Impaired interhemispheric synchrony in Parkinson's disease patients with progressive cognitive impairment

Cognitive decline is a common non-motor symptom of Parkinson's disease (PD), which can occur at any stage of the disease. However, the neural mechanisms of PD cognitive changes remain unclear. It has been reported that hemispheric asymmetry is associated with cognitive impairment. Thus, we aimed to explore the underlying mechanisms of PD subgroups with different degrees of cognitive progression by assessing functional interhemispheric coordination and their relations with cognition. Fifty-four PD patients including 29 stable cognitive performance (sPD) patients, 25 progressive cognitive impairment (pPD) patients, and 18 healthy controls (HC) were recruited in this study. All subjects underwent T1-weighted, resting-state functional magnetic resonance imaging scanning, and neuropsychological evaluations. Voxel-mirrored Homotopic Connectivity (VMHC) and voxel-based morphometry analysis were applied to detect functional interhemispheric coordination. Fisher z transformed VMHC (z-VMHC) value lower in the middle temporal gyrus (MTG), middle occipital gyrus (MOG), and superior temporal gyrus (STG) in the pPD group when compared to the sPD group. However, we did not detect the difference in gray matter volume among the three groups. Furthermore, the z-VMHC value of MTG and MOG was positively correlated with the Montreal Cognitive Assessment (MoCA) score of the follow-up. Therefore, z-VMHC values within the MTG, MOG, and STG appeared to be potential neuroimaging features to distinguish pPD patients from sPD groups. These findings may underlie the neural mechanisms of cognitive performance in PD.