Ideomotor apraxia: behavioral dimensions and neuroanatomical basis.

Ideomotor apraxia, disordered movement execution to command, commonly follows left-hemisphere damage, implying left-hemisphere dominance for certain kinds of movements. To delineate this dominance we used different command modalities to elicit meaningful movements and tested imitation of nonsense movements. Twenty-seven patients with unilateral hemispheric stroke and 10 age-matched controls were evaluated. Patients with left-hemisphere damage performed both meaningful and nonsense movements poorer than the other study groups; thus, the meaningfulness of the movements is irrelevant for the left-hemisphere motor dominance. The performance varied, however, with the command modality and movement type. Based on this and earlier studies we posit that the left-hemisphere motor dominance is determined by the artificiality of the test situation (it concerns movements performed to command and out of the natural context) and increased spatial and temporal complexity of the demanded movements. No association between the lesion locus within the left hemisphere and the severity of the ideomotor apraxia was found.