Ideational Gestures and Speech in Brain-damaged Subjects

Patterns of speech-related ("coverbal") gestures were investigated in two groups of right-handed, brain-damaged patients and in matched controls. One group of patients ("aphasic") had primarily anomic deficits and the other ("visuo-spatial") had visual and spatial deficits, but not aphasia. Coverbal gesture was video-recorded during the description of complex pictures and analysed for physical properties, timing in relation to speech and ideational content. Aphasic patients produced a large amount of ideational gestures relative to their lexical production and pictorial input, whereas the related production of the visuo-spatial patients was small. Controls showed intermediate values. The composition of ideational gestures was similar in the aphasic and control groups, while visual subjects produced less iconic gestures (i.e. less gestures which show in their form the content of a word or phrase). We conclude that ideational gestures probably facilitate word retrieval, as well as reflect the transfer of information between prepositional and nonpropositional representations during message construction. We suggest that conceptual and linguistic representations should probably be re-encoded in a visuo-spatial format to produce ideational gestures.