The effects of nicotine on the attentional modification of the acoustic startle response in nonsmokers

Rationale and objective: Research on nicotine and attention has mainly utilized samples of deprived smokers and tasks requiring volitional responses, raising the question of whether nicotine improves attention or simply alleviates withdrawal or improves motor speed. This study used the startle eyeblink reflex to assess nicotine effects on auditory attention in nonsmokers. Materials and methods: Sixty-seven healthy young adult nonsmokers completed a tone discrimination task. Acoustic startle probes were presented 60, 120, 240, or 4,500 ms after the onset of two-thirds of the tones and during intertrial intervals. Attention was assessed via (1) short-lead prepulse inhibition (PPI) of startle, a measure of early filtering; (2) long-lead prepulse facilitation (PPF) of startle, a measure of sustained processing; and (3) the modification of PPI and PPF by focused attention. Participants completed two laboratory sessions, once while wearing a 7-mg transdermal nicotine patch and once while wearing a placebo patch. Patches were administered in a double-blind procedure. Results: Nicotine increased overall PPI, η_p² = 0.09. Attention increased long-lead PPF, η_p² = 0.25, but not short-lead PPI. Nicotine did not reliably enhance early or late controlled attentional processing in the sample overall. However, correlational analyses demonstrated that nicotine most improved attentional modification of short-lead PPI among participants with the weakest early attentional processing under placebo conditions. Conclusions: Nicotine enhanced early attentional filtering in general, and the effects of nicotine on early focused attention were dependent upon individual differences in placebo levels of attentional processing. The present data suggest that the effects of nicotine on attention extend beyond the alleviation of withdrawal and simple motor speeding.