Published In JOURNAL OF COGNITIVE NEUROSCIENCE, 7. Systematicity and Specialization in Semantics: A Computational Account of Optic Aphasia

AbstractOptic aphasic patients are selectively impaired at naming visu-ally presented objects but demonstrate relative intact compre-hension of those objects (e.g., by gesturing or categorization) and are able to name them when presented in other modalities (e.g., via tactile input). This and other modality-specific nam-ing deficits have been taken as evidence that semantics is or-ganized into distinct modality-specific subsystems. We adopt an alternative view in which semantics is a set of learned, in-ternal representations within a parallel distributed processing system that maps between multiple input and output modal-ities. We account for the critical aspects of optic aphasia in terms of the effects of damage to such a system, despite its lack of modality-specific specialization. We show that the ro-bustness of a task in such a system depends critically on its systematicity, and that modality-specific naming deficits can arise because naming is an unsystematic task