Alpha-Amylase (or α-Amylase) is a digestive enzyme that hydrolyses alpha-1,4 bonds of large polysaccharides such as starch and glycogen, yielding the smaller by-products of glucose and maltose. (1) Alpha amylase is synthesized in the acinar cells of the saliva glands and stored in secretory granules inside the cells. (2)  Its release from the salivary cells is greatly increased in response to taste or chewing motions of the jaw. (3,4,5)  Salivary α-amylase levels are not related to α-amylase levels in blood, which are derived from pancreatic secretion. (1)  In addition to its digestive function, alpha-amylase also plays an important anti-bacterial role in the oral cavity; for this reason it is present in lower levels in non-stimulated saliva between meals. (6,7) Salivary α-amylase exhibits a diurnal rhythm, with a pronounced decrease within 60 minutes after awakening and a steady increase of activity during the course of the day. (8)  Alpha-amylase production in the saliva glands increases in response to psychological and physical stress through interactions with the autonomic nervous system, and it has been found to be a useful as a marker of activity in the autonomic nervous system. (9,10,11)  Salivary alpha-amylase levels have been used as a biomarker of ANS activity in various fields of biobehavioral research. (12,13,14,15)