(A) Within the PD group, sensorimotor network (SMN) RSFC strength declines the most for those with higher levels of CSF α-synuclein (i.e., +1 SD above the mean; blue line), while SMN RSFC strength is already reduced and remains relatively stable for those with lower levels (i.e., −1 SD below the mean; red line) of CSF α-synuclein. (B) Dorsal attention network (DAN)-FPCN internetwork strength declined the most among participants with PD with increased cognitive impairment (i.e., +1 SD above the mean; blue line), as measured by increased Clinical Dementia Rating (CDR) sum of boxes scores.