Dépistage des troubles langagiers acquis ou dégénératives : Approche multimodale
Dr Eva KEHAYIAa, Mme Nancy AZEVEDOa, Dr Ruth Ann ATCHLEYb, Dr Paul ATCHLEYb, Dr Vasavan NAIRc
a Centre de recherche interdisciplinaire en réadaptation; McGill University, b University of Kansas, c Douglas Mental Health Institute; McGill University
Introduction: Off-line psycholinguistic and neurolinguistic studies point towards selective deficits in word processing and in the processing of lexicality (whether a word is a real word or not in one’s language) by individuals with language breakdown following acquired or degenerative neurological conditions. While such investigations tap on overt language performance, they may miss information on underlying deficits or the mechanisms that subserve word processing. Objective: to obtain a clearer understanding of word level language change in individuals with stroke and aphasia and in those with probable Alzheimer’s disease (AD). We present three experiments that probed word recognition and processing of lexicality in AD and in those with aphasia, using on-line behavioural psycholinguistic methodology (Experiments1-2) and electrophysiological methods (Experiment 3). Experiment 1: On-line visual simple lexical decision task probing simple and complex words in eight individuals with aphasia following unilateral stroke. Experiment 2: On-line visual simple lexical decision task probing lexicality in eight individuals with aphasia following unilateral stroke and in ten English-speaking individuals with probable AD. Experiment 3: ERP task eliciting components reflecting attentional focus and stimulus salience (P300 family) in ten individuals with probable AD. Healthy controls with similar age and education participated in all three experiments. Results, across the three experiments, reveal a population and task effect. In those with aphasia, a clear dissociation between off-line and on-line methods sheds light on the availability of underlying language representations even when overt performance may be deficient. For those with probable AD, in spite the seeming absence of difficulty with lexicality, results from the ERP task point towards a marked difference in processing when compared to healthy aging control participants thus signaling language changes that may accompany the onset of the disease. Conclusions: the triangulation of on-line behavioural and electrophysiological methodology can offer a more comprehensive understanding of language and communication change and deficits in acquired and degenerative neurological conditions. This knowledge can also provide important information that can guide therapy planning and treatment that may ultimately have an impact on the quality of life of the individuals concerned.
Mots clés : aphasia, Alzheimer's disease, word processing, lexicality, mental lexicon, communication, residual language abilities, on-line methods, ERPs