Deep Brain Stimulation for Parkinson's Disease: An Investigation of Post-Surgical Self-Regulation and Executive Functioning

OF DISSERTATION DEEP BRAIN STIMULATION FOR PARKINSON’S DISEASE: AN INVESTIGATION OF POST-SURGICAL SELF-REGULATION AND EXECUTIVE FUNCTIONING Parkinson’s Disease (PD) is a common neurodegenerative disorder that attacks the basal ganglia and contributes to a range of motor, cognitive, and behavioral impairments (e.g., tremor, rigidity, and executive dysfunction). This dysfunction may contribute to self-regulatory impairment across several domains, including cognitive skills, thought processes, and emotion. Deep Brain Stimulation (DBS) is a neurosurgical procedure that allows for direct and reversible manipulation of brain activity in patients with PD. The procedure is growing in popularity and is commonly used as an adjunct or in some instances an alternative to dopaminometic medications. Preliminary studies suggest mild executive dysfunction follows DBS but as the literature is in its early stages, there is a need to examine further the range of executive deficits and self-regulatory impairment observed in PD following DBS. In the present study, twenty-seven PD patients post-DBS completed a brief neuropsychological test battery and provided measures of heart rate variability (HRV). Patients also completed questionnaires regarding their ability to self-regulate emotions and thought patterns. Scores were compared to the patient’s pre-surgical performance as well as to a group of healthy older adults. Results suggest DBS leads to significant declines in executive function (EF) and self-regulation (SR). Patients had significantly worse scores on neuropsychological tests of EF (i.e., phonemic fluency, semantic fluency, and working memory) when compared to their preoperative performance. Similarly, DBS patients had significantly worse scores than controls on measures of EF (i.e., verbal fluency, attention, mental flexibility) and verbal memory. With regard to physiological functioning, lower baseline HRV was linked to worse EF but fewer impulsive-compulsive behaviors in DBS patients. Correlations among measures of theoretically similar constructs (i.e., EF and SR) modest and variable, challenging the idea that SR in different domains depends on a common resource.