Response Time Consistency: Correspondence with Cognition and the Effects of Training and White Matter Lesion Volume
Year: 2017
Type: dissertation
Abstract: Response time consistency or, intraindividual variability (RT IIV) from trial to trial, is known to increase with age and is exaggerated in people with neurological dysfunction. RT IIV is thought to index the fidelity of executive control mechanisms necessary for sustaining attention. Conventionally measured RT IIV conveys variability about the entire distribution. An ex-Gaussian approach segments distributional properties into normal distribution and exponential components; evidence shows that the portion of the distribution containing only extremely slow responses (ex-Gaussian parameter tau) is elevated with executive control deficits. Thus, tau may be a critical factor in the measurement of RT IIV. In a series of studies, I examined response time distribution indices with two main goals: the first was to explore the association with cognition (Studies 1, 2, and 4), and the second was to investigate the malleability of variability (Studies 3 and 5). In Studies 1 and 2, data from healthy participants were gathered from response time tasks and neuropsychological tests and subjected to structural equation modeling (SEM). SEM revealed strong associations between distributional parameters (mu and tau) and different cognitive domains. Study 4 investigated the role of white matter lesions in response time performance, revealing that greater lesion volume was negatively association with general slowing and extremely slow responding. For my second goal (investigating malleability of RT IIV) in Study 3, I applied a training procedure to healthy young and older adults. I found RT IIV reductions in participants who received feedback training, but not in participants who received a comparison control condition. Furthermore, the ex-Gaussian parameter tau was specifically reduced by training. Study 5 involving older adults with a range of white matter lesion severity showed non-significant effects for feedback training, likely due to low power. Visual inspection, however, revealed a pattern of tau reduction in the feedback group only. Overall, my dissertation research provides further support for the notion that RT IIV, and more specifically tau, is an indicator of executive control. The training studies suggest a potential avenue for attentional repair in both healthy and brain compromised individuals.
Source: TSpace (University of Toronto)
Author: Brandon P. Vasquez
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2796964117