Differences between nicotine-abstinent smokers and non-smokers in terms of visuospatial attention and inhibition before and after single-blind nicotine administration

Acetylcholine deficit causes dysfunctional inhibitory control in an aging-dependent manner

Inhibitory control is a key executive function that limits unnecessary thoughts and actions, enabling an organism to appropriately execute goal-driven behaviors. The efficiency of this inhibitory capacity declines with normal aging or in neurodegenerative dementias similar to memory or other cognitive functions. Acetylcholine signaling is crucial for executive function and also diminishes with aging. Acetylcholine's contribution to the aging- or dementia-related decline in inhibitory control, however, remains elusive. We addressed this in Drosophila using a Go/No-Go task that measures inhibition capacity. Here, we report that inhibition capacity declines with aging in wild-type flies, which is mitigated by lessening acetylcholine breakdown and augmented by reducing acetylcholine biosynthesis. We identified the mushroom body (MB) γ neurons as a chief neural site for acetylcholine's contribution to the aging-associated inhibitory control deficit. In addition, we found that the MB output neurons MBON-γ2α'1 having dendrites at the MB γ2 and α'1 lobes and axons projecting to the superior medial protocerebrum and the crepine is critical for sustained movement suppression per se. This study reveals, for the first time, the central role of acetylcholine in the aging-associated loss of inhibitory control and provides a framework for further mechanistic studies.

The role of the SLC6A3 3' UTR VNTR in nicotine effects on cognitive, affective, and motor function

RATIONALE

Nicotine has been widely studied for its pro-dopaminergic effects. However, at the behavioural level, past investigations have yielded heterogeneous results concerning effects on cognitive, affective, and motor outcomes, possibly linked to individual differences at the level of genetics. A candidate polymorphism is the 40-base-pair variable number of tandem repeats polymorphism (rs28363170) in the SLC6A3 gene coding for the dopamine transporter (DAT). The polymorphism has been associated with striatal DAT availability (9R-carriers > 10R-homozygotes), and 9R-carriers have been shown to react more strongly to dopamine agonistic pharmacological challenges than 10R-homozygotes.

OBJECTIVES

In this preregistered study, we hypothesized that 9R-carriers would be more responsive to nicotine due to genotype-related differences in DAT availability and resulting dopamine activity.

METHODS

N=194 non-smokers were grouped according to their genotype (9R-carriers, 10R-homozygotes) and received either 2-mg nicotine or placebo gum in a between-subject design. Spontaneous blink rate (SBR) was obtained as an indirect measure of striatal dopamine activity and smooth pursuit, stop signal, simple choice and affective processing tasks were carried out in randomized order.

RESULTS

Reaction times were decreased under nicotine compared to placebo in the simple choice and stop signal tasks, but nicotine and genotype had no effects on any of the other task outcomes. Conditional process analyses testing the mediating effect of SBR on performance and how this is affected by genotype yielded no significant results.

CONCLUSIONS

Overall, we could not confirm our main hypothesis. Individual differences in nicotine response could not be explained by rs28363170 genotype.

A Randomised Controlled Trial of Inhibitory Control Training for Smoking Cessation: Outcomes, Mediators and Methodological Considerations

Objective: Inhibitory control training (ICT) has shown promise for improving health behaviours, however, less is known about its mediators of effectiveness. The current paper reports whether ICT reduces smoking-related outcomes such as craving and nicotine dependence, increases motivation to quit and whether reductions in smoking or craving are mediated by response inhibition or a devaluation of smoking stimuli.

Method: Adult smokers (minimum 10 cigarettes per day; N = 107, M_age = 46.15 years, 57 female) were randomly allocated to receive 14 days of smoking-specific ICT (named INST; a go/no-go task where participants were trained to not respond to smoking stimuli) or active control training (participants inhibited responding toward neutral stimuli). Participants were followed up to 3-months post-intervention. This trial was preregistered (Australian and New Zealand Clinical Trials Registry ID: ACTRN12617000252314; URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=370204).

Results: There were no significant differences between ICT and active control training groups. Specifically, participants in both groups showed significant reductions in craving, nicotine dependence, motivation and a devaluation (reduced evaluation) of smoking-stimuli up to 3-months follow-up compared to baseline. Inhibition and devaluation of smoking stimuli did not act as mediators. Devaluation of smoking stimuli was an independent predictor of smoking and craving at follow-up.

