Double dissociation of working memory and attentional processes in smokers and non-smokers with and without nicotine

Abstract

Nicotine has been shown to affect cortical excitability measured using transcranial magnetic stimulation in smoking and non-smoking subjects in different ways. In tobacco-deprived smokers, administration of nicotine restores compromised cortical facilitation while in non-smokers, it enhances cortical inhibition. As cortical excitability and activity are closely linked to cognitive processes, we aimed to explore whether nicotine-induced physiological alterations in non-smokers and smokers are associated with cognitive changes. Specifically, we assessed the impact of nicotine on working memory performance (n-back letter task) and on attentional processes (Stroop interference test) in healthy smokers and non-smokers. Both tasks have been shown to rely on prefrontal areas, and nicotinic receptors are relevantly involved in prefrontal function. Sixteen smoking and 16 non-smoking subjects participated in the 3-back letter task and 21 smoking and 21 non-smoking subjects in the Stroop test after the respective application of placebo or nicotine patches. The results show that working memory and attentional processes are compromised in nicotine-deprived smokers compared to non-smoking individuals. After administration of nicotine, working memory performance in smokers improved, while non-smoking subjects displayed decreased accuracy with increased number of errors. The effects have been shown to be more apparent for working memory performance than attentional processes. In summary, cognitive functions can be restored by nicotine in deprived smokers, whereas non-smokers do not gain additional benefit. The respective changes are in accordance with related effects of nicotine on cortical excitability in both groups.

Nicotine dependence (trait) and acute nicotinic stimulation (state) modulate attention but not cognitive control: converging fMRI evidence from Go-Nogo and Flanker tasks

“…Rather than a blanket inability to engage cognitive and attentional resources, the deficit appears specific to conditions where only relatively minimal attention is required. The robust effects 14 on attention that we report are in line with literature on attention-enhancing effects of nicotine 14,41 and problems with sustained attention in smokers [42][43][44][45] .…”

“…Some studies report worse cognitive control performance in smokers 30,31,47 , while others did not 33,48,49 . Studies manipulating satiety within-subject similarly reported mixed results for cognitive control tasks 42,44 .…”

Compromised neuroplasticity in cigarette smokers under nicotine withdrawal is restituted by the nicotinic α4β2-receptor partial agonist varenicline

“…Recently, an enhancement of cortical-evoked potentials after prefrontal PAS25 was demonstrated via TMS-EEG 88 . Since cognitive functions that are affected by nicotine abstinence, such as working memory, episodic memory and attention 20 are related to the prefrontal cortex 89–92 and can also be modulated by non-invasive brain stimulation protocols 93, 94 as well as nicotinic agents 1–3 , it would be relevant and feasible to focus the future exploration of nicotine withdrawal-related plasticity shifts directly on prefrontal cortex physiology.…”

“…Apart from disturbed facilitatory plasticity, numerous studies in humans have reported that abstention from nicotine in smokers leads to deficits in working memory and attention 18, 19 , which are partially restituted by re-administration of nicotine or a α 4 β 2 nAChR agonists 20–22 . However, in smoking humans the role of specific nAChRs in the re-establishment of impaired plasticity has not yet been explored.…”

Nicotine modulates human brain plasticity via calcium‐dependent mechanisms

“…; Grundey et al . ) in both animals and humans. Conversely, NIC withdrawal in tobacco smokers is often associated with the deterioration of working and verbal memory and neuroplasticity, whereas NIC re‐administration can restitute those withdrawal‐dependent deficits (Jacobsen et al .…”