In NDDs, dysregulated ACh balance is crucial: PD motor symptoms are linked to DA‐ACh imbalance and dynamic nAChR changes (early compensation, late reduction); AD cognitive decline relates to basal forebrain cholinergic neuron loss, abnormal mAChR signaling, and nAChR's dual roles (neuroprotection/pathology). This evidence concerns the gene CHRNA4 and Alzheimer disease.