Undergraduate Honors Theses

Thesis Defended

Fall 2012

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Integrative Physiology

First Advisor

David Sherwood

Second Advisor

Kenneth Wright

Third Advisor

Albert Kim

Fourth Advisor

Marie Boyko

Abstract

We used Electroencephalography (EEG) to investigate whether context‐modulated lexical access occurs within the first 200 msec of stimulus onset. We employed two different presentation rates to investigate whether earlier effects (P130 and N170) as well as later effects (N400 and P600) are modulated by the rate of presentation of stimuli. Subjects read contextually supported controls, contextually supported pseudowords, contextually unsupported pseudowords, and nonwords (e.g., She measured the flour so she could bake a cake/ceke/fash/srdt), which were presented between subjects at either a fast rate (word appeared on screen for 200 msec followed by a 175 msec blank screen) or a slow rate (word appeared on screen for 200 msec followed by a 350 msec blank screen). We predicted that the supported pseudoword would have the earliest and largest effect, followed by the nonword and unsupported pseudoword. Our predictions were supported numerically but not statistically. We observed that presentation rate clearly modulated the N400 effect. Subjects who saw the fast presentation rate had a more negative N400 for nonwords compared to subjects who saw the slow presentation rate; however, this effect was nonsignificant as well. Although we found no significant effects, numerically our results support our hypothesis that context modulates lexical access prior to 200 msec and presentation rate can modulate word recognition effects.

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