Event-related potentials (ERPs) will be recorded from the scalp of normal human subjects in response to linguistic stimuli. The main focus will be upon studies of late negative ERP components elicited during language processing. In particular, an N400 component has been observed in response to words that are incongruent or unexpected in relation to a prior semantic context. Current evidence suggests that the N400 is a physiological index of the priming of the semantic representation of verbal stimuli. The proposed experiments are aimed at clarifying the nature of semantic information processing that is reflected in these late ERPs.
The specific aim of the separate experiments are: (1-3) To ascertain whether the ERP correlates of semantic priming are signs of automatic and/or attentional processing; (4) To examine the ERPs to strong syntactic violations; (5) To use ERPs to evaluate the timing of phonemic and semantic analyses of homophones; (6) To assess the obligatory and optional aspects of sematnic and phonemic priming processes; (7) To determine the extent to which the sematic processing reflected by the N400 is modality-independent by examining ERPs to anomalous information presented in the form of line drawings; (8) To compare the sematic processes utilized by bilinguals in their first and second languages; (9) To use lexical decision latencies and ERPs in concert to determine whether all meanings of an ambiguous word are accessed and to measure the time course of their activations; (10) To test our hypothesis of the respective roles of semantic priming and elaboration in cued recall; (11) To compare the processing of completely nonsensical anomalies and literal anomalies with a metaphorical interpretation. This research project will identify and refine electrophysiological measures of important cognitive functions related to language comprehension and memory organization in normal, young adult subjects. This normative data base should be of value for the future evaluation and analysis of disorders of reading, language understanding and learning.
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