Author Date

2021-08-06

Degree Name

Department

Psychology

College

Family, Home, and Social Sciences

Defense Date

2021-08-06

Publication Date

2021-08-06

First Faculty Advisor

C. Brock Kirwan

First Faculty Reader

Jared Nielson

Honors Coordinator

Bruce Brown

Keywords

handedness, fMRI research, memory lateralization, left-handed, Provo, right-handed

Abstract

About 11% of the world population is left-handed, a significant minority of the potential research participant pool for functional MRI (fMRI) studies. However, convention in fMRI research dictates these potential participants be excluded due to evidence that left-handed people (LH) may have different lateralization of neural functioning than right-handed people (RH). This difference in lateralization may cause different areas of the brain to be activated by the same task. The current study investigates the lateralization differences between N=26 LH and N=27 RH during encoding and recognition memory tasks for words and faces. Additionally, we measured participants' laterality index by administering a semantic fluency task. We found localized evidence of differential activation between LH and RH groups at both encoding and retrieval. To measure if including LH in fMRI studies would alter results significantly, we calculated memory effects in a priori regions of interest (ROI) for the RH only, and then examined the effect of substituting in progressively more LH for RH. We found that subsequent memory effects at encoding were not reduced by adding in LH. However, at retrieval, significant memory effects diminished in the bilateral precuneus for faces and in the left hippocampus for words when substituting in six and five LH, respectively. These findings suggest that while the blanket exclusion of LH in memory research is not warranted, exclusion for research in specific ROI may be justified.