Psychophysiology of Emotion in Parkinsons Disease

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DESCRIPTION (provided by applicant): The overarching goal of the proposed project is to increase understanding of emotional processing in Parkinson's disease. Parkinson's disease is one of the most common neurodegenerative disorders of late life affecting 1-2% of people over the age of 65. It is caused by dopamine depletion with motor, cognitive, and emotional consequences. While advances have been made with respect to motor symptoms, emotional and neuropsychiatric changes (depression, apathy, anxiety) remain highly prevalent and can be the some of the most disturbing, disabling, and complex aspects of the disorder. Two recent studies of emotional responding from our group yielded conflicting results in non-demented Parkinson patients who were psychiatrically normal. One study found blunted emotional reactivity to aversive pictures, as indexed by the startle eye blink response (Bowers et al., 2006), while the other demonstrated normal reactivity as reflected by pupil dilation responses that were larger to emotional than neutral pictures (Dietz et al., 2010). One interpretation of these divergent findings is that pupil dilation and startle eye blink index different components of the emotion processing cascade, namely increased arousal/orienting (pupil) vs. priming of the defense circuitry (startle reflex). In light of these findings, the proposed study is designed to examine, in the same group of Parkinson patients, components of the emotion cascade from emotional arousal, heightened attention and vigilance, to mobilization for goal-directed behavior. To do so, non-demented and non-depressed Parkinson patients and controls will be tested on two tasks, one involving simple picture viewing and the other based on the "predator- prey" task of Low, Lang, Smith, and Bradley (2008). In the latter, cues that signal potential reward/loss or neutrality loom progressively closer until a final "strike-zone" where the participant is required to make a button press, and in target trials either to gain (monetary) reward or avoid a loss. Event-related potentials (LPP, P3), startle eye-blink, and motor reaction times will be used to index arousal/attention, vigilance, and modulated behavior during motivationally relevant and neutral task conditions. Based on known aberrations in neural circuitries affected by dopamine depletion, it is hypothesized that PD patients will have relatively preserved performance on indices of arousal/motivated attention early in the emotion processing cascade but will become increasingly aberrant as the prospect of reward/loss becomes imminent. If supported, findings from this study may suggest a framework for viewing motivational deficits in patients with Parkinson disease, including commonly occurring neuropsychiatric symptoms such as apathy.