Effects of transdermal nicotine on attention in adult non-smokers with and without attentional deficits

Development of cross-species translational paradigms for psychiatric research in the Research Domain Criteria era

The past 30 years of IBNS has included research attempting to treat the cognitive and behavioral deficits observed in people with psychiatric conditions. Early work utilized drugs identified from tests thought to be cognition-relevant, however the high failure rate crossing the translational-species barrier led to focus on developing valid cross-species translational tests. The face, predictive, and neurobiological validities used to assess animal models of psychiatry can be used to validate these tests. Clinical sensitivity is another important aspect however, for if the clinical population targeted for treatment does not exhibit task deficits, then why develop treatments? This review covers some work validating cross-species translational tests and suggests future directions. Also covered is the contribution IBNS made to fostering such research and my role in IBNS, making it more available to all including fostering mentor/mentee programs plus spearheading diversity and inclusivity initiatives. All science needs support and IBNS has supported research recreating the behavioral abnormalities that define psychiatric conditions with the aim to improve the lives of people with such conditions.

Xanomeline restores endogenous nicotinic acetylcholine receptor signaling in mouse prefrontal cortex

Cholinergic synapses in prefrontal cortex are vital for attention, but this modulatory system undergoes substantial pre- and post-synaptic alterations during adulthood. To examine the integrated impact of these changes, we optophysiologically probe cholinergic synapses ex vivo, revealing a clear decline in neurotransmission in middle adulthood. Pharmacological dissection of synaptic components reveals a selective reduction in postsynaptic nicotinic receptor currents. Other components of cholinergic synapses appear stable, by contrast, including acetylcholine autoinhibition, metabolism, and excitation of postsynaptic muscarinic receptors. Pursuing strategies to strengthen cholinergic neurotransmission, we find that positive allosteric modulation of nicotinic receptors with NS9283 is effective in young adults but wanes with age. To boost nicotinic receptor availability, we harness the second messenger pathways of the preserved excitatory muscarinic receptors with xanomeline. This muscarinic agonist and cognitive-enhancer restores nicotinic signaling in older mice significantly, in a muscarinic- and PKC-dependent manner. The rescued nicotinic component regains youthful sensitivity to allosteric enhancement: treatment with xanomeline and NS9283 restores cholinergic synapses in older mice to the strength, speed, and receptor mechanism of young adults. Our results reveal a new and efficient strategy to rescue age-related nicotinic signaling deficits, demonstrating a novel pathway for xanomeline to restore cognitively-essential endogenous cholinergic neurotransmission.

Translational cognitive systems: focus on attention

Cognitive dysfunction, particularly attentional impairment, is a core feature of many psychiatric disorders, yet is inadequately addressed by current treatments. Development of targeted therapeutics for the remediation of attentional deficits requires knowledge of underlying neurocircuit, cellular, and molecular mechanisms that cannot be directly assayed in the clinic. This level of detail can only be acquired by testing animals in cross-species translatable attentional paradigms, in combination with preclinical neuroscience techniques. The 5-choice continuous performance test (5C-CPT) and rodent continuous performance test (rCPT) represent the current state of the art of preclinical assessment of the most commonly studied subtype of attention: sustained attention, or vigilance. These tasks present animals with continuous streams of target stimuli to which they must respond (attention), in addition to non-target stimuli from which they must withhold responses (behavioral inhibition). The 5C-CPT and rCPT utilize the same measures as gold-standard clinical continuous performance tests and predict clinical efficacy of known pro-attentional drugs. They also engage common brain regions across species, although efforts to definitively establish neurophysiological construct validity are ongoing. The validity of these tasks as translational vigilance assessments enables their use in characterizing the neuropathology underlying attentional deficits of animal models of psychiatric disease, and in determining therapeutic potential of drugs ahead of clinical testing. Here, we briefly review the development and validation of such tests of attentional functioning, as well as the data they have generated pertaining to inattention, disinhibition, and impulsivity in psychiatric disorders.

A phenome-wide association study of polygenic scores for attention deficit hyperactivity disorder across two genetic ancestries in electronic health record data

Testing the association between genetic scores for Attention Deficit Hyperactivity Disorder (ADHD) and health conditions, can help us better understand its complex etiology. Electronic health records linked to genetic data provide an opportunity to test whether genetic scores for ADHD correlate with ADHD and additional health outcomes in a health care context across different age groups. We generated polygenic scores (ADHD-PGS) trained on summary statistics from the latest genome-wide association study of ADHD (N = 55,374) and applied them to genome-wide data from 12,383 unrelated individuals of African-American ancestry and 66,378 unrelated individuals of European ancestry from the Vanderbilt Biobank. Overall, only Tobacco use disorder (TUD) was associated with ADHD-PGS in the African-American ancestry group (Odds ratio [95% confidence intervals] = 1.23[1.16-1.31], p = 9.3 × 10-09 ). Eighty-six phenotypes were associated with ADHD-PGS in the European ancestry individuals, including ADHD (OR[95%CIs] = 1.22[1.16-1.29], p = 3.6 × 10-10 ), and TUD (OR[95%CIs] = 1.22[1.19-1.25], p = 2.8 × 10-46 ). We then stratified outcomes by age (ages 0-11, 12-18, 19-25, 26-40, 41-60, and 61-100). Our results suggest that ADHD polygenic scores are associated with ADHD diagnoses early in life and with an increasing number of health conditions throughout the lifespan (even in the absence of ADHD diagnosis). This study reinforces the utility of applying trait-specific PGSs to biobank data, and performing exploratory sensitivity analyses, to probe relationships among clinical conditions.

Impact of Nicotine on Cognition in Patients With Schizophrenia: A Narrative Review

Nicotine is the psychoactive component given tobacco has several main components and acts as an agonist for nicotinic acetylcholine receptors (nAChRs) in the nervous system. Although the ligand-gated cation channels known as nAChRs are found throughout the nervous system and body, this review focuses on neuronal nAChRs. Individuals with psychiatric diseases such as schizophrenia, comorbid substance use disorders, attention-deficit hyperactivity disorder, major depression, and bipolar disorder have increased rates of smoking. These psychiatric disorders are associated with various cognitive deficits, including working memory, deficits in attention, and response inhibition functions. The cognitive-enhancing effects of nicotine may be particularly relevant predictors of smoking initiation and continuation in this comorbid population. Individuals with schizophrenia make up a significant proportion of smokers. Literature suggests that patients smoke to alleviate cognitive deficiencies due to the stimulating effects of nicotine. This narrative review examines the role of nicotine on cognition in schizophrenia.

Preclinical Evaluation of Attention and Impulsivity Relevant to Determining ADHD Mechanisms and Treatments

People with Attention-Deficit Hyperactivity Disorder (ADHD) exhibit inattention, hyperactivity, and/or impulsivity. Symptoms of ADHD emerge in childhood and can continue throughout adulthood. Clinical assessments to diagnose ADHD can include administration of continuous performance tests (CPTs). CPTs provide an objective measure of inattention, requiring individuals to respond to targets (attention), and inhibit response to non-targets (impulsivity). When investigating the mechanisms of, and novel treatments for, ADHD it is important to measure such behavioral domains (attention and impulsivity). Some well-established preclinical tasks purport to assess attention in rodents but, unlike CPTs, do not require non-target inhibition, limiting their ADHD-relevance.Recently developed tasks recreate CPTs for rodents. The 5-Choice CPT (5C-CPT) contains non-target stimuli, enabling use of signal detection theory to evaluate performance, consistent with CPTs. The 5C-CPT has been adapted for use in humans, enabling direct cross-species comparisons of performance. A newer task, the rodent CPT (rCPT), is a touchscreen-based analog of CPTs, utilizing symbols instead of a simple stimulus array. Currently, the rCPT may be more akin to a go/no-go task, equally presenting targets/non-targets, although numerous variants exist - a strength. The 5C-CPT and rCPT emulate human CPTs and provide the most up-to-date information on ADHD-relevant studies for understanding attention/impulsivity.