Conclusion: Inhibitory control training (ICT) was no more effective at reducing smoking-related outcomes compared to the active control group, however, significant improvements in craving, dependence indicators and evaluation of smoking stimuli were observed across both groups. A return to basic experimental research may be required to understand the most effective ICT approach to support smoking cessation.

Inhibitory Performance in Smokers Relative to Nonsmokers When Exposed to Neutral, Smoking- and Money-Related Pictures

INTRODUCTION

Smoking is associated with significant negative health consequences. It has been suggested that deficient inhibitory control may be implicated in (nicotine) addiction, but its exact role has not yet been elucidated. In the current study, our aim was to investigate the role of inhibitory control in relation to nicotine addiction in contexts that differ in terms of reward.

METHODS

Participants filled out questionnaires and performed a go/no-go task with three conditions. In one condition, the stimuli were neutral color squares, and in the reward conditions, these were smoking-related pictures and money-related pictures, respectively. In total, 43 non-abstinent individuals that smoke and 35 individuals that do not smoke were included in the sample.

RESULTS

The main results showed that individuals that smoke, relative to individuals that do not smoke, had reduced inhibitory control in both reward contexts, relative to a neutral context. The reductions in inhibitory control were mirrored by speeded responses.

CONCLUSIONS

Individuals that smoke seem to present with reduced inhibitory control, which is most pronounced in contexts of reward. Consistent with incentive sensitization theory, the reduced inhibitory control may be (at least partly) due to the heightened approach bias to reward-related stimuli as indicated by the speeded responses.

Observational Study of Clinician Attentional Reserves (OSCAR): Acuity-Based Rounds Help Preserve Clinicians' Attention

OBJECTIVES

Team rounding in the ICU can tax clinicians' finite attentional resources. We hypothesized that a novel approach to rounding, where patients are seen in a decreasing order of acuity, would decrease attentional attrition.

DESIGN

Prospective interventional internal-control cohort study in which stop signal task testing was used as a proxy for attentional reserves. Stop signal task is a measure of cognitive control and response inhibition in addition to performance monitoring, all reflective of executive control abilities, and our surrogate for attentional reserves.

SETTING

The ICUs of Vanderbilt University Medical Center (site 1) and the University of Pennsylvania (site 2) from November 2014 to August 2017.

SUBJECTS

Thirty-three clinicians at site 1, and 24 clinicians at site 2.

INTERVENTIONS

Acuity-based rounding, in which clinicians round from highest to lowest acuity as determined by Sequential Organ Failure Assessment score or an equivalent acuity score.

MEASUREMENTS AND MAIN RESULTS

The stop signal task results of ICU staff at two sites were compared for conventional (in room order) versus novel (in decreasing order of acuity) rounding order. At site 1, the difference in stop signal reaction time change between two rounding types was -39.0 ms (95% CI, -50.6 to -27.4 ms; p < 0.001), and at site 2, the performance stop signal reaction time was -15.6 ms (95% CI, -29.1 to -2.1 ms; p = 0.023). These sub-second changes, while small, are significant in the neuroscience domain.

CONCLUSIONS

Rounding in decreasing order of patient acuity mitigated attrition in attentional reserves when compared with the traditional rounding method.

Effects of nicotine and atomoxetine on brain function during response inhibition

The nicotinic acetylcholine receptor (nAChR) agonist nicotine and the noradrenaline transporter inhibitor atomoxetine are widely studied substances due to their propensity to alleviate cognitive deficits in psychiatric and neurological patients and their beneficial effects on some aspects of cognitive functions in healthy individuals. However, despite growing evidence of acetylcholine-noradrenaline interactions, there are only very few direct comparisons of the two substances. Here, we investigated the effects of nicotine and atomoxetine on response inhibition in the stop-signal task and we characterised the neural correlates of these effects using blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) at 3T. Nicotine (7 mg dermal patch) and atomoxetine (60 mg per os) were applied to N = 26 young, healthy adults in a double-blind, placebo-controlled, cross-over, within-subjects design. BOLD images were collected during a stop-signal task that controlled for infrequency of stop trials. There were no drug effects on behavioural performance or subjective state measures. However, there was a pronounced upregulation of activation in bilateral prefrontal and left parietal cortex following nicotine during successful compared to unsuccessful stop trials. The effect of nicotine on BOLD during failed stop trials was correlated across individuals with a measure of trait impulsivity. Atomoxetine, however, had no discernible effects on BOLD. We conclude that nicotine effects on brain function during inhibitory control are most pronounced in individuals with higher levels of impulsivity. This finding is compatible with previous evidence of nicotine effects on stop-signal task performance in highly impulsive individuals and implicates the nAChR in the neural basis of impulsivity.

