| Context | The various forms of apraxia, according to Brown, reflect or point to stages in the ontogeny of a  motor act, and he has paralleled this with the view that the distinct  forms of aphasia characterize stages in the development of a linguistic production. According to Brown (1977), facial apraxia is a "disorder of  VOLITIONAL facial action appearing in performances initiated in the test  situation with no alteration of spontaneous facial motility. The more automatically elicited performances are better preserved, whereas actions elicited by written or spoken commands are impaired" (p. 72,  emphasis added). Much has been said about apraxia from supramarginal gyrus lesions (Brown, 1972; Denny-Brown, 1958; Geschwind, 1965; Mateer & Kimura,  1977). Predictably, those who admit of center-lesion explanations have considered supramarginal gyrus apraxia of speech. 
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