Association of Attention-Deficit/Hyperactivity Disorder With E-Cigarette Use

INTRODUCTION

E-cigarette use in young people has emerged as a public health concern in the U.S. Previous studies have shown that individuals with attention-deficit/hyperactivity disorder are more likely to use conventional cigarettes. However, little is known about their use of E-cigarettes. This study examines the association of attention-deficit/hyperactivity disorder with E-cigarette and other tobacco product use among undergraduate and graduate students in the U.S.

METHODS

This study included data from 195,443 U.S. undergraduate and graduate students aged 18-39 years who participated in the National College Health Assessment surveys from spring 2017 to fall 2018. History of attention-deficit/hyperactivity disorder diagnosis and current use of conventional cigarettes, E-cigarettes, and other tobacco products were ascertained by questionnaires. Logistic regression models estimated the ORs and 99% CIs of use of conventional cigarettes, E-cigarettes, and other tobacco products according to attention-deficit/hyperactivity disorder history.

RESULTS

Among the 195,443 students, 16,800 (8.35%) were current conventional cigarette users and 15,863 (7.89%) were current E-cigarette users; 16,283 (8.10%) had a history of attention-deficit/hyperactivity disorder diagnosis. After adjustment for demographics, socioeconomics, lifestyle factors, BMI, anxiety, and depression, the OR of E-cigarette use among participants with attention-deficit/hyperactivity disorder, compared with those without attention-deficit/hyperactivity disorder, was 1.72 (99% CI=1.60, 1.85), which was comparable to the magnitude of associations for other tobacco products.

CONCLUSIONS

Among U.S. undergraduate and graduate students, there is a significant association between attention-deficit/hyperactivity disorder diagnosis and current use of E-cigarettes. Health consequences of E-cigarette use among individuals with an attention-deficit/hyperactivity disorder diagnosis warrant further investigation.

Acute administration of nicotine does not enhance cognitive functions

Chronic smokers often claim that smoking improves their cognitive abilities, such as concentration. However, scientific evidence to support this claim is scarce. Previous studies gave inconclusive results, and some of them had significant methodological flaws. Therefore, the aim of this study was to test whether smoking a single cigarette affects performance across several cognitive domains. It included a group of 22 occasional smokers aged 19-29 years. Attention, working memory, and visuospatial reasoning were assessed using a within-subjects design with a control setting. There were two separate testing sessions two days apart. Half the group started with experimental and the other half with control setting. In the experimental setting, the participants completed the first block of tasks, smoked one cigarette (with a nicotine yield of 0.5 mg), and then completed the second block of tasks. In the control setting, the procedure was the same, except that the participants had a glass of water instead of a cigarette. Repeated measures ANOVA showed no significant effects of cigarette smoking on either reaction time rates or accuracy on any of the three cognitive domains. These results suggest that, at least among young, occasional smokers, smoking does not affect cognition and the claims of its improvement are probably a result of some sort of cognitive bias.

The impact of nicotine dose and instructed dose on smokers' implicit attitudes to smoking cues: An ERP study

It is unclear whether nicotine and perceived nicotine exposure can influence automatic evaluations of cigarette stimuli. In the present study, we investigated the effects of nicotine dose and instructed dose on motivational responses to smoking cues. Forty overnight nicotine-deprived smokers completed an Implicit Association Test (IAT) at each of the four laboratory sessions in a balanced-placebo design that crossed nicotine dose (Given-NIC [given nicotine] vs. Given-DENIC [given denicotinized]) with instructed dose expectancy (Told-NIC [told-nicotine] vs. Told-DENIC. [told-denicotinized]). We measured participants' behavioral performance, including reaction time (RT) and accuracy rate, and the early posterior negativity (EPN) component using the event-related potential (ERP) technique to the target pictures. During congruent trials when the categorization condition was smoking or unpleasant, smokers had greater classification accuracy, shorter RT latency, and greater EPN amplitudes compared to the incongruent trials when the categorization condition was smoking or pleasant. The Given-NIC condition was associated with increased classification accuracy, longer RT latency, and decreased EPN amplitudes compared to the Given-DENIC condition. Similarly, the Told-NIC condition was associated with increased accuracy and decreased EPN amplitudes compared to the Told-DENIC condition, but with shorter RT latency. Cigarette-related pictures produced greater EPN amplitudes than neutral pictures. Both behavioral and ERP results suggest that smokers have negative implicit attitudes toward smoking. While both nicotine dose and expected dose facilitated stimulus categorization, there was no evidence that either factor altered smokers' negative attitudes toward smoking cues. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

NAChR α4β2 Subtype and their Relation with Nicotine Addiction, Cognition, Depression and Hyperactivity Disorder

BACKGROUND

Neuronal α4β2 nAChRs are receptors involved in the role of neurotransmitters regulation and release, and this ionic channel participates in biological process of memory, learning and attention. This work aims to review the structure and functioning of the α4β2 nAChR emphasizing its role in the treatment of associated diseases like nicotine addiction and underlying pathologies such as cognition, depression and attention-deficit hyperactivity disorder.

METHODS

The authors realized extensive bibliographic research using the descriptors "Nicotine Receptor α4β2" and "cognition", "depression", "attention-deficit hyperactivity disorder", besides cross-references of the selected articles and after analysis of references in the specific literature.

RESULTS

As results, it was that found 179 relevant articles presenting the main molecules with affinity to nAChR α4β2 related to the cited diseases. The α4β2 nAChR subtype is a remarkable therapeutic target since this is the most abundant receptor in the central nervous system.

CONCLUSION

In summary, this review presents perspectives on the pharmacology and therapeutic targeting of α4β2 nAChRs for the treatment of cognition and diseases like nicotine dependence, depression and attention-deficit hyperactivity disorder.

Impact of Substance Use Disorder Pharmacotherapy on Executive Function: A Narrative Review

Substance use disorders are chronic, relapsing, and harmful conditions characterized by executive dysfunction. While there are currently no approved pharmacotherapy options for stimulant and cannabis use disorders, there are several evidence-based options available to help reduce symptoms during detoxification and aid long-term cessation for those with tobacco, alcohol and opioid use disorders. While these medication options have shown clinical efficacy, less is known regarding their potential to enhance executive function. This narrative review aims to provide a brief overview of research that has investigated whether commonly used pharmacotherapies for these substance use disorders (nicotine, bupropion, varenicline, disulfiram, acamprosate, nalmefene, naltrexone, methadone, buprenorphine, and lofexidine) effect three core executive function components (working memory, inhibitory control and cognitive flexibility). While pharmacotherapy-induced enhancement of executive function may improve cessation outcomes in dependent populations, there are limited and inconsistent findings regarding the effects of these medications on executive function. We discuss possible reasons for the mixed findings and suggest some future avenues of work that may enhance the understanding of addiction pharmacotherapy and cognitive training interventions and lead to improved patient outcomes.

Nicotine increases sleep spindle activity

Studies have shown that both nicotine and sleep spindles are associated with enhanced memorisation. Further, a few recent studies have shown how cholinergic input through nicotinic and muscarinic receptors can trigger or modulate sleep processes in general, and sleep spindles in particular. To better understand the interaction between nicotine and sleep spindles, we compared in a single blind randomised study the characteristics of sleep spindles in 10 healthy participants recorded for 2 nights, one with a nicotine patch and one with a sham patch. We investigated differences in sleep spindle duration, amplitude, intra-spindle oscillation frequency and density (i.e. spindles per min). We found that under nicotine, spindles are more numerous (average increase: 0.057 spindles per min; 95% confidence interval: [0.025-0.089]; p = .0004), have higher amplitude (average amplification: 0.260 μV; confidence interval: [0.119-0.402]; p = .0032) and last longer (average lengthening: 0.025 s; confidence interval: [0.017-0.032]; p = 2.7e-11). These results suggest that nicotine can increase spindle activity by acting on nicotinic acetylcholine receptors, and offer an attractive hypothesis for common mechanisms that may support memorisation improvements previously reported to be associated with nicotine and sleep spindles.

