p236fig05.43 The activation of the nucleus basalis of Meynert, and its subsequent release of ACh into deeper layers of neocortex, notably layer 5, is assumed to increase vigilance by reducing afterhyperpolarization (AHP) currents.<BR>||  Vigilance control: mismatch-mediated acetylcholine release (Grossberg and Versace 2008).  Acetylcholine (ACh) regulation by nonspecific thalamic nuclei via nucleus basalis of Meynert reduces AHP in layer 5 and causes a mismatch/reset thereby increasing vigilance. HIGH vigilance ~ sharp code, LOW vigilance ~ coarse code