A Semantic Locus for Refractory Behaviour: Implications for Access Storage Distinctions and the Nature of Semantic Memory

Abstract

A single case study is presented of a global aphasic patient, JM, who shows similar impairments to other patients in the literature classified as "access dysphasics": On auditory word-written word matching tasks, JM's performance is inconsistent, it declines over repetitions, and it is sensitive to presentation rate and to the semantic relatedness of distractors (Forde & Humphreys, 1995). The deleterious effects of stimulus repetition can be attributed to JM's access to semantic information becoming refractory following activation of a target word or object. This paper examines the locus of the refractoriness by comparing JM's performance on tasks requiring access to presemantic perceptual representations or to semantic information. When both words and pictures were used as stimuli, JM was unimpaired on tasks thought to tap presemantic representations, such as visual lexical decision and unusual views matching, but performance became refractory on tasks that required access to fine-grained semantic information about specific items (e.g. associative matching). In addition, we found that the refractoriness spread across modalities when the targets changed from pictures to words. We discuss the implication of these findings for understanding the underlying nature of semantic representations of words and objects, and for the access-storage distinction in neuropsychology.