Motor perseverations: a function of the side and the site of a cerebral lesion

Motor perseverations are commonly thought to be a sign of frontal lobe lesions, although they may also occur following lesions outside the frontal lobes. Moreover, differences in the type and frequency of motor perseverations between the two cerebral hemispheres have been suggested. Recurrent perseverations (repetition of a previous response to a subsequent stimulus) and continuous perseverations (abnormal prolongation of a current activity) are two different aspects of motor intentional disorders. The former have been associated with left hemispheric lesions, and the latter with right hemispheric lesions. To test this hypothesis, we examined 42 patients with single cerebral lesions of different locations: 22 right hemispheric (7 frontal and 15 extrafrontal) and 20 left hemispheric lesions (8 frontal and 12 extrafrontal), and healthy controls with a graphic task, allowing for analysis of these two types of motor perseverations. We found that (i) both types of perseverations increased significantly for all groups of patients compared to normal controls, except for recurrent perseverations in patients with right posterior lesions, (ii) there was no significant dissociation between the type of perseverations and the side of lesions, and (iii) there was a significant interaction between the type of perseveration, frontal versus extrafrontal location, and the side of a lesion, which is based on the tendency for recurrent perseverations to be increased in left posterior and right frontal lesions, and decreased in left frontal and right posterior lesions, as compared to continuous perseverations. These findings cast doubt about the predominant role of the frontal lobes for motor perseverations, but support the idea of hemispheric specialization in motor control which is, however, more complex than previously thought.