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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Neuroscience and Behavior

Year Degree Awarded

2018

Month Degree Awarded

February

First Advisor

Rebecca Ready

Subject Categories

Clinical Psychology | Cognitive Neuroscience

Abstract

A mild traumatic brain injury (mTBI), also known as a concussion, is defined as an injury that results in an alteration of consciousness or mental status. Previous studies have shown mTBI populations experience a number of chronic (> 1 year) symptoms, such as sleep disturbances (e.g., sleep stage alterations), mood alterations (e.g., depressive symptoms), and cognitive alterations (e.g., poor concentration). The three chapters of this dissertation sought to explore these long-term sequelae and the possible interrelations between them. In the first experiment, sleep-dependent memory consolidation of neutral stimuli was probed in a chronic mTBI sample and a control, uninjured sample. I hypothesized memory consolidation would be reduced in the mTBI sample. However, sleep-dependent consolidation was found to be intact in the mTBI sample, despite differences in sleep architecture between groups. Given that risk for mood disorders is elevated following mTBI, in the second experiment, sleep-dependent memory consolidation of emotional images was assessed in groups that were similar to those assessed in Study 1, with the hypothesis that mTBI participants would have reduced consolidation. The mTBI group had reduced sleep-dependent memory consolidation (i.e., memory considation that occurred over a sleep period) but enhanced wake-dependent consolidation (i.e., memory consolidation that occurred over a wake period) of emotional (but not neutral) images. The mTBI group also unexpectedly exhibited a lack of emotion habituation (i.e., emotion desensitization). The third experiment attempted to replicate the latter (unexpected) finding (i.e., reductions in habituation in the mTBI group) while also probing physiological measures of emotion (e.g., heart rate deceleration), which provide an objective measure of emotion. I theorized that reduced habituation might increase the risk for mood disturbances in this population. I was not able to replicate findings of the second experiment, and, on the contrary, found mTBI participants had enhanced emotion habituation In the three experiments, we failed to find expected cognitive and emotional processing deficits in the mTBI samples. In future work, recruiting alternative subsamples of mTBI individuals (e.g., those with Post-concussive syndrome or those with 3 or more mTBIs) could provide insight into which individuals experience negative outcomes in the chronic stages of mTBI.

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