Selective Learning in Adult Traumatic Brain Injury
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Being able to strategically prioritize learning is important, given the ever-increasing amount of information that we are exposed to daily. This is even more so for individuals whose memory is significantly affected by a traumatic brain injury (TBI). For people who are in the chronic stage post injury with mild-to-moderate dysfunction, standard neuropsychological batteries may not be able to properly measure the current deficits that interfere with their daily functioning or shed light on the problematic areas associated with the impairment. Integrative measures that assess the ability to manipulate multiple domains in order to perform certain complex tasks were suggested to more accurately describe the source of real-life difficulties of people with brain injury. Selective learning is an integrative measure of executive memory that requires people to selectively prioritize or inhibit information based on its relevance to a defined goal. There is a gap in the literature regarding selective learning performance and factors that contribute to performance differences in adult TBI. This dissertation had two overarching goals: 1) to understand the factors that contribute to differences in performance between people with persistent mild and moderate TBI-related dysfunction and healthy individuals and 2) to examine the sensitivity of selective learning to identify TBI sequelae compared to all of the associated standardized measures combined. In this dissertation, a large battery of cognitive measures was performed on 160 individuals (18-70 years of age) in the domains of selective learning, executive function and memory. The findings of these studies demonstrated that simple memory was a sufficient factor to explain selective learning performance of healthy people. However, even the combination of executive functions (working memory, inhibition, and switching with simple memory) was not fully adequate to explain the selective learning performance of people with TBI. The ability of the selective learning measurement alone was equal to, if not better than, the other measures combined at explaining TBI-related deficits. Moreover, closer inspection of integrative selective learning performance of people with TBI revealed four distinguishable cognitive profiles that are based on the degree of involvement of executive function and memory. The best selective learning performers were more likely to have both high executive function and memory. The worst selective learning performers usually exhibited both low executive function and memory. The two middle profiles of selective learning performance were characterized by members with high executive function but low memory (higher end) and those with low executive function and high memory (lower end). Of these latter two, the people in the ‘higher end’ group (high executive function combined with low memory) tended to be older than people in the other three groups. This finding implied that people with reduced memory span due to age may still be able to perform complex integrative tasks well, given that they employ high executive function. This is the first study with a large sample size and age range to investigate the factors that underlie selective learning differences between people with TBI and controls. The current findings demonstrate that after brain injury occurs, neither simple memory nor isolated executive functions are sufficient to explain the performance on the complex task of selective learning. Rather, it requires a combination of measurements (selective learning criteria) to elucidate differences in performance styles. I also found that selective learning alone is more sensitive to integrative impairment following TBI than all of the other instruments combined. Therefore, measurement of selective learning appears to be a promising approach for significantly improving our understanding and monitoring of persistent TBI-related deficits longitudinally. Selective learning instrument may also be a valuable tool with potential to inform design of the most effective treatments for people in various stages of TBI-related conditions.