Agrammatism

"Agrammatism is a disorder that primarily affects spoken language production."

Agrammatism is a term commonly used to describe the speech of non-fluent aphasics. It can be said to be characterised by three aspects of speech deficiency. The patient has difficulty forming sentences correctly and tends to simplify if required to repeat phrases with complex syntax. Not all parts of speech are affected equally; grammatical elements are impaired selectively, resulting usually in the retention of content words but not function words or word endings. Lastly, although it was believed that patients' comprehension was intact, there is evidence that agrammatic speakers have problems in comprehending sentences with complex syntax Ð'- in which case the disorder would not be confined purely to language production. This is a matter for debate, but equally pertinent to the discussion is the question of whether agrammatism can be described as a coherent deficit; some have argued that the symptoms exhibited by non-fluent aphasics differ in way such as to render such classifications as Ð''agrammatic' as unhelpful and irrelevant.

Attempts to explain the symptoms of agrammatism have taken into consideration the articulation problems experienced by aphasics: the elimination of function words might be a result of a conservation of resources by restricting output to words with lexical meaning. However, this cannot possibly serve as an explanation for the whole disorder, as the symptoms indicate the existence of deficiencies at the level of syntactic planning. Other hypotheses have suggested the dissociation in the processing of function and content words, and that Broca's area is responsible for dealing with grammatical elements, such as function words . Biassou et al., 1997, found that in a reading task French-speaking aphasics stumbled more frequently over function words than over content words. Kean (1977) related this to phonological deficiency and proposed that aphasics' omissions are the unstressed elements of phonological words, which results in the function words and affixes being lost. However, this does not explain the difficulties with sentence construction which are characteristic of agrammatism.

Schwartz' application of Garrett's model of sentence processing (1987) to agrammatism located the problem in the progression from the functional level to the positional level. A disorder here would prevent the speaker from creating a sentence frame and from retrieving the appropriate grammatical elements; both features are observed in agrammatics. The model does not offer an explanation of any comprehension deficits, as it relates only to language production; damage to another system would have to occur in order for this to be affected as well.

Evidence that agrammatics have comprehension difficulties in the case of complex syntax has been advanced by a number of researchers (Caramazza & Berndt, 1978, Caramazza & Zurif, 1976 and Saffran, Schwartz & Marin, 1980) who tested the ability of patients to match sentences with pictures when the semantic clues are removed. In particular, they found it difficult to identify passive constructions which were reversible, and to comprehend object relative constructions. One hypothesis which explains agrammatic comprehension problems is the trace-deletion hypothesis put forward by Grodzinsky (2000). He has suggested that problems of understanding arise from the inability to assign relations to elements of a sentence when the usual syntactic order has been changed and its traces are not present. However, despite the poor comprehension of the patients in the task mentioned above, a study of agrammatics by Linebarger, Schwartz and Saffran (1983) showed that they were able to perform well when asked to judge if a sentence was grammatical or not. Only a few structures, which involved the agreement of constituents across the sentence, presented problems Ð'- for example "the people will arrive at eight o'clock, didn't they?" This seems to suggest that these agrammatics can compute sentence structure, but cannot always access it actively, especially where thematic roles are involved. Another explanation, the mapping hypothesis, postulates the idea that parsing at a low level is intact, but the next stage is problematic. Agrammatics make use of semantic constraints to resolve questions of thematic role assignment, but not always correctly (they often fail to identify incongruency in sentences such as "the cheese ate the mouse").

Finally, a third theory has attributed the problem suffered by aphasics is due to general memory impairment. Sufferers with difficulties comprehending syntax do not