Liepmann and Maas (1907) suggested that the left hemisphere contains movement formulas that program the timing and spatial relationships of skilled movements bilaterally. Although patients with ideomotor apraxia from the left hemisphere lesions made errors when gesturing to command or imitating a gesture, the nature of the errors made by these patients and its anatomic correlate have not been systematically analyzed. Patients with ideomotor apraxia may also have difficulty discriminating and comprehending gestures. The nature of these discrimination and comprehension defects have also not been fully explored. The purpose of this experimental program is to better define the gesture production and reception errors associated with ideomotor apraxia and see how these errors may relate to different anatomic lesions. This proposal contains five experiments. The first experiment examines the apraxic patients' production errors. Apraxic patients' production errors will be qualitatively and quantitatively analyzed and scored. The second study attempts to learn what parameters of a complex movement cause discrimination disorders in apraxic patients. The third experiment tests the hypothesis that apraxic subjects have more difficulty performing movements executed in extra-personal space than they do in performing movements in intra personal space. Experiment four attempts to learn if the gesture comprehension disorder exhibited by apraxic patients is related to a movement disorder or a language disorder. Experiment five examines how the dichotomy of abstract vs. concrete pertains to apraxic patients' performances.