SLC18A3 and Alzheimer disease: Furthermore, the AD-MCI group exhibited decreased VAChT-related FC in the right postcentral and precentral gyri and lower α4β2-related FC in the right lingual gyrus and left posterior cingulate cortex, aligning with the early and pervasive involvement of the cholinergic system in Alzheimer’s disease and leading to diminished acetylcholine transmission.