The relationships between context and conceptual access.

Abstract

An important question in the cognitive neuroscience of language regards the nature of the conceptual representations that make up semantic memory. Amodal accounts argue that conceptual representations of objects and their processing is functionally distinct from sensory or motor brain systems whereas sensorimotor theories maintain that they involve the same perceptual and action brain areas active in experience. In a break from current orthodoxy, this thesis seeks to explore if concepts and semantic processing are best considered as functionally grounded in sensorimotor systems and contextually sensitive. We report four studies using behavioural-psycholinguistic and neuroimaging techniques in healthy and clinical populations. In part 1 we show that online perceptual processing in the visual and olfactory modalities can interact with language comprehension, that lifetime sensory experience shapes the representational structure of object concepts, and that the outcome of semantic processing differs depending on an interaction of personal experience and people¿s immediate perceptual context. In part 2, we examine whether motor system degradation due to Parkinson's disease leads to impairments in processing manipulable objects compared to healthy controls. Counter to our predictions we do not observe behavioural differences in the way Parkinson's disease patients access the representations of manipulable objects, however, we report neuroimaging evidence suggesting that changes in people's motor capacities lead to measurable alterations in the way that they process action semantics, at the neural level. Taken together this thesis provides evidence that the content and format of the conceptual representations of objects is multimodal and grounded in sensory and motor brain systems and people's lifetime sensory and motor experience with objects shapes their representations in deeply personal ways. Therefore, contrary to amodal accounts, there is functional overlap between sensorimotor and semantic processing, such that sensory, motor and semantic processes mutually interact with context (at many levels). This suggests that exploring the relationship between concepts and context is both necessary and vital in order to properly understand the semantic representations underlying noun words.