Objective: Nicotine is an important cholinergic neurotransmitter that has been linked to various cognitive functions. Several studies have observed attentional modulations after nicotine, but the roles played by nicotine and other cholinergic substances in attention remain unclear. The aim of the present pilot study was to identify at which point in the attentional process nicotine exerts its effects.

Participants and Methods: In a double-blind, counterbalanced, crossover design, nine healthy nonsmokers (mean age 26 years) completed two sessions (45 minutes each) after chewing 2 mg nicotine gum or a placebo gum. The experimental paradigm was a letter recognition task with varied stimulus durations terminated by pattern masks. The temporal threshold of conscious perception (t0), visual processing speed (C), storage capacity of visual short-term memory (K), and attentional selectivity (alpha) were measured by use of Bundesen's (1990) Theory of Visual Attention.

Results: As compared with placebo, nicotine caused a significant 40% decrease in the t0-parameter (t[8] = 6.06, p < .001, r = .91) and a 14% decrease in the C-parameter (t[8] = 3.12, p = .01, r = .74). The K-parameter remained unchanged in both conditions. Five subjects showed a marked decrease in selectivity (increase in the alpha-parameter) after nicotine, but this change did not reach significance.

Conclusions: These preliminary data suggest that increased levels of nicotine in the brain (a) advances the point in time at which encoding of information into visual short-term memory is begun, but (b) decreases the rate of encoding and possibly also the attentional selectivity.