Neuroimaging and Neuropsychological Performance in Parkinson's Disease Patients with Normal Cognition: A Systematic Review

Introduction: Cognitive decline is one of Parkinson's disease's (PD) non-motor symptoms that is most frequently observed. Patients with PD exhibit quick cognitive decline in a variety of cognitive domains, particularly in the areas of executive functions, attention, language, memory, and visuospatial abilities. The scope of PD patients with normal cognition (PD-NC) and its relationship to specific regions of the brain as shown by neuroimaging, have not received much attention in the literature. Objective: This review was to summarise the existing literature that explored cognitive performance in PD-NC using different neuroimaging techniques. Methods: A comprehensive search was conducted on PubMed and Web of Science databases. This review focused on papers that investigated neuroimaging and neuropsychological performance in patients with PD. A total of 17 articles have met the criteria. Results: The findings of this review were that executive functions appear to be the most critical cognitive domain to be damaged in PD-NC. Global cognitive ability was found to have insignificant decline overall between PD-NC and healthy controls (HC). Attention and executive functions were associated with the prefrontal cortex. Memory was mainly associated with hippocampal atrophy. Language was associated with cerebrospinal fluid and grey matter. Visuospatial ability was associated with the anterior cingulate cortex. Conclusion:  This review illustrated that PD-NC seemed to experience different cognitive patterns and neuroanatomical changes compared with HC. These results suggested that PD-NC may develop specific cognitive impairments associated with specific brain regions. Therefore, it indicated that PD-NC may need to have specific treatments tailored to their needs.