Greater decrease in FC values between bilateral caudate, right middle occipital gyrus, and right middle temporal gyrus in PD-MCI group when compared to HCsFC value for the 3 brain regions significantly lower in APOE4 carriers than non-carriers within PD-MCI groupFC value positively associated with semantic fluency scores in MoCA for only APOE4 carriers within PD-MCI group. The gene discussed is APOE; the disease is Parkinson disease.