Distinguishing the neural bases of lexical access

University Of Iowa, Iowa City IA

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Abstract

DESCRIPTION (provided by applicant): This research proposes to distinguish the neural correlates of phonological and semantic aspects of lexical (word-level) access. Studies of patients and functional neuroimaging studies of unimpaired subjects have implicated left-sided perisylvian (inferior frontal gyrus (IFG), posterior superior temporal gyrus (pSTG)) and extrasylvian (inferotemporal cortex (IT)) brain areas in lexical access. The specific aims of this application are: 1) To identify the neural systems involved in accessing lexical phonology; and 2) To identify the neural systems involved in accessing lexical semantics. Phonological word form (lexical phonology) access has been shown to be modulated by word frequency. With respect to aim 1, we hypothesize that producing lower frequency words will correlate with longer reaction times and greater fMRI activation in left superior IFG, pSTG, and regions of IT. With respect to aim 2, we hypothesize that processing more ambiguous words will correlate with longer reaction times and greater fMRI activation in the inferior region of IFG as well as more inferior areas of IT partially overlapping those associated with phonological access. This study should lead to a more complete neural account of lexical access.