The Role of White Matter Integrity in Age-Related Language Production Differences
Open Access
- Author:
- Troutman, Sara B
- Graduate Program:
- Psychology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 13, 2018
- Committee Members:
- Michele Theresa Diaz, Thesis Advisor/Co-Advisor
Nancy Dennis, Committee Member
Lesley Ross, Committee Member - Keywords:
- Aging
Language
white matter - Abstract:
- Despite having equal comprehension ability, older adults have more language production difficulties than younger adults (Diaz, Johnson, Burke, & Madden, 2014). According to the Transmission Deficit Hypothesis, language difficulties stem from signal transmission failures which increase with age. The hypothesis holds that the one-to-one mapping of the phonological system creates vulnerability to transmission failures but the many-to-one mapping of semantic networks provides protection from effects of transmission failure (Burke and MacKay, 1991). Alternatively, the Inhibition Deficit Hypothesis would posit that age-related declines in inhibition increase the task-demands of speaking, leading to poorer performance (Hasher & Zacks, 1988). Since white matter integrity has been shown to mediate age-behavior relationships, a potential mechanism underlying both accounts may be age-related white matter integrity declines (Head et al, 2004; Bennet & Madden, 2014). This study explored the relationship between white matter integrity and age-related language deficits using Diffusion Tensor Imaging (DTI) to test hypotheses generated by the Transmission Deficit Hypothesis and the Inhibition Deficit Hypothesis. Findings supported the Transmission Deficit Hypothesis; white matter integrity declined across the brain but the relationship between white matter integrity and outcomes only manifest in phonological behaviors and phonological-task activation. Importantly, age mediated the relationships between white matter integrity and behavioral and activation outcomes, suggesting that white matter integrity decline is a substrate of age-related language production deficits.