Category-specific deficits for grammatical classes of words: evidence for possible anatomical correlates.

Several neuropsychological studies have shown that brain-damaged patients may demonstrate category-specific deficits for grammatical classes of words, such as nouns and verbs. We describe 3 patients with selective impairments of these latter categories. The first patient, with marked atrophy of the left temporal lobe, was disproportionately impaired in naming and comprehension of nouns. The second patient, with a predominantly left frontal lobe atrophy, was selectively impaired in naming and comprehension of verbs. The third patient, with a left frontal lobe perfusion abnormality, had a selective impairment in naming and comprehension of verbs. Evidence from the present study support the hypothesis that anatomically distinct neural systems in the temporal and frontal lobes of the dominant hemisphere might play a critical role in lexical processing of nouns and verbs respectively.