Graduation Year

2007

Document Type

Dissertation

Degree

Au.D.

Degree Granting Department

Audiology

Major Professor

Jacqueline J. Hinckley, Ph.D.

Keywords

Lexical access, Stroke, Network, Negative priming, Semantic associates

Abstract

Lexical retrieval models illustrate both activation and inhibition between concepts, words, and phonemes. When semantic activation spreads from one concept to its related concepts, inhibition is recruited so that competition between related concepts can be overcome and a target production achieved. Persons with aphasia often exhibit difficulty with producing the desired response, which could be the result of inadequate inhibitory processes to overcome response competition. Inhibitory processing is typically measured using a negative priming task. Twenty participants with aphasia, twenty-five young participants, and twenty age-matched aphasia group controls were recruited for this study. Participants with aphasia completed a picture-naming task, two written lexical decision tasks, subtests of an aphasia assessment, and the negative priming lexical decision task. Control groups completed only the negative priming task. This task consisted of 4 blocks of 72 trials each in

which target words were related associates (RA), related distractors (RD), or unrelated (UN), or pseudowords. Results indicate that no groups showed predicted decreased reaction times to the RA condition. Instead of showing the fastest reaction times, the average RTs in the RA condition were between those in the RD and the UN conditions. Error rates were higher in the aphasia group, with significantly more errors for related conditions. In the young control group, significant negative priming was achieved. However, in the aphasia and aphasia-control groups, there was no significant negative priming. Multiple regression analysis determined that time post onset, age, education, type of fluency, and classification of anomia were not significant predictors of these results in the aphasia group. It is argued that these results are not strategically induced secondary to expectancy or a semantic expectancy or a semantic-matching process. Using a prospective or a retrospective strategy would be

useless since only a small portion of the prime-probe pairs are directly related. The results of the aphasia group and the aphasia-control group are similar to those found in the aging negative priming literature, but it is unclear if this should be interpreted as degraded inhibitory processes. Future studies to further explore negative priming in aphasia are discussed.

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