Simulating single word processing in the classic aphasia syndromes based on the Wernicke-Lichtheim-Geschwind theory.
The Wernicke-Lichtheim-Geschwind (WLG) theory of the neurobiological basis of language is of great historical importance, and it continues to exert a substantial influence on most contemporary theories of language in spite of its widely recognized limitations. Here, we suggest that neurobiologically grounded computational models based on the WLG theory can provide a deeper understanding of which of its features are plausible and where the theory fails. As a first step in this direction, we created a model of the interconnected left and right neocortical areas that are most relevant to the WLG theory, and used it to study visual-confrontation naming, auditory repetition, and auditory comprehension performance. No specific functionality is assigned a priori to model cortical regions, other than that implicitly present due to their locations in the cortical network and a higher learning rate in left hemisphere regions. Following learning, the model successfully simulates confrontation naming and word repetition, and acquires a unique internal representation in parietal regions for each named object. Simulated lesions to the language-dominant cortical regions produce patterns of single word processing impairment reminiscent of those postulated historically in the classic aphasia syndromes. These results indicate that WLG theory, instantiated as a simple interconnected network of model neocortical regions familiar to any neuropsychologist/neurologist, captures several fundamental "low-level" aspects of neurobiological word processing and their impairment in aphasia.
Weems
Scott A
SA
Center for the Advanced Study of Language, University of Maryland, Box 25, College Park, MD 20742, USA. sweems@casl.umd.edu
Reggia
James A
JA
D001037:Aphasia / Q000503:physiopathology*; D001921:Brain / Q000033:anatomy & histology / Q000503:physiopathology*; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D009415:Nerve Net / Q000503:physiopathology*; D011582:Psychological Theory; D014825:Vocabulary