Frontal cortex and the programming of repetitive tapping movements in man:lesion effects and functional neuroimaging

Two studies examined the contribution of human frontal cortical areas to th e programming of trains of repetitive movements. The first study compared t he performance of patients with unilateral frontal excisions, unilateral te mporal excisions and controls on the speed of initiation of discrete vs, se quential tapping movements to visual stimuli. The frontal group showed norm al initiation times in single taps and a normal execution (pace and accurac y) in sequential taps but they were slower than the other groups at initiat ing sequential taps indicating a sequence programming problem for repetitio ns of a single response. A second study examined the functional anatomy of single and sequential taps in eight control subjects using fMRI. Subjects p erformed flexion/extension movements of the right thumb at either 1 movemen t/s or as trains of four closely spaced movements at a rate of 1 train/4 s. Statistical analyses revealed that primary sensorimotor cortex and a dorso lateral premotor cortex region were activated in both conditions, Medial fr ontal activation was not significant in discrete movements but was clearly present in sequential movements and involved SMA and cingulate regions bila terally. In addition, two other dorsolateral premotor foci of activation we re observed in the sequential taps condition. Results from these two experi ments converge toward establishing a significant role of dorsolateral and m edial premotor regions in the programming of trains of repetitive responses . (C) 1999 Elsevier Science B.V. All rights reserved.