Nicotine improves probabilistic reward learning in wildtype but not alpha7 nAChR null mutants, yet alpha7 nAChR agonists do not improve probabilistic learning

Cognitive impairments, e.g., reward learning, are present in various psychiatric disorders and warrant treatment. Improving reward-related learning could synergistically enhance psychosocial treatments and cognition generally. A critical first step is to understand the mechanisms underlying reward learning. The dopamine system has been implicated in such learning, but less known is how indirect activation of this system may affect reward learning. We determined the role of alpha7 nicotinic acetylcholine receptors (nAChR) on a probabilistic reversal learning task (PRLT) in mice that includes reward and punishment. Male alpha7 knockout (KO), heterozygous (HT), and wildtype (WT) littermate mice (n = 84) were treated with vehicle, 0.03, or 0.3 mg/kg nicotine. Two cohorts of C57BL/6NJ male mice were treated with various alpha7 nAChR ligands, including the full agonists PNU282877 and AR-R-17779, the positive allosteric modulator CCMI, the partial agonist SSR180711, and the antagonist methyllycaconitine. All mice were then tested in the PRLT. Nicotine (0.3 mg/kg) significantly improved initial reward learning in alpha7 WT and HT mice but did not improve learning in KO mice, suggesting an involvement of the alpha7 nAChR in the pro-learning effects of nicotine. Neither alpha7 nAChR treatments (PNU282987, AR-R-17779, CCMI, SSR180711, nor methyllycaconitine) affected mouse PRLT performance however. Nicotine improved reward learning via a mechanism that may include alpha7 nAChRs. This improvement unlikely relied solely on alpha7 nAChRs however, since no alpha7 nAChR ligand improved reward learning in normal mice. Future assessments of the effects of other nAChR subtypes on reward learning are needed.

Transdermal Nicotine for the Treatment of Mood and Cognitive Symptoms in Nonsmokers With Late-Life Depression

OBJECTIVE

Late-life depression (LLD) is characterized by poor antidepressant response and cognitive dysfunction. This study examined whether transdermal nicotine benefits mood symptoms and cognitive performance in LLD.

METHODS

In a 12-week open-label outpatient study conducted between November 2016 and August 2017, transdermal nicotine was given to 15 nonsmoking older adults (≥ 60 years of age). Eligible participants met DSM-IV-TR criteria for major depressive disorder with ≥ 15 on the Montgomery-Asberg Depression Rating scale (MADRS) and endorsed subjective cognitive impairment. Transdermal nicotine patches were applied daily and titrated in a rigid dose escalation strategy to a maximum dose of 21.0 mg/d, allowing dose reductions for tolerability. The primary mood outcome was MADRS change measured every 3 weeks, with response defined as ≥ 50% improvement from baseline and remission as MADRS score ≤ 8. The primary cognitive outcome was the Conners Continuous Performance Test (CPT), a test of attention.

RESULTS

Robust rates of response (86.7%; 13/15 subjects) and remission (53.3%; 8/15 subjects) were observed. There was a significant decrease in MADRS scores over the study (β = -1.51, P < .001), with improvement seen as early as 3 weeks (Bonferroni-adjusted P value = .004). We also observed improvement in apathy and rumination. We did not observe improvement on the CPT but did observe improvement in subjective cognitive performance and signals of potential drug effects on secondary cognitive measures of working memory, episodic memory, and self-referential emotional processing. Overall, transdermal nicotine was well tolerated, although 6 participants could not reach the maximum targeted dose.

CONCLUSIONS

Nicotine may be a promising therapy for depressed mood and cognitive performance in LLD. A definitive placebo-controlled trial and establishment of longer-term safety are necessary before clinical usage.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02816138​.

Cognitive effects of labeled addictolytic medications

INTRODUCTION

Alcohol, tobacco, and illegal drug usage is pervasive throughout the world, and abuse of these substances is a major contributor to the global disease burden. Many pharmacotherapies have been developed over the last 50years to target addictive disorders. While the efficacy of these pharmacotherapies is largely recognized, their cognitive impact is less known. However, all substance abuse disorders are known to promote cognitive disorders like executive dysfunction and memory impairment. These impairments are critical for the maintenance of addictive behaviors and impede cognitive behavioral therapies that are regularly administered in association with pharmacotherapies. It is also unknown if addictolytic medications have an impact on preexisting cognitive disorders, and if this impact is modulated by the indication of prescription, i.e. abstinence, reduction or substitution, or by the specific action of the medication.

METHOD

We reviewed the cognitive effects of labeled medications for tobacco addiction (varenicline, bupropion, nicotine patch and nicotine gums), alcohol addiction (naltrexone, nalmefene, baclofen, disulfiram, sodium oxybate, acamprosate), and opioid addiction (methadone, buprenorphine) in human studies. Studies were selected following MOOSE guidelines for systematic reviews of observational studies, using the keywords [Cognition] and [Cognitive disorders] and [treatment] for each medication.

RESULTS

971 articles were screened and 77 studies met the inclusion criteria and were reported in this review (for alcohol abuse, n=21, for tobacco n=22, for opioid n=34. However, very few comparative clinical trials have explored the chronic effects of addictolytic medications on cognition in addictive behaviors, and there are no clinical trials on the cognitive impact of nalmefene in patients suffering from alcohol use disorders.

DISCUSSION

Although some medications seem to enhance cognition in patients suffering from cognitive disorders, others could promote cognitive impairments, and our work highlights a lack of literature on this subject. In conclusion, more comparative clinical trials are needed to better understand the cognitive impact of addictolytic medications.

Cognitive Effects of Nicotine: Recent Progress

BACKGROUND

Cigarette smoking is the main cause of preventable death in developed countries. While the direct positive behavioral reinforcing effect of nicotine has historically been considered the primary mechanism driving the development of TUD, accumulating contemporary research suggests that the cognitive-enhancing effects of nicotine may also significantly contribute to the initiation and maintenance of TUD, especially in individuals with pre-existing cognitive deficits.

METHODS

We provide a selective overview of recent advances in understanding nicotine's effects on cognitive function, a discussion of the role of cognitive function in vulnerability to TUD, followed by an overview of the neurobiological mechanisms underlying the cognitive effects of nicotine.

RESULTS

Preclinical models and human studies have demonstrated that nicotine has cognitiveenhancing effects. Attention, working memory, fine motor skills and episodic memory functions are particularly sensitive to nicotine's effects. Recent studies have demonstrated that the α4, β2, and α7 subunits of the nicotinic acetylcholine receptor (nAChR) participate in the cognitive-enhancing effects of nicotine. Imaging studies have been instrumental in identifying brain regions where nicotine is active, and research on the dynamics of large-scale networks after activation by, or withdrawal from, nicotine hold promise for improved understanding of the complex actions of nicotine on human cognition.

CONCLUSION

Because poor cognitive performance at baseline predicts relapse among smokers who are attempting to quit smoking, studies examining the potential efficacy of cognitive-enhancement as strategy for the treatment of TUD may lead to the development of more efficacious interventions.

