Acetylcholine is a neurotransmitter and neuromodulator (i.e., a messenger molecule released by nerve cells to signal and regulate other nerve cells). It plays important roles in cognitive function, most notably, in the neural mechanisms of memory. In addition to this memory function, acetylcholine is involved in supporting alertness, attention, and learning. It is also responsible for the neuromuscular junction. It helps skeletal muscle contract and has many health benefits.