Journal Club: Default-mode network connectivity in cognitively unimpaired patients with Parkinson disease.

This Journal Club article looks at a study by Tessitore et al.,(1) who investigated functional connectivity (FC) within the default-mode network (DMN) in cognitively unimpaired patients with Parkinson disease (PD). PD is the second most common neurodegenerative disorder after Alzheimer disease (AD) and is expected to become progressively more prevalent in our aging societies. Thus, its social and economic burden on societies is expected to be even greater in the future.(2) Cognitive impairment is one of the most disabling nonmotor symptoms of PD, further affecting functioning and quality of life, as well as increasing caregivers' burden and health-related costs.(3) When an individual is alert but not actively engaged in cognitive tasks, organized neural activity occurs in a set of brain regions called DMN (figure), which involves the posterior cingulate cortex (PCC), parts of the ventromedial prefrontal cortex, and the precuneus.(4) Interestingly, DMN abnormalities have been linked to cognitive profiles in several neurologic and psychiatric disorders, such as AD, autism, frontotemporal dementia, multiple sclerosis, and vegetative states(5); however, contradictory results have been reported in PD.(1) This study, for the first time, cogently demonstrates decreased FC within the DMN in cognitively unimpaired patients with PD.