Impaired grammar with normal fluency and phonology. Implications for Broca's aphasia.

Extensive testing of grammatical function, including assessment of spontaneous language, inflectional morphology, ability to produce grammatical structures, syntactic comprehension and grammatical judgement, was carried out in 2 patients with large dominant frontal lobe lesions, including but not confined to, the third frontal convolution. Both patients were fluent and had normal articulation and phonological production and neither was agrammatic, suggesting that even very large frontal lesions do not produce Broca's aphasia and that language cortex proper is confined to the postcentral perisylvian region. Both patients were impaired in the use of more complex syntactic structures and one, who in addition had severe generalized impairment in frontal lobe function, also had impaired judgement regarding the use and placement of functors. These data provide further support for the dissociability of syntactic and morphological aspects of grammar in aphasic patients and, together with other studies, link these functions with the frontal lobe and the postcentral perisylvian cortex, respectively. The sparing of grammatical judgement in 1 patient, despite a very extensive lesion, suggests that very large portions of the frontal lobe are involved in grammatical function. The nature of frontal lobe function in syntax appears to be congruent with the role of the frontal lobes in other aspects of behaviour.