Nicotine decreases attentional bias to negative-affect-related Stroop words among smokers.

The present study examined the hypothesis that nicotine is associated with reduced attentional bias to affective and smoking-related stimuli in a modified Stroop task. A total of 56 habitual smokers were each tested on 4 days with 14 mg nicotine patches and placebo patches, counterbalanced, as a within-subjects factor in a double-blind design. A modified Stroop using negative-affect words, smoking words, color words, and neutral words was presented via computer in blocked format. As predicted, nicotine, relative to placebo, was associated with decreased attentional bias to negative words. Nicotine speeded performance during smoking-word and color-word blocks to the same degree as during neutral words and thus appeared to also have a nonspecific performance-enhancing effect. In an exploratory analysis, nicotine-attention effects occurred only in the initial presentation of pairs of blocked word pages. Nicotine also was associated with improved mood. The results are discussed in terms of affect-attention and smoking literatures.

Dopamine receptor (DRD2) genotype-dependent effects of nicotine on attention and distraction during rapid visual information processing.

The effects of nicotine, distractor type, and dopamine type-2 receptor (DRD2) genotype on rapid visual information processing (RVIP) task performance were assessed in habitual smokers. Four RVIP tasks differed in terms of distractor location (central vs. peripheral) and distractor type (numeric vs. emotional). Each participant performed each of the tasks on two different days, once while wearing an active nicotine patch and once while wearing a placebo patch. Overall, the nicotine patch produced more accurate detection of and faster reaction times to target sequences; however, these effects varied with distractor type and genotype. Nicotine speeded reaction time more with left-visual-field (LVF) than right-visual-field (RVF) emotional distractors but speeded reaction time more with RVF than LVF numeric distractors, especially when the distractor digit matched the target sequence in terms of numeric oddness or evenness. Nicotine tended to facilitate performance more in individuals with at least one A1 allele than in homozygous A2A2 individuals, especially with numeric distractors presented to the left hemisphere. Nicotine tended to reduce distraction by negative stimuli more than other types of stimuli. Few gender differences were observed. The overall pattern of results was consistent with the view that nicotine modulates selective attention or subsequent information processing in a manner that depends partly on the emotional versus numeric nature of task distractors, DRD2 genotype, and the brain hemisphere that initially processes the distractors (visual field of distractor).

Effects of nicotine on brain responses to emotional pictures.

Given that nicotine reduces negative affect, one would expect nicotine to have different effects on brain responses to emotionally negative stimuli than it does on responses to emotionally neutral or positive stimuli. However, no studies have assessed this possibility. The present study assessed the effects of nicotine patch versus placebo patch on brain event-related potential (ERP) responses to emotion-inducing negative, positive, and neutral color pictures in 16 smokers in a double-blind, counterbalanced, within-subjects design. The study included four experimental sessions. After overnight smoking deprivation (12 hr or more), active nicotine patches were applied to participants during one of the first two sessions and during one of the last two sessions. Placebo patches were applied during the other two sessions. Nicotine reduced frontal ERP processing voltage negativity (from 144-488 ms poststimulus onset) evoked by viewing emotionally negative pictures to a greater extent than it did when emotionally neutral pictures were viewed, whereas it had no effect on processing negativity evoked by positive pictures. Nicotine also enhanced P390 amplitudes evoked by emotionally negative pictures more than it did when emotionally neutral and positive pictures were viewed. Across picture types, nicotine (relative to placebo) reduced N300 amplitude (more at anterior and dorsal sites) and increased P390 amplitude. Overall, nicotine influenced ERPs to emotionally neutral and positive pictures less than it did to negative pictures.

Effects of transdermal nicotine on lateralized identification and memory interference.

It has been proposed that nicotine may enhance performance on tasks requiring primarily left hemisphere (LH) resources while impairing right hemisphere (RH)-based performance. However, this hypothesis has not been directly tested using a lateralized cognitive task. The effects of transdermal nicotine administration on lateralized consonant identification and memory interference were examined in dependent smokers and never-smokers. In a double-blind placebo-controlled design, smokers (n = 24) and never-smokers (n = 24) were assigned to receive a nicotine or placebo patch. Subjects completed a lateralized letter identification task that required them to identify strings of three consonants presented in the left or right visual field while keeping a word in memory. A distinct right-visual-field (RVF) advantage was observed for consonant identification, but this effect was unaltered by nicotine or smoking status. However, nicotine decreased word memory errors on trials where consonants were presented in the RVF and increased errors on LVF trials. Nicotine may enhance LH-based cognitive performance by increasing LH cognitive resources or by reducing the influence of RVF distracting stimuli. These findings are consistent with a model of the lateralized effects of nicotine on cognitive performance.