Dissertations, Theses, and Capstone Projects

Date of Degree

6-2024

Document Type

Thesis

Degree Name

M.S.

Program

Cognitive Neuroscience

Advisor

Timothy Ellmore

Subject Categories

Cognitive Science

Keywords

fornix, visual memory, recognition memory, fMRI, diffusion tensor imaging, fractional anisotropy

Abstract

The fornix of the hippocampus may play an important role in working and long-term visual recognition memory. Data from a study on the role of hippocampal subfields in visual recognition memory was used here in conjunction with diffusion tensor imaging of the fornix to assess the relationship between the fornix integrity and behavioral performance, including percentage correct and reaction times. Two tasks were employed to separately evaluate working and long-term visual recognition memory, using a combination of indoor and outdoor naturalistic scenes and everyday objects. The subjects included 32 healthy adults, aged 18-44 years whose tensor imaging tractography was obtained with a Siemens 3 Tesla Prisma MRI Scanner to generate T2 weighted images. Analysis of fornix integrity was based on the total number of white matter fiber tracts, average length and diameter of the tracts, fractional anisotropy, mean diffusivity, average diffusivity, and radial diffusivity, with regions of interest (ROIs). of the left and right fornix. The percentage of correct responses served as a measure of memory performance. The difference in the average reaction time between trial 1 and 3 on a working memory task for old and new, and separately for “old” versus “new” items on the long-term memory task items served as additional measures of performance. A negative correlation (p =.035) was found between reaction time for new images presented during the recognition task and fractional anisotropy of the combined left and right fornix, with the model being significantly enhanced by adding age as a co-variate. There was also a positive correlation (p =.041) between reaction time and accuracy for new images in the recognition task. Evaluation of the current results in the context of existing literatures suggests that the fornix may play a role in the hippocampal memory system that, in concert with the “cognitive control network,” support the coordination between attention and visual recognition memory.

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