Dissertations, Theses, and Capstone Projects

Date of Degree

6-2016

Document Type

Dissertation

Degree Name

Ph.D.

Program

Speech-Language-Hearing Sciences

Advisor

Loraine Obler

Committee Members

Jamie Reilly

Elizabeth Galletta

Keywords

semantic memory, tdcs, eye-tracking, anterior temporal lobes, confrontation naming

Abstract

Confrontation naming is a complex process that involves multiple stages and can be initiated through multiple modalities. Models of confrontation naming have implicated areas such as the anterior temporal lobe (ATL) and temporo-parietal junction (TPJ) for the semantic stage of naming. Transcranial direct current stimulation (tDCS) was used to modulate neural excitability in the bilateral ATLs and the TPJs to understand brain-behavior relationships involved in the semantic stage of confrontation naming. Effects of tDCS are often very small or non-existent when measured by reaction times and accuracy. Therefore the present study used more sensitive eye-tracking measures (first fixation duration and fixation time) in combination with reaction times to measure the effect of tDCS.

Twenty-four neurologically healthy native English speakers ranging in ages 18-30 took part in the study. Participants named 120 pictures and six-digit numbers both pre and post tDCS in three different sessions. Three sessions corresponded to three different brain regions targeted; bilateral ATLs, bilateral TPJs and Motor Cortex (MC) which served as a control site.

Analysis of eye-tracking and behavioral data revealed that application of tDCS over the bilateral ATLs increased first fixation duration and fixation time but decreased naming latencies. The results from the present study thus confirm the role of bilateral ATLs for the semantic stage of naming. However, no evidence for the role of TPJs for the semantic stage of naming was found. The present study also provides further support for the efficacy of tDCS and suggests that it is a viable tool for investigating neural bases of language/cognitive processes.

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