Agrammatism is a language disorder characterised by a morphological and/or syntactic deficit in spontaneous speech. Such deficits are usually associated with comprehension disorders - though it is said that this is not always the case - which result in a certain degree of variability in syntactic, lexical, and morpholexical performance. The purpose of this study is to reconsider the nature of comprehension disorders in agrammatism, to test whether Grodzinsky's Trace Deletion Hypothesis (TDH) can be generalised to all agrammatic patients, and to ascertain whether the pattern of impairment observed in agrammatism differs from that present in fluent aphasic patients. Eleven agrammatic patients were tested by means of a sentence comprehension task comprising simple active and passive reversible sentences. The performance of the agrammatic patients was compared to that of 16 fluent aphasic (10 Wernicke's and 6 conduction) and 10 control subjects. The deficits observed in the agrammatic subjects were compatible with the TDH, but there was also impaired processing of pronouns (elements that are also subject to movement) and a mild deficit on the processing of simple active sentences. The fluent aphasic patients showed a similar pattern of impairment. A logistic regression analysis was then applied to each single case separately, in order to study the homogeneity of the patients' performance within each aphasic subgroup. Of the 11 agrammatic patients, 3 did not show comprehension disorders, 5 had a specific deficit for passive movement, 1 a lexical deficit for pronouns only, and 1 a pattern of impairment compatible with Linebarger et al.'s trade-off theory. The last patient showed a deficit for simple active reversible sentences compatible with damage to the mapping of grammatical functions to thematic roles. Similar patterns of impairment were also found in the fluent aphasic sample. Overall, the results lead to the conclusion that the TDH cannot be generalised to all agrammatic patients, that the mechanism it invokes is not the only source responsible for agrammatic comprehension disorders and also contributes to comprehension disorders in fluent aphasic patients.
University of Milan-Bicocca, Italy 2:
International School for Advanced Studies, Trieste, Italy 3:
G. Salvini General Hospital, Rho, Italy 4:
S. Maugeri Foundation, Veruno, Italy 5:
S. Maugeri Foundation, Montescano, Italy