A Computational Model of Semantic Memory Impairment: Modality- Specificity and Emergent Category-Specificity
CARNEGIE-MELLON UNIV PITTSBURGH PA ARTIFICIAL INTELLIGENCE AND PSYCHOLOGY PROJECT
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Brain damage can cause the selective loss of knowledge about living or nonliving things. This seems to imply that semantic memory is organized taxonomically, with different components specializing in representing knowledge about living and nonliving things. An alternative view of semantic memory is that it is organized by modality, with different components representing information from different sensorimotor channels. In this article we demonstrate how a modality-specific semantic memory system can account for category-specific impairments after brain damage. Specifically, in Experiment 1 we test and confirm the hypothesis originally put forth by Warrington, McCarthy and Shallice that visual and functional knowledge play different roles in the representation of living and nonliving things. We then describe a parallel distributed processing model of semantic memory in which knowledge is subdivided by modality into visual and functional components. In Experiment 2 we lesion the model and confirm that damage to visual semantics primarily impairs knowledge of living things, and damage to functional semantics primarily impairs knowledge of nonliving things. In Experiment 3 we demonstrate that the model accounts naturally for a finding that had appeared problematic for a modality-specific architecture, namely impaired retrieval of functional knowledge about living things.
- Medicine and Medical Research