Frontal lesions impair the attentional control of movements during motor learning

This study examined the effects of frontal lobe lesions on the control of m ovements during motor learning. We compared the performance of patients wit h unilateral frontal or temporal excisions and controls in two-dimensional aiming movements during adaptation to a transformed visuomotor mapping. Sub jects tried to reach a fixed target on a graphics tablet using indirect vis ual control from a monitor in either: (1) the standard visuomotor mapping, (2) a full inversion of motor space preserving the axis of movement, or (3) a mirror-like inversion of one axis of motor space. In the standard mappin g, all groups showed precise and rapid aiming movements. In the full invers ion condition, frontal lobe patients showed a stronger tendency than others to initiate movements in the natural direction (capture errors) during ada ptation. In the mirror-like inversion, frontal patients showed deficits in both movement initiation and movement corrections. These control deficits d isappeared with practice. These data provide evidence for a critical role o f frontal cortex in the attentional control of unpracticed movements in man . (C) 1999 Elsevier Science Ltd. All rights reserved.