Nicotine effects on exercise performance and physiological responses in nicotine-naïve individuals: a systematic review

The purpose of this systematic review was to evaluate the effects of smokeless forms of nicotine on physiological responses and exercise performance. Methodology and reporting were based on the PRISMA statement. The intervention was defined as any product containing nicotine that did not require smoking. Searches were conducted across two electronic databases with supplementary approaches utilized. Studies were selected following set inclusion and exclusion criteria and checked by two independent authors. A modified PEDro scale was utilized to rate study quality with studies averaging 9·3/13. Six studies assessed exercise performance with endurance-based parameters reported as significantly improved with nicotine in one study, while anaerobic parameters were unaffected or decreased compared to placebo except in one study which reported enhanced leg extensor torque but no effect on countermovement jump or Wingate anaerobic capacity. Sixteen of 28 studies investigating physiological responses reported that nicotine significantly increased heart rate compared to placebo or control. Blood pressure and blood flow were also reported as significantly increased in multiple studies. While there is strong evidence of nicotine-induced changes in physiological function that would benefit physical performance, beneficial effects have only been reported on leg extensor torque and endurance performance by one study each. Subsequently, there is need for more research with strong methodological quality to definitively evaluate nicotine's potential as an ergogenic aid.

Cognitive Dysfunction, Affective States, and Vulnerability to Nicotine Addiction: A Multifactorial Perspective

Although smoking prevalence has declined in recent years, certain subpopulations continue to smoke at disproportionately high rates and show resistance to cessation treatments. Individuals showing cognitive and affective impairments, including emotional distress and deficits in attention, memory, and inhibitory control, particularly in the context of psychiatric conditions, such as attention-deficit hyperactivity disorder, schizophrenia, and mood disorders, are at higher risk for tobacco addiction. Nicotine has been shown to improve cognitive and emotional processing in some conditions, including during tobacco abstinence. Self-medication of cognitive deficits or negative affect has been proposed to underlie high rates of tobacco smoking among people with psychiatric disorders. However, pre-existing cognitive and mood disorders may also influence the development and maintenance of nicotine dependence, by biasing nicotine-induced alterations in information processing and associative learning, decision-making, and inhibitory control. Here, we discuss the potential forms of contribution of cognitive and affective deficits to nicotine addiction-related processes, by reviewing major clinical and preclinical studies investigating either the procognitive and therapeutic action of nicotine or the putative primary role of cognitive and emotional impairments in addiction-like features.

Small effects of smoking on visual spatiotemporal processing

Nicotine is an important stimulant that is involved in modulating many neuronal processes, including those related to vision. Nicotine is also thought to play a key role in schizophrenia: A genetic variation of the cholinergic nicotine receptor gene, alpha-7 subunit (CHRNA7) has been shown to be associated with stronger backward masking deficits in schizophrenic patients. In this study, we tested visual backward masking in healthy smokers and non-smokers to further understand the effects of nicotine on spatiotemporal vision. In the first study, we tested 48 participants, a group of non-smokers (n = 12) and three groups of regular smokers that were either nicotine deprived (n = 12), non-deprived (n = 12) or deprived but were allowed to smoke a cigarette directly before the start of the experiment (n = 12). Performance was similar across groups, except for some small negative effects in nicotine-deprived participants. In the second study, we compared backward masking performance between regular smokers and non-smokers for older (n = 37, 13 smokers) and younger (n = 67, 21 smokers) adults. Older adults performed generally worse than younger adults but there were no significant differences in performance between smokers and non-smokers. Taken together, these findings indicate that nicotine has no long-term negative effects on visual spatiotemporal processing as determined by visual backward masking.