A redefinition of the syndrome of Broca's aphasia: Implications for a neuropsychological model of language

ABSTRACT A neuropsychological theory is offered to account for the syndrome of Broca's aphasia. A critical review of the literature, with emphasis on recent research, provides the basis for a redefinition of the syndrome that considerably broadens its classical description. The argument is advanced that the focus of neuropsychological explanation should be on theoretically separable psychological mechanisms that might be disrupted in relative isolation from other components in conditions of focal brain damage, rather than on isolated units of aphasic performance. The symptoms that characterize Broca's aphasia are explained as predictable behavioral manifestations of a central disruption of the syntactic parsing component of the language System, coupled with a (theoretically independent) articulatory deficit that affects only the speech output System. The neuroanatomical implications of this argument are considered within the framework of the classical “strong localizationist” hypothesis.