In addition to the deposition of Aβ plaques and neurofibrillary tangles, AD progression is related to cholinergic deficiency, as demonstrated by structural alterations in cholinergic synapses, diminished activity of the acetylcholine-synthesizing enzyme choline acetyltransferase (ChAT), loss of specific subtypes of acetylcholine (ACh) receptors, and the death of ACh-generating neurons, which ultimately impair cholinergic neurotransmission [79,80]. Here, CHAT is linked to Alzheimer disease.