Slow EEG oscillations (delta and theta) depend on the activity level of specific receptors (i.e., muscarinic cholinergic receptors) for the brain chemical acetylcholine; the level of acetylcholine in the cortex and hippocampus is reduced during delta oscillations and elevated during theta activity. Recent findings from the COGA project indicate that the cholinergic receptor genes are involved in theta and delta production (Jones et al. in press) and that these genes also are associated with alcohol dependence. The production of theta and delta rhythms also involves interactions between the GABA and cholinergic neurotransmitter systems; the frequency of theta is controlled by the GABA system, whereas its power is controlled by the cholinergic system (Fellous and Sejnowski 2000; Tiesinga et al. 2001).
