Human motor planning, motor programming, and use of new task-relevant information with different apraxic syndromes.

Abstract

Patients with ideomotor apraxia (n = 2) or ideational apraxia (n = 2) after left brain stroke and patients with constructional apraxia (n = 2) after cerebrovascular accident of the right hemisphere, as well as 16 non-brain-damaged control subjects, were given a standardized simple motor task: they were asked to make triangular arm movements of specific size, configuration and spatial orientation without visual control. Motion was analysed three-dimensionally in great detail prior to and after kinaesthetic training using a triangular stencil, and 1 day later. The experiment was conceptualized to assess three aspects of motor behaviour: (i) motor planning, operationalized as specification of content parameters of the movement as a whole; (ii) motor programming, the specification of spatiotemporal parameters of movement segments; and (iii) the ability to make use of task-relevant information provided by the training. Patients with ideational apraxia showed signs of impaired motor planning: they had difficulty in selecting the body parts to be moved, and movement concept and configurational aspects were deficient. The kinaesthetic sensorimotor training given seemed not adequate to reduce behavioural deficits. Kinematic peculiarities of patients with ideomotor apraxia can be understood as deficits in programming movement elements. Submovements were more segmented, showed irregularities as well as additional, not-requested elements. Their impairments could be reduced by task-specific sensorimotor training. Patients suffering from visuoconstructive apraxia after right brain damage might have difficulties in making use of new sensorimotor information relevant for spatial-motor aspects, as suggested by training-induced behavioural impairment with a severely constructional apraxic patient.