Nicotine and networks: Potential for enhancement of mood and cognition in late-life depression

Late-life depression is characterized by both lower mood and poor cognitive performance, symptoms that often do not fully respond to current antidepressant medications. Nicotinic acetylcholine receptor (nAChR) agonists such as nicotine may serve as a novel therapeutic approach for this population. Both preclinical and preliminary clinical studies suggest that nAChR agonists can improve depressive behavior in animal models and improve mood in depressed individuals. Substantial literature also supports that nAChR agonists benefit cognitive performance, particularly in older populations. These potential benefits may be mediated by the effects of nAChR stimulation on neural network function and connectivity. Functional neuroimaging studies detail effects of nAChR agonists on the default mode network, central-executive network, and salience network that may oppose or reverse network changes seen in depression. We propose that, given the existent literature and the clinical presentation of late-life depression, nicotine or other nAChR agonists may have unique therapeutic benefits in this population and that clinical trials examining nicotine effects on mood, cognition, and network dynamics in late-life depression are justified.

Partial agonism at the α7 nicotinic acetylcholine receptor improves attention, impulsive action and vigilance in low attentive rats

Inattention is a disabling symptom in conditions such as schizophrenia and attention deficit/hyperactivity disorder. Nicotine can improve attention and vigilance, but is unsuitable for clinical use due to abuse liability. Genetic knockout of the α7 nicotinic acetylcholine receptor (nAChR) induces attention deficits therefore selective agonism may improve attention, without the abuse liability associated with nicotine. The α7 nAChR partial agonist encenicline (formerly EVP-6124) enhances memory in rodents and humans. Here we investigate, for the first time, efficacy of encenicline to improve attention and vigilance in animals behaviourally grouped for low attentive traits in the 5 choice-continuous performance task (5C-CPT). Female Lister Hooded rats were trained to perform the 5C-CPT with a variable stimulus duration (SD). Animals were then grouped based on performance into upper and lower quartiles of d' (vigilance) and accuracy (selective attention), producing high-attentive (HA) and low-attentive (LA) groups. LA animals showed an increase in selective attention and vigilance at 0.3mg/kg encenicline, a reduction in impulsive action (probability of false alarms) and increase in vigilance following 1mg/kg at 0.75sSD. At 1mg/kg, HA animals had reduced selective attention at 0.75sSD and reduced vigilance at 0.75 and 1.25sSD. Improvement of attention, vigilance and impulsive action in LA animals demonstrates that encenicline has pro-attentive properties dependent on baseline levels of performance. Our work suggests that α7 nAChR partial agonism may improve attention particularly in conditions with low attention.

Moderation of nicotine effects on covert orienting of attention tasks by poor placebo performance and cue validity

INTRODUCTION AND RATIONALE

Given baseline-dependent effects of nicotine on other forms of attention, there is reason to believe that inconsistent findings for the effects of nicotine on attentional orienting may be partly due to individual differences in baseline (abstinence state) functioning. Individuals with low baseline attention may benefit more from nicotine replacement.

METHOD

The effects of nicotine as a function of baseline performance (bottom, middle, and top third of mean reaction times during placebo) were assessed in 52 habitual abstinent smokers (26 females/26 males) utilizing an arrow-cued covert orienting of attention task.

RESULTS

Compared to a placebo patch, a 14mg nicotine patch produced faster overall reaction times (RTs). In addition, individuals with slower RTs during the placebo condition benefitted more from nicotine on cued trials than did those who had shorter (faster) RTs during placebo. Nicotine also enhanced the validity effect (shorter RTs to validly vs. invalidly cued targets), but this nicotine benefit did not differ as a function of overall placebo-baseline performance.

CONCLUSIONS

These findings support the view that nicotine enhances cued spatial attentional orienting in individuals who have slower RTs during placebo (nicotine-free) conditions; however, baseline-dependent effects may not generalize to all aspects of spatial attention. These findings are consistent with findings indicating that nicotine's effects vary as a function of task parameters rather than simple RT speeding or cognitive enhancement.

Nicotine-dopamine-transporter interactions during reward-based decision making

Our everyday-life comprises a multitude of decisions that we take whilst trying to maximize advantageous outcomes, limit risks and update current needs. The cognitive processes that guide decision making as well as the brain circuits they are based on are only poorly understood. Numerous studies point to a potential role of dopamine and nicotine in decision making but less is known about their interactions. Here, 26 healthy male subjects performed the Iowa Gambling Task (IGT) in two sessions following the administration of either nicotine or placebo. Striatal dopamine transporter (DAT) binding was measured by single-photon emission computed tomography (SPECT). Results indicate that lower DAT levels were associated with better performance in the IGT (p=0.0004). Cognitive modelling analysis using the prospect valence learning (PVL) model indicated that low DAT subjects' performance deteriorated following nicotine administration as indicated by an increased learning rate and a decreased response consistency. Our results shed light on the neurochemistry underlying reward-based decision making in humans by demonstrating a significant interaction between nicotine and the DAT. The observed interaction is consistent with the hypothesized associations between DAT expression and extracellular dopamine levels, suggestive of an inverted U-shape relationship between baseline dopamine and magnitude in response to a pro-dopaminergic compound. Our findings are of particular interest in the context of psychiatric disorders where aberrant decision making represents a part of the core symptomatology, such as addiction, schizophrenia or depression.

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.

Neuronal effects of nicotine during auditory selective attention

RATIONALE

Although the attention-enhancing effects of nicotine have been behaviorally and neurophysiologically well-documented, its localized functional effects during selective attention are poorly understood.

OBJECTIVES

In this study, we examined the neuronal effects of nicotine during auditory selective attention in healthy human nonsmokers. We hypothesized to observe significant effects of nicotine in attention-associated brain areas, driven by nicotine-induced increases in activity as a function of increasing task demands.

METHODS

A single-blind, prospective, randomized crossover design was used to examine neuronal response associated with a go/no-go task after 7 mg nicotine or placebo patch administration in 20 individuals who underwent functional magnetic resonance imaging at 3T. The task design included two levels of difficulty (ordered vs. random stimuli) and two levels of auditory distraction (silence vs. noise).

RESULTS

Significant treatment × difficulty × distraction interaction effects on neuronal response were observed in the hippocampus, ventral parietal cortex, and anterior cingulate. In contrast to our hypothesis, U and inverted U-shaped dependencies were observed between the effects of nicotine on response and task demands, depending on the brain area.

CONCLUSIONS

These results suggest that nicotine may differentially affect neuronal response depending on task conditions. These results have important theoretical implications for understanding how cholinergic tone may influence the neurobiology of selective attention.

Nicotine reduces distraction under low perceptual load

RATIONALE

Several studies provide evidence that nicotine alleviates the detrimental effects of distracting sensory stimuli. It is been suggested that nicotine may either act as a stimulus filter that prevents irrelevant stimuli entering awareness or by enhancing the attentional focus to relevant stimuli via a boost in processing capacity.

OBJECTIVES

To differentiate between these two accounts, we administered nicotine to healthy non-smokers and investigated distractor interference in a visual search task with low and high perceptual load to tax processing capacity.

METHODS

Thirty healthy non-smokers received either 7 mg transdermal nicotine or a matched placebo in a double blind within subject design 1 h prior to performing the visual search task with different fixation distractors.

RESULTS

Nicotine reduced interference of incongruent distractors, but only under low-load conditions, where distractor effects were large. No effects of nicotine were observed under high-load conditions. Highly distractible subjects showed the largest effects of nicotine.

CONCLUSIONS

The findings suggest that nicotine acts primarily as a stimulus filter that prevents irrelevant stimuli from entering awareness in situations of high distractor interference.

