Effects of tobacco and distraction on sensory and slow cortical evoked potentials during task performance.

Sensory and slow cortical evoked potentials (EP) of female smokers were investigated under two conditions in separate sham and real smoking sessions: a non-distraction (ND) condition consisting of a constant fore-period S1-S2, i.e., a single-choice reaction time situation with a tone (S1)/light (S2) key press sequence, and a task distraction (TD) condition identical to ND with the addition of a short-term memory task consisting of four letters presented within the S1-S2 interval with the requirement that subjects repeat after key press to the light. Two individual EP peaks, N1 and P2, were involved in the amplitude analysis of S1 and S2 stimuli; in addition, the amplitude of the slow contingent negative variation (CNV) developing between S1 and S2 was analyzed. Tobacco significantly altered the amplitude of P2 in response to S1 and CNV amplitudes depending on the pre-experimental expired air carbon monoxide (CO) levels of the smokers. Smokers exhibiting low pre-experimental CO levels evidenced tobacco-induced P2 reductions and CNV increments during the ND condition while subjects exhibiting high pre-experimental CO levels displayed similar cortical changes but in the TD conditions. The results are discussed in relation to the role of nicotine and to improved attention and information processing.