Efficacy of Pharmacological Treatment of Working Memory Impairment After Traumatic Brain Injury: Evaluation With fMRI

Overview

This study is designed to examine the effects of a wake-promoting agent (Modafinil) on working memory (WM) in persons with moderate to severe TBI utilizing a double blinded placebo controlled methodology. Our approach is to evaluate participants with BOLD fMRI and a limited neuropsychological battery to examine WM performance before and after pharmacological intervention. Hypotheses 1. Because increased cognitive effort (as a function of decreased efficiency after TBI) is presumed to underlie fMRI activation dispersion that is seen during central executive WM tasks, we anticipate an attenuation of cerebral activation in prefrontal cortex during pharmacological intervention with Modafinil when compared to placebo administration on the mPASAT and vigilance testing. 2. There will be a correlation between the decreased dispersion of the fMRI signal on scans and improvement in neuropsychological measures when individuals are on Modafinil that is not seen when they are taking placebo.

Work from our institution has shown that moderate and severe TBI subjects demonstrate an altered cerebral representation when they attempt to process a verbal WM task. Specifically, our data show a post-TBI pattern of activation that is dispersed and more lateralized to the right hemisphere, as compared to healthy controls. Taken together, we interpret these findings to mean that it is requires more cerebral resources for TBI subjects to process tasks that were previously more automatic. In other words, their processing is less efficient. This is consistent with TBI patients' self-reports of needing to expend greater cognitive effort to perform such tasks, both in the lab and in everyday life. Our preliminary data was the first step in understanding the cerebral substrate of these difficulties. However, simply indicating that individuals with TBI have a WM problem is not enough. The development of targeted interventions to ameliorate these deficits is the next step in the treatment process. The present proposal has important implications for TBI rehabilitation. One of the major goals of cognitive remediation is to help TBI patients learn new information more accurately and efficiently, and to improve their performance in activities of everyday life. 123 Because WM impairments are so prevalent in TBI, the present study can help to shed light on potential treatment alternatives for these potentially devastating problems. In spite of the prevalence and popularity of cognitive remediation strategies and procedures, there remains little empirical support for their efficacy, and virtually no understanding of the underlying neurocognitive processes that facilitate intervention. The ability to develop a potentially efficacious treatment modality, which has a solid foundation, would be immensely beneficial.