Reward presentation reduces on-task fatigue in traumatic brain injury.

While cognitive fatigue is experienced by up to 80% of individuals with traumatic brain injury (TBI), little is known about its neural underpinnings. We previously hypothesized that presentation of rewarding outcomes leads to cognitive fatigue reduction and activation of the striatum, a brain region shown to be associated with cognitive fatigue in clinical populations and processing of rewarding outcomes. We have demonstrated this in individuals with multiple sclerosis. Here, we tested this hypothesis in individuals with TBI. Twenty-one individuals with TBI and 24 healthy participants underwent functional magnetic resonance imaging. Participants performed a task during which they were presented with 1) the Outcome condition where they were exposed to monetary rewards, and 2) the No Outcome condition that served as the control condition and was not associated with monetary rewards. In accordance with our hypothesis, results showed that attainment of rewarding outcomes leads to cognitive fatigue reduction in individuals with TBI, as well as activation of the striatum. Specifically, we observed a significant group by condition interaction on fatigue scores driven by the TBI group reporting lower levels of fatigue after the Outcome condition. fMRI data revealed a significant main-effect of condition in regions previously implicated in outcome processing, while a significant group by condition interaction was observed in the left ventral striatum as revealed by a priori region of interest analysis. Results suggest that a salient motivator can significantly reduce fatigue and that outcome presentation leads to increased activation of the ventral striatum in TBI. These findings can inform the development of future non-pharmacological cognitive fatigue treatment methods and contribute to the growing body of evidence showing the association between cognitive fatigue and the striatum.

Corticostriatal Hyperactivation to Reward Presentation in Individuals With TBI With High Depressive Symptomatology: A Pilot Study.

OBJECTIVE: To examine the impact of depression on neural mechanisms associated with outcome processing (rewarding and punishing outcomes) in persons with traumatic brain injury (TBI). SETTING: Kessler Foundation's Rocco Ortenzio Neuroimaging Center. PARTICIPANTS: A total of 16 adults with moderate to severe TBI. MAIN MEASURES: Chicago Multiscale Depression Inventory (CMDI); Behavioral Inhibition/Behavioral Activation Scale (BIS/BAS); functional MRI of the head while performing a gambling task, with a reward (+$1.00) and punishment (-$0.50). RESULTS: Individuals with TBI reporting high depressive symptomatology exhibited increased activation in the ventromedial prefrontal cortex (VMPFC) and striatum during presentation of rewarding outcomes compared with individuals with TBI reporting low depressive symptomatology. Punishing outcome presentation was not associated with any change in brain activation. No differences in volume of the striatum and VMPFC were observed between groups. CONCLUSIONS: Current findings provide the first evidence of differences in neural mechanisms underlying outcome processing between individuals with TBI with and without depression. The results suggest that depressive symptomatology might have a different effect on individuals with TBI than what is typically observed in individuals without TBI reporting with depression, with the possibility of rewards becoming more reinforcing as depressive symptomatology increases. Future studies should explore the potential implications of behavioral responses to rewards and punishments in TBI and how they can affect rehabilitation approaches and activities of daily living.

Neural Correlates of Outcome Anticipation in Multiple Sclerosis.

Outcome anticipation is not only a mental preparation for upcoming consequences, but also an essential component of learning and decision-making. Thus, anticipation of consequences is a key process in everyday functioning. The striatum and the ventromedial prefrontal cortex are among the key regions that have been shown to be involved in outcome anticipation. However, while structural abnormalities of these regions as well as altered decision-making have been noted in individuals with multiple sclerosis (MS), neural correlates of outcome anticipation have not been explored in this population. Thus, we examined the neural correlates of outcome anticipation in MS by analyzing brain activation in individuals with MS while they performed a modified version of a card-guessing task. Seventeen MS and 13 healthy controls performed the task while functional magnetic resonance imaging (fMRI) was obtained. To achieve maximal anticipatory response and prevent the possibility of differential performance on the task, participants were presented with monetary rewards only on 50% of the trials. While replicating previous evidence of structural abnormalities of the striatum in MS, our results further showed that individuals with MS exhibited greater activation in the putamen, right hippocampus, and posterior cingulate cortex during outcome anticipation compared to healthy controls. Furthermore, even though there was no strategy that participants could learn in order to predict outcomes, 76% of participants with MS indicated that they used strategies while performing the task. We thus propose that the increased neural activation observed in MS during outcome anticipation might be explained by a failure in recognizing the lack of regularity in the task structure that could result in using strategies to perform the task.

