Connectionist diagnosis of lexical disorders in aphasia

Background: In the cognitive neurolinguistic approach to lexical deficits in aphasia, impaired levels of processing are localised in a cognitive model. Model-oriented treatment may target these impaired components. Thus a precise assessment of the disorder is crucial. Connectionist models add to this by using computer simulation to specify the details of the functioning of these components. The connectionist semantic-phonological model of lexical access (Dell, Martin, & Schwartz, 2007; Schwartz, Dell, Martin, Gahl, & Sobel, 2006) explores the impairment by simulating error patterns in naming and repetition. Aims: The purpose of the present study was to investigate the model's range of application as a diagnostic tool, and to derive recommendations for the model's use in clinical settings. Methods & Procedures: We demonstrate how we adapted the error analysis to 15 German-speaking patients with aphasia, analysed the model's accuracy in assessing naming and repetition disorders, and explained deviations between the error pattern produced by each patient and the one produced by the model's simulation by appealing to an extended version of the model. Outcomes & Results: Overall, the model yielded good fits of the patients' error patterns. Larger model-patient deviations could be explained by the model's limited set of lesionable components. Conclusions: The connectionist diagnosis of naming and repetition disorders in the semantic-phonological model is a reasonable tool in model-oriented assessment. However, the diagnosis needs to be complemented by further language tests.