Nicotinic receptors and attention

Facilitation of different attentional functions by nicotinic acetylcholine receptor (nAChR) agonists may be of therapeutic potential in disease conditions such as Alzheimer's disease or schizophrenia. For this reason, the neuronal mechanisms underlying these effects have been the focus of research in humans and in preclinical models. Attention-enhancing effects of the nonselective nAChR agonist nicotine can be observed in human nonsmokers and in laboratory animals, suggesting that benefits go beyond a reversal of withdrawal deficits in smokers. The ultimate aim is to develop compounds acting with greater selectivity than nicotine at a subset of nAChRs, with an effects profile narrowly matching the targeted cognitive deficits and minimizing unwanted effects. To date, compounds tested clinically target the nAChR subtypes most abundant in the brain. To help pinpoint more selectively expressed subtypes critical for attention, studies have aimed at identifying the secondary neurotransmitter systems whose stimulation mediates the attention-enhancing properties of nicotine. Evidence indicates that noradrenaline and glutamate, but not dopamine release, are critical mediators. Thus, attention-enhancing nAChR agents could spare the system central to nicotine dependence. Neuroimaging studies suggest that nAChR agonists act on a variety of brain systems by enhancing activation, reducing activation, and enhancing deactivation by attention tasks. This supports the notion that effects on different attentional functions may be mediated by distinct central mechanisms, consistent with the fact that nAChRs interact with a multitude of brain sites and neurotransmitter systems. The challenge will be to achieve the optimal tone at the right subset of nAChR subtypes to modulate specific attentional functions, employing not just direct agonist properties, but also positive allosteric modulation and low-dose antagonism.

Targeting the nicotinic cholinergic system to treat attention-deficit/hyperactivity disorder: rationale and progress to date

Attention-deficit/hyperactivity disorder (ADHD) is a common chronic neurobehavioral disorder related to clinically significant levels of inattention, hyperactivity, and/or impulsivity. ADHD begins in childhood and symptoms persist into adulthood for the majority of those with the disorder. Associated features of ADHD include emotion dysregulation and cognitive impairments, which contribute to the considerable functional impairments in this disorder. Current approved treatments are reasonably effective; however, a significant need remains for new pharmacotherapies, both for individuals who do not achieve a full therapeutic response and for symptoms that are under-treated including cognition and emotion regulation. The striking relationship between ADHD and cigarette smoking and the known effects of nicotine on cognition has spurred research into the therapeutic potential of nicotinic agents for ADHD. Although there are no approved medications for ADHD that target nicotinic acetylcholine receptor (nAChR) function, results from many trials of nicotinic drugs are available and reviewed in this article. ADHD symptoms were reduced in the majority of published studies of nicotine and novel α4β2 nicotinic agonists in adult ADHD. The drugs were generally well tolerated, with mild to moderate side effects reported, which were largely consistent with cholinergic stimulation and included nausea, dizziness, and gastrointestinal distress. Within-subject crossover study designs were used in the majority of positive studies. This design may be particularly useful in ADHD trials because it minimizes variability in this notoriously heterogeneous diagnostic group. In addition, many studies found evidence for a beneficial effect of nicotinic stimulation on cognitive and emotional domains. Thus, targeting nAChRs in ADHD appears to have a modest clinical benefit in adult ADHD. Continued refinement of nAChR agonists with greater specificity and fewer side effects may lead to even more effective nAChR agonists for ADHD. Future clinical trials in ADHD should include direct measures of neuropsychological performance and emotion regulation.

Nicotinic acetylcholine receptors in attention circuitry: the role of layer VI neurons of prefrontal cortex

Cholinergic modulation of prefrontal cortex is essential for attention. In essence, it focuses the mind on relevant, transient stimuli in support of goal-directed behavior. The excitation of prefrontal layer VI neurons through nicotinic acetylcholine receptors optimizes local and top-down control of attention. Layer VI of prefrontal cortex is the origin of a dense feedback projection to the thalamus and is one of only a handful of brain regions that express the α5 nicotinic receptor subunit, encoded by the gene chrna5. This accessory nicotinic receptor subunit alters the properties of high-affinity nicotinic receptors in layer VI pyramidal neurons in both development and adulthood. Studies investigating the consequences of genetic deletion of α5, as well as other disruptions to nicotinic receptors, find attention deficits together with altered cholinergic excitation of layer VI neurons and aberrant neuronal morphology. Nicotinic receptors in prefrontal layer VI neurons play an essential role in focusing attention under challenging circumstances. In this regard, they do not act in isolation, but rather in concert with cholinergic receptors in other parts of prefrontal circuitry. This review urges an intensification of focus on the cellular mechanisms and plasticity of prefrontal attention circuitry. Disruptions in attention are one of the greatest contributing factors to disease burden in psychiatric and neurological disorders, and enhancing attention may require different approaches in the normal and disordered prefrontal cortex.

Adult attention-deficit/hyperactivity disorder and nicotine use: a qualitative study of patient perceptions

BACKGROUND

Adult Attention-Deficit/Hyperactivity Disorder (ADHD) is associated with high rates of comorbid substance use disorders, and cigarette smoking has a particularly high prevalence in this population. However, there is an ongoing debate as to whether this tobacco use is an attempt at "self-medication" or due to behavioral disinhibition. There is a surprising lack of qualitative studies that investigate the subjective perceptions of adults with ADHD regarding cigarette smoking. The present study was designed to fill this gap in the literature.

METHODS

We recruited twelve adult patients with ADHD and comorbid tobacco use from our ADHD consultation service, an outpatient facility of the Zurich University Psychiatric Hospital. Subjects were interviewed using qualitative methodology, and Mayring's qualitative content analysis was used to evaluate findings.

RESULTS

We identified two explanatory models linking ADHD and tobacco use: smoking as an attempt at self-medication and "smoking as a social behavior". On one hand, subjects considered tobacco a therapeutic aid, reporting positive effects on "inner tension" and cognitive function, and noted possible antidepressant properties as well. On the other hand, subjects considered smoking to enhance social functioning and to have a positive impact on interpersonal relationships. The majority believed that stimulant medications offered only a transient decrease in patterns of tobacco use because their ability to reduce nicotine cravings wore off quickly. Others believed that stimulants had no effect or even reinforced cigarette use.

CONCLUSIONS

Participants had different views about the link between cigarette smoking and ADHD. While the majority thought of nicotine as a sort of therapy, viewing smoking as a way to self-medicate symptoms of ADHD, motivations for nicotine use were also related to self-image, desire to belong to a peer-group, and a drive to undermine perceived social norms. Ultimately, these findings can be used by clinicians to improve treatment alliance and collaboration.

AZD3480, a novel nicotinic receptor agonist, for the treatment of attention-deficit/hyperactivity disorder in adults

BACKGROUND

Laboratory studies have found that acute stimulation of nicotinic acetylcholine receptors improves cognition in adult attention-deficit/hyperactivity disorder (ADHD). Clinical trials of nicotinic agonists have been mixed, underscoring the need to understand the mechanisms for individual differences in clinical response. Using cognitive models within a clinical trial framework may provide insight into these differences.

METHODS

This was a within-subjects, randomized, placebo-controlled double-blind trial of the nicotinic agonist AZD3480 (also termed TC-1734) at doses of 5 mg and 50 mg and placebo in adults with ADHD. The order of the 2-week treatment periods was randomized, and a 3-week wash out separated each drug treatment period. Response inhibition (Stop Signal Task [SST]) and clinical efficacy (Investigator Rated Conners Adult ADHD Rating Scale [CAARS-INV]) were the a priori primary outcome measures of cognitive and clinical effects. We hypothesized that AZD3480 treatment would improve SST performance and clinical symptoms (CAARS-INV Total ADHD Symptoms Score).

RESULTS

Thirty subjects were randomized, with 24 included in the intent-to-treat analyses. SST performance and total ADHD symptoms were significantly improved with 50 mg of AZD3480. CAARS-INV ratings of inattention, memory problems, and emotional lability/impulsivity were significantly improved with 50 mg of AZD3480.