Impact of frontal neurobehavioral symptoms on employment in individuals with TBI.

OBJECTIVE: To explore the contribution of frontal systems behavioral dysfunction on employment outcomes in individuals with traumatic brain injury (TBI), in the context of relevant predictors of work status. METHOD: Forty-two participants with history of moderate-to-severe TBI were classified as either "Employed" or "Unemployed." Groups did not differ on most demographic or injury variables, although the Unemployed sample reported greater symptoms of depression, pain, and fatigue (ps < 0.05). Participants completed a neuropsychological evaluation emphasizing frontal systems and Frontal Systems Behavior Scale (FrsBe; self- and informant-rated forms). RESULTS: T tests using cognitive indicators of frontal dysfunction revealed no significant differences between groups (ps > 0.05). T tests using neurobehavioral indicators of frontal dysfunction (i.e., FrSBe) revealed differences between groups on both self- (Hedge's g = 0.71; p = .046) and informant-rated (g = 1.12; p = .001) FrSBe total T scores. Two logistic regressions for each FrSBe score were conducted, including relevant variables on which samples differed as covariates. Only the informant-rated FrSBe score remained a significant predictor of employment (FrSBe-informant: p = .038; R-squared change = 0.177). Self- and informant-rated FrSBe scores were significantly correlated in the Unemployed group (r = .403; p = .037) but not in the Employed sample (r = .102; p = .717). CONCLUSIONS: These results suggest that behavioral indicators of frontal systems dysfunction are predictive of employment status in individuals with TBI. Future work should aim to test the efficacy of strategies to reduce dysfunctional frontal behaviors as a means to gain and maintain employment. (PsycINFO Database Record

Assessment of depression in epilepsy: the utility of common and disease-specific self-report depression measures.

OBJECTIVES: Depression is common in epilepsy, with rates ranging from 20 to 55% in most samples and reports as high as 70% in patients with intractable epilepsy. However, some contend that depression may be over- and/or under-reported and treated in this population. This may be due to the use of common self-report depression measures that fail to take into account the overlap of disease and depressive symptoms and also the host of side effects associated with antiepileptic medication, which may also be construed as depression. METHODS: The present study examined the utility of common self-report depression measures and those designed specifically for the medically ill, including a proposed new measure, to determine which may be more appropriate for use among people with epilepsy. RESULTS: We found that common self-report depression measures are useful for screening depression in epilepsy, particularly with a raised cutoff for one, with sensitivities ranging from .91 to .96. A measure designed for the medically ill obtained the greatest specificity of .91, suggesting its use as a diagnostic tool with a slightly raised cutoff. The positive likelihood ratio of this latter measure was 8.76 with an overall classification accuracy of 88%. CONCLUSIONS: Assessment of depression in epilepsy can be improved when utilizing self-report measures that better differentiate disease symptoms from neurovegetative symptoms of depression (e.g. fatigue, sleep disturbance). This was demonstrated in the present study. Clinical implications are discussed.

Fronto-striatal network activation leads to less fatigue in multiple sclerosis.

BACKGROUND: The fronto-striatal network has been implicated in both fatigue, a common multiple sclerosis (MS) symptom, and goal attainment, which has been shown to reduce fatigue in healthy individuals. OBJECTIVES: To investigate whether stimulation of the fronto-striatal network through goal attainment (potential monetary gain) leads to fatigue reduction in MS and healthy control (HC) participants. METHODS: In all, 14 healthy and 19 MS participants performed a gambling task during functional magnetic resonance imaging (fMRI). Participants were presented with an opportunity to receive monetary reward during the outcome condition of the task but not during the no outcome condition. Self-reported fatigue measures were obtained after each condition and outside of the scanner. Structural alterations were also examined. RESULTS: A significant decrease in fatigue was observed after the outcome condition compared to the no outcome condition in both groups. Significantly greater activation was observed in the ventral striatum in association with the outcome condition compared to the no outcome condition in both groups. Ventromedial prefrontal cortex showed significantly greater activation during the no outcome condition compared to the outcome condition with greater difference between conditions in the HC group. CONCLUSION: This is the first functional neuroimaging study showing that stimulation of the fronto-striatal network through goal attainment leads to decreased on-task fatigue in MS and healthy participants.