The cholinergic basis of the smoking-induced EEG activation profile.

Acute quantitative electroencephalographic effects of cigarette smoking were examined in 15 smokers within a repeated-measures design which assessed changes in power-spectral estimates following acute pre-treatment with placebo, a dose (20 mg) of mecamylamine, a dose (0.6 mg) of scopolamine and a combined dose of mecamylamine and scopolamine. Compared to sham smoking, the smoking of a single cigarette following placebo pre-treatment reduced absolute and relative power in slow (delta, theta) frequency bands, increased absolute and relative power in alpha and beta frequency bands and accelerated mean frequency. These smoking-induced power changes in slow- and fast-frequency bands were differentially affected by the separate and combined actions of the cholinergic antagonists with treatments involving mecamylamine tending to abolish smoking-induced slow-frequency absolute power reductions and fast-frequency relative power increments. Self-ratings of smoking-induced increases in alertness were altered by mecamylamine and combined treatments while sensory aspects of cigarette smoking were only altered with combined mecamylamine and scopolamine pre-treatment. The results are discussed with respect to brain-behaviour relationships and mechanisms maintaining the smoking habit.