CONCLUSIONS

These results support previous work suggesting that nicotinic agonists are viable as treatments for adult ADHD. Measuring cognitive endophenotypes related to both the disorder and mechanism of treatment may help further rational drug development for dimensional features that cross-cut psychiatric disorders.

Cognition as a therapeutic target in late-life depression: potential for nicotinic therapeutics

Depression is associated with impairments to cognition and brain function at any age, but such impairments in the elderly are particularly problematic because of the additional burden of normal cognitive aging and in some cases, structural brain pathology. Individuals with late-life depression exhibit impairments in cognition and brain structural integrity, alongside mood dysfunction. Antidepressant treatment improves symptoms in some but not all patients, and those who benefit may not return to the cognitive and functional level of nondepressed elderly. Thus, for comprehensive treatment of late-life depression, it may be necessary to address both the affective and cognitive deficits. In this review, we propose a model for the treatment of late-life depression in which nicotinic stimulation is used to improve cognitive performance and improve the efficacy of an antidepressant treatment of the syndrome of late-life depression. The cholinergic system is well-established as important to cognition. Although muscarinic stimulation may exacerbate depressive symptoms, nicotinic stimulation may improve cognition and neural functioning without a detriment to mood. While some studies of nicotinic subtype specific receptor agonists have shown promise in improving cognitive performance, less is known regarding how nicotinic receptor stimulation affects cognition in depressed elderly patients. Late-life depression thus represents a new therapeutic target for the development of nicotinic agonist drugs. Parallel treatment of cognitive dysfunction along with medical and psychological approaches to treating mood dysfunction may be necessary to ensure full resolution of depressive illness in aging.

Methylphenidate does not influence smoking-reinforced responding or attentional performance in adult smokers with and without attention deficit hyperactivity disorder (ADHD)

Individuals with Attention Deficit Hyperactivity Disorder (ADHD) smoke cigarettes at rates higher than the general population and questions have been raised about how stimulant drugs-the frontline pharmacological treatment for ADHD-influence smoking risk and behavior in those with ADHD. In the present study adult regular smokers with (n = 16) and without (n = 17) ADHD participated in 3 experimental sessions in which they completed a Progressive Ratio (PR) task to measure the relative reinforcing effects of cigarette smoking and money after oral administration of placebo and 2 active doses of methylphenidate (10 mg and 40 mg). We also measured attention and inhibitory control via a Continuous Performance Test (CPT). Methylphenidate had no effect on smoking-reinforced responding, attention, or inhibitory control in either group. Attention and inhibitory control were associated with smoking-reinforced responding, but unsystematically and only in the non-ADHD group. Several design features, such as the value of the monetary response option, the PR schedule, and the potential effects of smoking on attention and inhibitory control, could have contributed to the negative findings and are discussed as such. Although inconsistent with some previous human laboratory studies of stimulant drugs and smoking, results are consistent with recent trials of stimulant drugs as adjuncts for smoking cessation in adult smokers with ADHD. In general, methylphenidate at mild and moderate doses did not influence the relative reinforcing effects of cigarette smoking in adults with and without ADHD.

The effect of nicotine on sensorimotor gating is modulated by a CHRNA3 polymorphism

RATIONALE

Prepulse inhibition (PPI) of the acoustic startle response, a measure of sensorimotor gating, can be enhanced by nicotine. Moreover, the TT genotype of the nicotinic acetylcholine receptor (nAChR) α3-subunit (CHRNA3) rs1051730 polymorphism has previously been associated with diminished PPI and nicotine dependence.

OBJECTIVES

We tested whether this CHRNA3 polymorphism also modulates the nicotine-induced enhancement of PPI.

METHODS

We assessed the effect of nicotine on PPI, startle reactivity, and habituation in 52 healthy nonsmoking volunteers genotyped for CHRNA3 rs1051730 in a double-blind, placebo-controlled, counterbalanced, within-subjects design. Additionally, cotinine plasma levels were measured.

RESULTS

Nicotine significantly enhanced PPI in TT homozygotes only and tended to worsen PPI in TC and CC carriers. Additionally, nicotine significantly reduced startle habituation.

CONCLUSIONS

The present findings imply that the effect of nicotine on sensorimotor gating is modulated by nAChR α3-subunits. Thus, genetic variation in nicotinic receptor genes might be an important connecting link between early attentional processes and smoking behavior.

Nicotine enhances antisaccade performance in schizophrenia patients and healthy controls

Nicotine has been proposed to be a cognitive enhancer, particularly in schizophrenia patients. So far, the published studies of nicotine effects on antisaccade performance in schizophrenia patients only tested participants who were deprived smokers. Thus, we aimed to test both smoking and non-smoking patients as well as healthy controls in order to extend previous findings. Moreover, we employed a paradigm using standard and delayed trials. We hypothesized that, if nicotine is a genuine cognitive enhancer, its administration would improve antisaccade performance both in smoking and non-smoking participants. A total of 22 patients with schizophrenia (12 smokers and 10 non-smokers) and 26 controls (14 smokers and 12 non-smokers) completed the study. The effects of a nicotine patch (14 mg for smokers, 7 mg for non-smokers) on antisaccade performance were tested in a randomized, double-blind, placebo-controlled, cross-over trial. Schizophrenia patients made significantly more antisaccade errors than controls (p = 0.03). Both patients and controls made fewer antisaccade errors in the delayed trials than in the standard trials (p < 0.0001). Nicotine significantly reduced antisaccade error rate in the standard trials, but not in the delayed trials (p = 0.02). Smoking status did not influence the nicotine effect on antisaccade error rate (p = 0.10) indicating an equal procognitive effect of nicotine in smokers and non-smokers. Overall the present findings indicate that beneficial effects of nicotine on antisaccade performance are not confined to smoking schizophrenia patients. Instead, the findings likely represent genuine nicotine-induced enhancement of cognitive performance.

Reward learning as a potential target for pharmacological augmentation of cognitive remediation for schizophrenia: a roadmap for preclinical development

Rationale: Impaired cognitive abilities are a key characteristic of schizophrenia. Although currently approved pharmacological treatments have demonstrated efficacy for positive symptoms, to date no pharmacological treatments successfully reverse cognitive dysfunction in these patients. Cognitively-based interventions such as cognitive remediation (CR) and other psychosocial interventions however, may improve some of the cognitive and functional deficits of schizophrenia. Given that these treatments are time-consuming and labor-intensive, maximizing their effectiveness is a priority. Augmenting psychosocial interventions with pharmacological treatments may be a viable strategy for reducing the impact of cognitive deficits in patients with schizophrenia.

Objective: We propose a strategy to develop pharmacological treatments that can enhance the reward-related learning processes underlying successful skill-learning in psychosocial interventions. Specifically, we review clinical and preclinical evidence and paradigms that can be utilized to develop these pharmacological augmentation strategies. Prototypes for this approach include dopamine D1 receptor and α7 nicotinic acetylcholine receptor agonists as attractive targets to specifically enhance reward-related learning during CR.

Conclusion: The approach outlined here could be used broadly to develop pharmacological augmentation strategies across a number of cognitive domains underlying successful psychosocial treatment.

The effect of withdrawal and intake of nicotine on smokers' ability to ignore distractors in a number parity decision task

Nicotine's attention enhancing effects are often attributed to enhancement of stimulus filtering by the attention networks. We investigated distractibility in 20 abstinent cigarette smokers (9 hours overnight; phase 1) and tested them again after smoking one cigarette (phase 2). Their performance was compared to 20 nonsmokers (no nicotine intake). In an auditory number parity decision task, participants had to make a forced choice "odd" or "even" decision about centrally presented numbers between 2 and 9, while ignoring laterally presented preceding or simultaneous novel distractors. In phase 1, distractors that preceded goal stimuli slowed reaction times (RTs) more than simultaneously presented distractors in both groups. In phase 2, nicotine intake speeded RTs in smokers in all conditions and reduced RT variability for simple number decisions and simultaneous distractors. Overall, there was a nonsignificant trend for smokers to be less accurate than nonsmokers. Accuracy in the simultaneous distractor condition decreased in both groups in phase 2. We argue that the observed nicotine-induced improvements on behavioral performance primarily reflect enhancement of top-down control of attention.

