Effects of nicotine on electroencephalographic (EEG) and behavioural measures of visual working memory in non-smokers during a dual-task paradigm.

Research in smokers has shown that nicotine may have the ability to improve certain aspects of cognitive performance, including working memory and attention, processes which implicate frontal and frontal-parietal brain networks. There is limited research on the cognitive effects of nicotine and their associated neural underpinnings in non-smokers. This study examined the effects of acute nicotine on a working memory task alone or combined with a visual detection task (single- and dual-task conditions) using electroencephalographic (EEG) recordings and behavioural performance measures. Twenty non-smokers (13 females; 7 males) received nicotine gum (6 mg) in a double-blind, randomized, placebo-controlled, repeated measures design. Spectral EEG, together with response speed and accuracy measures, were obtained while participants completed a series of N-Back tasks under single- and dual-task conditions. Nicotine failed to exert any significant effects on performance measures, however, EEG changes were observed, primarily in frontal recordings, which varied with memory load, task condition and hemisphere. These findings, discussed in relation to previous studies in smokers, support the notion that nicotine may modulate central executive systems and contribute to smoking behaviour.

Effects of acute nicotine administration on resting EEG in nonsmokers.

Smoking/nicotine has been shown to increase brain arousal states, yet previous studies have failed to distinguish between absolute improvements due to nicotine versus relief from withdrawal symptoms in smokers. This study examined the electrocortical response to nicotine in a nonsmoking population, in order to negate potential withdrawal symptoms. Twenty right-handed, nonsmoking participants were administered nicotine (6 mg) or placebo gum within a double-blind, repeated-measures design. In each session, EEG was recorded during a 2-min, resting, eyes-open condition. Nicotine administration (vs. placebo) resulted in significantly greater frontal (specifically left-frontal) alpha2 power. Similar to previous findings in smokers. The absence of slow-wave changes following nicotine in nonsmokers suggest that these previous results in smokers may be related to withdrawal state.

Effects of acute nicotine administration on behavioral and neural (EEG) correlates of working memory in non-smokers.

Enhancements in working memory (WM) performance have been previously reported following acute smoking/nicotine. Neuroimaging and behavioral assessments of nicotine's effects on WM have yielded inconsistent findings. Few studies, however, have examined the effects of nicotine on WM-related neural activity in non-smokers. The present study examined the effect of acute nicotine gum administration (6 mg) on electroencephalographic (EEG) activity (alpha(1), alpha(2) and theta bands) and performance on the parametrically manipulated N-back task of WM in 20 non-smoking adults. EEG activity varied with WM load (e.g. alpha(1) decreasing and theta increasing). Performance on the N-back was also load-sensitive, with slower reaction times and decreased accuracy associated with increasing memory load. Neither response speed nor accuracy measures were affected by nicotine but EEG was, with the effects varying by load and brain region. Nicotine-induced increases in alpha(2) and theta were observed under lower (0-, 1-back) memory load conditions Additionally, nicotine significantly reduced signal detection sensitivity values and altered response bias toward being more conservative at all levels of the N-back. Taken together, these findings suggest that while nicotine may boost WM neural processes at lower levels of WM load in non-smokers, it also may activate concurrent behavioral inhibition networks that negate any effects on behavioral performance. Additionally, nicotine appears to have no impact, or perhaps a negative impact, on these processes under more demanding (2-back, 3-back) conditions in non-smokers.