Author ORCID Identifier

Date Available


Year of Publication


Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation


Arts and Sciences



First Advisor

Dr. Frederick A. Schmitt


Although clinically characterized by motor impairments, Parkinson's disease (PD) often affects cognition early in the disease course. Cognitive changes common in PD include visuospatial abnormalities and prominent executive function (EF) deficits, with 30% of individuals eventually developing Parkinson’s disease dementia (PDD). Mild cognitive impairment (MCI) has been identified as a transitional state between normal cognition and PDD. A large cohort of individuals with PD at the Kentucky Neuroscience Institute have undergone pre-surgical evaluations for deep brain stimulation, although cognitive performance in this cohort has never been probed. Baseline cognitive performance of this cohort from 2017-2020 was examined to characterize the pattern of cognitive functioning in these individuals. Data from 136 patients were available for inclusion, and 110 were available for MCI analyses. Prevalence of MCI was approximately 20%, with highest agreement between MCI criteria and clinician diagnostic impressions using a cut point of 1.5 standard deviations (SD) below normative values. The memory domain was most often impaired for those with MCI (65.5%), whereas the language domain was least often impaired (20.9%). Areas under the curve (AUC) were accordingly weaker for language domain measures (e.g., Boston Naming Test, AUC=.695) relative to domains such as visual memory (e.g., BVMT-R Delay, AUC=.883) and EF (e.g., D-KEFS Trails Switching, AUC=.829). Results support the use of 1.5 SD below normative values as a cut point for identifying MCI in PD and highlight the need for visual memory measures in PD cognitive evaluations. Results also align with the extant findings of impairment in key domains such as EF in PD-MCI. Further longitudinal investigation is needed to elucidate the impact of pre-DBS PD-MCI on post-surgical cognitive outcomes.

Digital Object Identifier (DOI)