Effects of nicotine and incentives on attentional modification of startle in non-smokers
Baschnagel, Joseph Scott
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Nicotine is thought to enhance cognitive processing, particularly attention. Previous studies in the literature give limited support for a positive effect of nicotine on attention and raise the question of whether these effects are due to alleviation of withdrawal or true enhancement of attention. Nicotine has also been shown to increase the effects of incentives on behavior. The current study assessed the effects of nicotine and incentives on attentional processing in a sample of undergraduate non-smokers (n = 67). Non-smokers were chosen in order to rule out withdrawal effects. Automatic and controlled aspects of attention were assessed via attentional modification of short-lead prepulse inhibition (PPI) and long-lead prepulse facilitation (PPF) of the startle eyeblink reflex during an auditory attention task. Participants attended to one of two pitches during an intermixed series of tones, making a button press following the offset of a longer than usual tone (5 vs. 7 s) of the attended pitch. Acoustic startle probes were presented 60, 120, 240, and 4500 ms after onset of 2/3 of the tones and during the intertrial interval. To study the effects of nicotine, participants completed two lab sessions, once while wearing a 7-mg nicotine patch, and once while wearing a placebo patch. To examine incentive effects, half of the participants were offered a monetary reward for task performance and the other half were asked to "try their best." Participants also completed a series of passive PPI trials using discrete prepulses to assess automatic attentional filtering without the influence of an attentional manipulation. Nicotine increased self-reports of nausea and increased heart rate compared to placebo condition. Nicotine increased overall PPI during the tone series, suggesting nicotine improves relatively automatic attentional filtering. Nicotine, incentives, nor their interaction increased attentional modification of PPI or PPF. A regression analysis was employed to test the hypothesis that nicotine's effect would be greatest for those participants who show lower levels of attentional modification. Participants' levels of attentional modification of PPI and PPF during placebo condition were used to predict the amount of change in attentional modification from placebo to nicotine condition. It was evident that nicotine increased attentional modification of both PPI and PPF for participants with low levels of attentional modification during placebo. Surprisingly, nicotine did not increase PPI to passive prepulses. However, levels of PPI to discrete prepulses during placebo condition did predict the effect of nicotine on PPI. Paralleling the tone discrimination task, participants exhibiting lower PPI during the placebo session demonstrated the greatest increase in PPI with nicotine. The results suggest that nicotine can increase automatic attentional filtering and increase focused attentional processes in those participants demonstrating lower levels of these processes in the tone task. These nicotine effects on attention were seen in non-smokers, suggesting that nicotine's effect is more than an amelioration of withdrawal. The significance of the results are discussed in relation to the role of nicotine in increasing automatic and controlled attentional processing, the possible clinical implications, and direction for future research.