOR IMAGERY AND GENERATION OF SIMPLE FINGER MOVEMENTS STUDIED WITH POSITRON-EMISSION-TOMOGRAPHY

Positron emission tomography was used to compare the functional anatom y of visual imagination and generation of movement. Subjects were aske d to generate visual images of their finger movement in response to a preparatory signal. Four conditions were tested: in two, no actual mov ement was required; in the other two, a second signal prompted the sub jects to execute the imagined movement. Which movement to imagine was either specified by the preparatory stimulus or freely selected by the subjects. Compared with a rest condition, tasks involving only imagin ation activated several cortical regions (inferoparietal cortex, pre-s upplementary motor area, anterior cingulate cortex, premotor cortex, d orsolateral prefrontal cortex) contralateral to the imagined movement. Tasks involving both imagination and movement additionally increased activity in the ipsilateral cerebellum, thalamus, contralateral antero parietal, and motor cortex and decreased activity in the inferior fron tal cortex. These results support the hypothesis that distinct functio nal systems are involved in visuomotor imagination and generation of s imple finger movements: associative parietofrontal areas are primarily related to visuomotor imagination, with inferior frontal cortex Likel y engaged in active motor suppression, and primary motor structures co ntribute mainly to movement execution. (C) 1998 Academic Press.