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.