Role of α7- and α4β2-nAChRs in the neuroprotective effect of nicotine in stress-induced impairment of hippocampus-dependent memory

We have previously shown that nicotine prevents stress-induced memory impairment. In this study, we have investigated the role of α7- and α4β2-nicotinic acetylcholine receptors (nAChRs) in the protective effect of nicotine during chronic stress conditions. Chronic psychosocial stress was induced using a form of rat intruder model. During stress, specific antagonist for either α7-nAChRs [methyllycaconitine (MLA)] or α4β2-nAChRs [dihydro-β-erythroidine (DHβE)] was infused into the hippocampus using a 4-wk osmotic pump at a rate of 82 μg/side.d and 41 μg/side.d, respectively. Three weeks after the start of infusion, all rats were subjected to a series of cognitive tests in the radial arm water maze (RAWM) for six consecutive days or until the animal reached days to criterion (DTC) in the fourth acquisition trial and in all memory tests. DTC is defined as the number of days the animal takes to make no more than one error in three consecutive days. In the short-term memory test, MLA-infused stressed/nicotine-treated rats made similar errors to those of stress and significantly more errors compared to those of stress/nicotine, nicotine or control groups. This finding was supported by the DTC values for the short memory tests. Thus, MLA treatment blocked the neuroprotective effect of nicotine during chronic stress. In contrast, DHβE infusion did not affect the RAWM performance of stress/nicotine animals. These results strongly suggest the involvement of α7-nAChRs, but not α4β2-nAChRs, in the neuroprotective effect of chronic nicotine treatment during chronic stress conditions.

Investigating the impact of nicotine on executive functions using a novel virtual reality assessment

AIMS

Nicotine is known to enhance aspects of cognitive functioning in abstinent smokers, but the effects on specific areas of executive functions and in non-smokers are inconclusive. This may be due in part to the poor sensitivity of tests used to assess executive functions. This study used a new virtual reality assessment of executive functions known as JEF (the Jansari assessment of Executive Functions) to address this issue.

DESIGN

A 2 × 2 design manipulating group (smokers and never-smokers) and drug [nicotine (4 mg for smokers; 2 mg for never smokers) versus placebo gum].

SETTING

School of Psychology; University of East London.

PARTICIPANTS

Seventy-two participants (aged 18-54 years): 36 minimally deprived (2 hours) smokers and 36 never-smokers.

MEASUREMENTS

Components of executive function were measured using the virtual reality paradigm JEF, which assesses eight cognitive constructs simultaneously as well as providing an overall performance measure.

FINDINGS

Univariate analyses of variance revealed that nicotine improved overall JEF performance, time-based prospective memory and event-based prospective memory in smokers (P < 0.01), but not in never-smokers. Action-based prospective memory was enhanced in both groups (P < 0.01) and never-smokers out-performed smokers on selective thinking and adaptive thinking (P < 0.01).

CONCLUSIONS

Executive functioning and prospective memory as aspects of cognitive performance can be enhanced by nicotine gum in smokers who have abstained for as little as 2 hours.

High density of nicotinic receptors in the cingulo-insular network

The nicotinic system plays an important role in ordinary cognition, particularly in attention. The main nicotinic receptor in the human brain is the heteromeric α4β2 neuronal nicotinic acetylcholine receptor (nAChR), which is distributed throughout the brain, with an especially high density in the thalamus and brainstem. Despite the important role of α4β2 nAChRs in various physiological functions and pathological conditions, their distribution in the human cortex remains poorly characterized. We assessed the in vivo distribution of α4β2 nAChRs in the human cortex in a group of seven non-smoking healthy subjects, using 2-[(18)F]F-A-85380 PET and a volume-of-interest-based analysis. We showed that cortical nAChR density was highest in the insular and anterior cingulate cortices. In functional magnetic resonance imaging studies, these two cortical regions and the thalamus have been shown to be highly correlated during the resting state and various tasks. Here, we also directly assessed nAChR density in this cingulo-insular network as defined in an independent dataset using resting-state functional connectivity, and compared it to other control-related networks, to the default mode network as well as to sensory and motor networks. Receptor density was significantly higher in the cingulo-insular network. This network has been suggested to maintain a variety of foundational capacities fundamental to cognitive function. The demonstration of a high nAChR density in the insular and anterior cingulate cortices reflects a particular neurochemical organization of the cingulo-insular network, and suggests an important role of the nicotinic receptors in its functions.

Attention-deficit/hyperactivity disorder (ADHD) symptoms, craving to smoke, and tobacco withdrawal symptoms in adult smokers with ADHD

BACKGROUND

Tobacco withdrawal symptoms may be confounded with attention-deficit/hyperactivity disorder (ADHD) symptoms among smokers with ADHD.

OBJECTIVE

(1) To assess overlap between ADHD symptoms and tobacco/nicotine withdrawal symptoms and craving; (2) to assess the relationship between craving or withdrawal symptoms and the effect of osmotic-release oral system methylphenidate (OROS-MPH) on ADHD symptoms; (3) to assess the association of ADHD symptoms, craving, and withdrawal symptoms with abstinence.

METHODS

Secondary analysis of a randomized, placebo controlled smoking cessation trial assessing the efficacy of OROS-MPH taken in addition to nicotine patch among individuals with ADHD. ADHD symptoms, withdrawal symptoms, and craving were assessed at baseline and 2, 4 and 6 weeks after a target quit day.

RESULTS

Withdrawal symptoms and craving showed limited and modest overlap with ADHD symptoms prior to abstinence but more extensive and stronger correlation after quit day. Compared to placebo, OROS-MPH reduced ADHD symptoms; this effect was attenuated by controlling for withdrawal symptoms, but not by craving. Craving, but not ADHD symptoms and withdrawal symptoms, was associated with abstinence during the trial.

CONCLUSION

When treating smokers with ADHD (1) craving, rather than tobacco withdrawal symptoms or ADHD symptoms may be the more effective therapeutic smoking cessation targets; (2) careful distinction of craving, withdrawal symptoms, and ADHD symptoms when assessing withdrawal phenomena is needed.

Nicotine improves performance in an attentional set shifting task in rats

A large number of studies in both humans and experimental animals have demonstrated nicotine-induced improvements in various aspects of cognitive function, including attention and memory. The prefrontal cortex (PFC) is thought to be critically involved in the modulation of executive function and these attentional processes are enhanced by nicotine acting at nicotinic acetylcholine receptors. The involvement of nicotinic processes on cognitive flexibility in particular has not been specifically investigated. The effects of nicotine on attentional flexibility were therefore evaluated using the rodent attentional set shifting task in rats. Nicotine injected both acutely and following repeated pre-exposure significantly improved both intradimensional and extradimensional set shifting performance in the task. Further investigation of the acute effects of nicotine demonstrated this improvement in attentional flexibility to be dose-dependent. These results implicate the nicotinic receptor system in the mediation of processes underlying cognitive flexibility and suggest that nicotine improves attentional flexibility in rats, both within and between perceptual dimensions of a compound stimulus. Nicotine-induced alterations in prefrontal circuitry may underlie these effects on cognitive flexibility. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Lower but not higher doses of transdermal nicotine facilitate cognitive performance in smokers on gender non-preferred tasks

