Observation of Motor Control in Patients with Partial and Complete Callosal Section

Abstract

The understanding of the execution of purposeful movement has been influenced by studies of brain-damaged patients. In the most striking instance, called an apraxic syndrome, patients have normal general intellectual abilities, motor power, reflexes, and coordination, but are unable to execute motor acts when verbally instructed to do so (Hecaen and Albert, 1978, pp. 90–128). Apraxic patients may also have defective visual—motor abilities. For example, the patient may be unable to manipulate common objects appropriately or to imitate or mime motor acts (DeRenzi et al., 1982; Hecaen and Albert, 1978, pp. 90–128), yet be able to carry out the motor act without difficulty when there is a personally generated need to perform the movement (Hecaen and Albert, pp. 90–128; Jackson, 1932). Clearly, apraxia is not necessarily a unitary disorder, and the severity of an apraxic syndrome appears to depend on the nature of the motor act, the context in which the movement is to be performed, and the characteristics of the instructions that specify the movement (DeRenzi et al., 1980, 1982; Geschwind, 1965; Hecaen and Albert, 1978, pp. 90–128; Volpe et al., 1982).