Cerebral lateralization - Relationship of language and ideomotor praxis

Objective: To determine the relationship of language lateralization and han d preference to praxis performance following left and right hemispheric amo barbital-induced inactivations. Background: Patients who are aphasic from l eft cerebral dysfunction also frequently exhibit ideomotor apraxia in which they make temporal, spatial, and postural errors of learned skilled moveme nts. However, hemispheric lateralization of the systems mediating ideomotor praxis in patients with atypical cerebral language dominance (i.e., bilate ral or right hemispheric language function) remains uncertain. Methods: Sub jects included 90 patients with intractable seizures who were undergoing th e intracarotid amobarbital procedure (IAP) as part of their preoperative ev aluation for epilepsy surgery. Hand preference was determined by the Benton Handedness Questionnaire. Praxis was assessed by the subject's performance when pantomiming the use of four pictured tools. Results: During left IAP, patients with typical language dominance made more ideomotor apraxic error s than did patients with atypical language dominance. During right IAP, pat ients with atypical language dominance made more ideomotor apraxic errors t han did patients with typical language dominance. Overall, patients with at ypical language dominance made fewer ideomotor apraxic errors than did pati ents with typical language dominance. These relationships were present irre spective of hand preference. Conclusions: Language dominance is more closel y associated with the laterality of temporal and spatial movement represent ations (i.e., ideomotor praxis dominance) than is hand preference. Patients with atypical language dominance exhibit more bilateral cerebral distribut ion of both language and praxis function.