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Lexical access in aphasic and nonaphasic speakers
G S Dell1, M F Schwartz, N Martin
1Beckman Institute, University of Illinois, Urbana 61801, USA. gdell@s.psych.uiuc.edu
Psychological Review
|October 24, 1997
Summary
This study models lexical retrieval in aphasia using a 2-step theory. Altering a normal processing model explains diverse naming errors in aphasic patients.
Area of Science:
- Psycholinguistics
- Computational Neuroscience
- Neurolinguistics
Background:
- Lexical retrieval, the process of accessing words, is impaired in aphasia.
- Understanding aphasic errors informs theories of normal language processing.
Purpose of the Study:
- To apply a 2-step theory of lexical retrieval to explain picture-naming errors in aphasia.
- To model the impact of simulated neural 'lesions' on language processing.
Main Methods:
- Utilized a computational model based on spreading activation in a lexical network.
- Parameterized the model for normal error patterns, then altered parameters ('lesioned') to fit aphasic error patterns.
- Derived and tested predictions regarding syntactic categories, phonological effects, recovery, and repetition tasks.
Main Results:
- The lesioned model successfully fit the error patterns of 21 fluent aphasic patients.
- Predictions derived from the model regarding syntactic influences, phonological effects, and recovery were confirmed.
- The model accurately predicted performance on single-word repetition tasks.
Conclusions:
- Simple quantitative changes to a normal lexical retrieval model can account for varied aphasic error patterns.
- This supports a connectionist approach to understanding language deficits in aphasia.
- The findings offer insights into the neural underpinnings of word production and retrieval.