Clinical aspects of premotor function.

Observations on patients with frontal lesions including the premotor cortex but not the primary motor cortex as shown by CT scans have shown a slight or moderate weakness of the contralateral shoulder or hip muscles which remained as a permanent deficit. The second deficit was an incoordination between movements requiring temporal adjustment between proximal muscle activities of both sides (limb-kinetic apraxia). From the clinical examination there was no evidence for deficient sensory guidance of movement. Visual control of hand and finger movements was normal as long as the arm could be supported during the tasks. In contrast, gross abnormalities of visually guided reaching (visuomotor ataxia) or somesthetic movement control (tactile apraxia) are seen after parieto-occipital lesions. On the basis of clinical observations it is therefore more likely that sensory-motor integration and transformation already takes place at the posterior lobes, where corresponding disturbances are pronounced but are absent after frontal lobe lesions.