[Clinical and cognitive study of apraxia in cortico-basal atrophy. A selective disorder of the production system].

The aim of this study was to characterize the different processes underlying apraxic disorders in cortico-basal degeneration. Three patients were submitted to a prospective paradigm elaborated in the theoretical framework proposed by Roy and Square (1985). This cognitive model postulates a two-steps system in the control mechanisms in limb praxis: the conceptual system and the production system. Our results, strictly similar for the three patients, showed a sparing of the conceptual system and an impairment of the production system with a dramatic lack in the control of the temporal and spatial aspects of the gestures. These results suggest a dysfunction of the premotor cortex including the supplementary motor area.