One of the most widely used treatments for smoking cessation is nicotine replacement therapy (NRT). There is some evidence that smokers experience abstinence-induced deficits in cognitive function, which are attenuated by NRTs. Additionally it's been suggested that the degree of reversal of cognitive deficits may depend on the NRT dose and the smoker's gender. In the present placebo-controlled study we investigated effects of three doses of transdermal nicotine (7 mg, 14 mg and 21 mg) on cognitive performance of 48 male and 48 female smokers after overnight abstinence and 6h of patch application. Cognitive tasks used in the study included the Conners' CPT, emotional Stroop, mental arithmetic, and verbal recall of affective prose passages. The results showed greater probability of attentional problems in the male sample compared to females as identified by the Conners' CPT. Within gender women showed improved performance in the 7 mg and 14 mg conditions on several measures of the Conners' CPT, and faster hit reaction time on the emotional Stroop test compared to women in the placebo and 21 mg of nicotine groups. Conversely, males showed a moderate overall advantage on the mental arithmetic task and were differentially sensitive to nicotine treatment on the prose recall task, on which the greatest improvement in recall of affective material was observed for the 14 mg group compared to the 21 mg group. The results are explained on the basis of an inverted U-shaped relationship between nicotinic stimulation and cognitive performance as well as greater sensitivity to nicotine dose manipulation on gender non-preferred cognitive tasks.

Nicotine differentially modulates antisaccade performance in healthy male non-smoking volunteers stratified for low and high accuracy

RATIONALE

Nicotinergic agents are currently examined as possible pro-cognitive drugs for a variety of clinical conditions marked by cognitive deficits, such as attention deficit hyperactivity disorder (ADHD) or schizophrenia. The response to acute nicotine is heterogeneous across subjects and samples; however, only a few reliable predictors of response have been identified.

OBJECTIVES

We tested the hypothesis that baseline performance level in cognitive control may be a predictor of the cognitive effects of nicotine.

METHODS

We tested 28 healthy Caucasian, male, non-smoking volunteers with the antisaccade task, an oculomotor measure of cognitive control. Participants were given a 7-mg nicotine patch in a double-blind, placebo-controlled, counterbalanced, within-subjects design. Subjects were stratified into high and low performers based on their antisaccade error rate in the placebo condition (median split).

RESULTS

Nicotine tended to reduce response time variability of prosaccade latency (p = 0.06). There was no main effect of nicotine on antisaccade error rate (p = 0.31). However, nicotine significantly reduced antisaccade error rate in the low-accuracy probands while leaving performance of the high-accuracy probands unaffected (interaction, p < 0.05). Furthermore, we found a nicotine-induced reduction of response time variability of antisaccade latency at one target location in the low-performing group (interaction, p < 0.05).

CONCLUSIONS

The present results demonstrate the importance of baseline performance differences for the effectiveness of pharmacological enhancement of cognitive control. More generally, the results suggest that stimulation of the nicotinic acetylcholine receptor system might be an effective way of improving cognition in people with poor cognitive performance, such as patients with ADHD or schizophrenia.

Substance use in college students with ADHD

OBJECTIVE

The college years represent a developmental transition during which the initiation and escalation of heavy drinking set the stage for lifelong difficulties with alcohol and other drugs. Evidence from studies of adolescents and young adults with ADHD suggests that college students with the disorder may be uniquely vulnerable to alcohol- and drug-related problems. However, no studies have examined substance use in college students with ADHD.

METHOD

Tobacco, alcohol, illicit drug use, and associated impairment were examined in 91 college students with (n = 53) and without (n = 38) ADHD.

RESULTS

ADHD was associated with increased frequency of tobacco use, higher rates of dangerous or hazardous patterns of alcohol use, and higher levels of impairment related to marijuana and nonmarijuana illicit drug use, independent of conduct disorder history.

CONCLUSION

These findings suggest that college students with ADHD may be at elevated risk for problematic patterns of substance use.

Sex, ADHD symptoms, and smoking outcomes: an integrative model

Both females and individuals with Attention-Deficit/Hyperactivity Disorder (ADHD) have been found to be at increased risk for a range of smoking outcomes, and recent empirical findings have suggested that women with ADHD may be particularly vulnerable to nicotine dependence. On a neurobiological level, the dopamine reward processing system may be implicated in the potentially unique interaction of nicotine with sex and with ADHD status. Specifically, nicotine appears to mitigate core ADHD symptoms through interaction with the dopamine reward processing system, and ovarian hormones have been found to interact with nicotine within the dopamine reward processing system to affect neurotransmitter release and functioning. This article synthesizes data from research examining smoking in women and in individuals with ADHD to build an integrative model through which unique risk for cigarette smoking in women with ADHD can be systematically explored. Based upon this model, the following hypotheses are proposed at the intersection of each of the three variables of sex, ADHD, and smoking: (1) individuals with ADHD have altered functioning of the dopamine reward system, which diminishes their ability to efficiently form conditioned associations based on environmental contingencies; these deficits are partially ameliorated by nicotine; (2) nicotine interacts with estrogen and the dopamine reward system to increase the positive and negative reinforcement value of smoking in female smokers; (3) in adult females with ADHD, ovarian hormones interact with the dopamine reward system to exacerbate ADHD-related deficits in the capacity to form conditioned associations; and (4) during different phases of the menstrual cycle, nicotine and ovarian hormones may interact differentially with the dopamine reward processing system to affect the type and value of reinforcement smoking provides for women with ADHD. Understanding the bio-behavioral mechanisms underlying cigarette addiction in specific populations will be critical to developing effectively tailored smoking prevention and cessation programs for these groups. Overall, the goal of this paper is to examine the interaction of sex, smoking, and ADHD status within the context of the dopamine reward processing system not only to elucidate potential mechanisms specific to female smokers with ADHD, but also to stimulate consideration of how the examination of such individual differences can inform our understanding of smoking more broadly.

Delayed procedural learning in α7-nicotinic acetylcholine receptor knockout mice

The α7-nicotinic acetylcholine receptor (nAChR) has long been a procognitive therapeutic target to treat schizophrenia. Evidence on the role of this receptor in cognition has been lacking, however, in part due to the limited availability of suitable ligands. The behavior of α7-nAChR knockout (KO) mice has been examined previously, but cognitive assessments using tests with cross-species translatability have been limited to date. Here, we assessed the cognitive performance of α7-nAChR KO and wild-type (WT) littermate mice in the attentional set-shifting task of executive functioning, the radial arm maze test of spatial working memory span capacity and the novel object recognition test of short-term memory. The reward motivation of these mutants was assessed using the progressive ratio breakpoint test. In addition, we assessed the exploratory behavior and sensorimotor gating using the behavioral pattern monitor and prepulse inhibition, respectively. α7-nAChR KO mice exhibited normal set-shifting, but impaired procedural learning (rule acquisition) in multiple paradigms. Spatial span capacity, short-term memory, motivation for food, exploration and sensorimotor gating were all comparable to WT littermates. The data presented here support the notion that this receptor is important for such procedural learning, when patterns in the environment become clear and a rule is learned. In combination with the impaired attention observed previously in these mice, this finding suggests that agonist treatments should be examined in clinical studies of attention and procedural learning, perhaps in combination with cognitive behavioral therapy.

Development of the motivational system during adolescence, and its sensitivity to disruption by nicotine

The brain continues to develop during adolescence, and exposure to exogenous substances such as nicotine can exert long-lasting adaptations during this vulnerable period. In order to fully understand how nicotine affects the adolescent brain it is important to understand normal adolescent brain development. This review summarizes human and animal data on brain development, with emphasis on the prefrontal cortex, for its important function in executive control over behavior. Moreover, we discuss how nicotine exposure during adolescence can disrupt brain development bearing long-term consequences on executive cognitive function in adulthood.