Consecutive Versus Return Motor Perseveration During Line Cancellation Task in Hemispatial Neglect

Abstract

Patients with neglect often repeatedly cancel the same targets, a form of motor perseveration (MP). There seems to be 2 types of MP, making uninterrupted multiple strokes for each target, consecutive MP (CMP) or return MP (RMP) where patients return to previously canceled targets and remark them. The purpose of this study is to learn whether these 2 forms of MP are dissociable. We studied 3 patients, 1 with primarily CMP, another with primarily RMP and a third with mixed CMP and RMP by having them perform the cancellation task with and without background movement. In the patient with primarily RMPs (patient 1), leftward background movement decreased the severity of the neglect and the perseveration. Rightward background movement increased both. In contrast to patient 1, who showed the correspondence between the severity of neglect and perseveration, the patient with both CMP and RMP (patient 2) and the patient with primarily CMPs (patient 3) did not show such correspondence. The different responses of CMP and RMP to the treatment of neglect suggest that different mechanisms account for these 2 forms of MP. Although RMP might be related to neglect induced aberrant approach behaviors, CMP seems to be related to a disengagement disorder.