White Matter Integrity And Age Related Differences In Reaction Time Components

WHITE MATTER INTEGRITY AND AGE RELATEDDIFFERENCES IN REACTION TIME COMPONENTSbyYIQIN YANGDecember 2013Advisor: Dr. Naftali RazMajor: PsychologyDegree: Doctor of PhilosophyReduced speed in information processing is a well-documented phenomenon associatedwith advanced aging. Age-related deterioration in white matter integrity might play a role in age-related increase in reaction time (RT). However, the association between microstructuraldifferences in particular white matter regions or tracts with RT is unclear. Decomposing RT intoparts might be a better way to understand the relationship due to multiple processes involved inRT. In a lifespan sample of 90 healthy normotensive participants, this study examined theassociation between RT components derived from the Ratcliff diffusion model with age relateddifference in DTI indices of a wide variety of white matter tracts in both normal-appearing andwhole white matter. The results revealed that advanced age was associated with lower drift rate,greater response conservativeness and longer non-decision time. Age-related reduction in FA andincrease in MD was observed in most examined white matter tracts in both normal-appearing andwhole white matter. Even in healthy normotensive adults, WMH burden could account for partof variance between age and DTI indices. Greater age-related difference in white matter integrity