Society for Research on Nicotine and Tobacco. Third Annual Scientific Conference, Nashville, Tennessee, USA, 13-14 June 1997

Nicotine-induced cortical activation among nonsmokers with moderation by trait cognitive control

RATIONALE

Considerable research suggests that nicotine enhances cognitive control-related processes (e.g., attention, memory) among nicotine-deprived smokers, both in terms of behavior and neural indices (e.g., ERP, slow-wave EEG). Nicotine may also increase cognitive control among nonsmokers, and this may vary as a function of trait cognitive control. It is important to examine the effects of nicotine on cognitive control-related processes among nonsmokers as these effects may provide a path for the initiation of smoking.

OBJECTIVES

The objectives of the study were to examine in nonsmokers (1) the effect of nicotine on resting cortical activity, an indirect measure of cognitive control, and (2) trait cognitive control as a moderator of nicotine-induced cortical activity changes.

METHOD

Eighty participants were given placebo and 7-mg nicotine patches in separate sessions for this counter-balanced, double-blind, within-subject study. Resting cortical activity was measured with EEG for a 3-min period with eyes opened.

RESULTS

Average alpha-1 band power density values in frontal and central regions were lower during the nicotine versus placebo condition, which provides evidence of nicotine-induced cortical activation. Furthermore, those with lower self-reported cognitive control exhibited greater nicotine-induced reductions in alpha-1 power density values.

CONCLUSIONS

These individual differences in nicotine-induced cortical activation are consistent with a model of nicotine self-medication whereby individuals with lower cognitive control may find smoking more reinforcing via amelioration of related cognitive deficits.

Current smoking and reduced gray matter volume-a voxel-based morphometry study

Nicotine modulates prefrontal processing when tested with functional imaging. Previous studies on changes in regional brain volumes in small samples, reporting different life-time exposure to nicotine, identified reduced volume in smokers in prefrontal areas but reported controversial results for other areas. We investigated the association of cigarette smoking and regional gray and white matter volume by using voxel-based morphometry (VBM) for T1-weighted high-resolution magnetic resonance imaging in 315 current-smokers and 659 never-smokers from the representative Study of Health in Pomerania (SHIP). Our study showed that in current-smokers smoking is significantly associated with gray matter volume loss in the prefrontal cortex, the anterior cingulate cortex, the insula, and the olfactory gyrus. White matter volumes were not relevantly reduced in current-smokers. In current-smokers, we found associations of gray matter loss and smoking exposure (pack-years) in the prefrontal cortex, the anterior and middle cingulate cortex, and the superior temporal and angular gyrus, which however did not stand corrections for multiple testing. We confirmed associations between smoking and gray matter differences in the prefrontal cortex, the anterior cingulate cortex and the insula in the general population of Pomerania (Germany). For the first time, we identified differences in brain volumes in the olfactory gyrus. Other cerebral regions did not show significant differences when correcting for multiple comparisons within the whole brain. The regions of structural deficits might be involved in addictive behavior and withdrawal symptoms, whereas further investigations have to show if the observed atrophies were caused by smoking itself or are preexisting differences between smoking and non-smoking individuals.

Effects of smoking on the acoustic startle response and prepulse inhibition in smokers with and without posttraumatic stress disorder

RATIONALE

Cigarette smokers smoke in part because nicotine helps regulate attention. Prepulse inhibition (PPI) of the startle reflex is a measure of early attentional gating that is reduced in abstinent smokers and in groups with attention regulation difficulties. Attention difficulties are found in people with posttraumatic stress disorder (PTSD).

OBJECTIVES

The aim of this study is to assess whether smoking and abstinence differentially affect the startle response and PPI in smokers with and without PTSD.

METHODS

Startle response and PPI (prepulses at 60, 120, or 240 ms) were measured in smokers with (N = 39) and without (N = 61) PTSD, while smoking and again while abstinent.

RESULTS

Participants with PTSD produced both larger magnitude and faster latency startle responses than controls. Across groups, PPI was greater when smoking than when abstinent. The PTSD and control group exhibited different patterns of PPI across prepulse intervals when smoking and when abstinent. Older age was associated with reduced PPI, but only when abstinent from smoking.

CONCLUSIONS

The effects of PTSD on startle magnitude and of smoking on PPI replicate earlier studies. The different pattern of PPI exhibited in PTSD and control groups across prepulse intervals, while smoking and abstinent suggests that previous research on smoking and PPI has been limited by not including longer prepulse intervals, and that nicotine may affect the time course as well as increasing the level of PPI. The reduced PPI among older participants during abstinence suggests that nicotine may play a role in maintaining attention in older smokers, which may motivate continued smoking in older individuals.

Greater risk sensitivity of dorsolateral prefrontal cortex in young smokers than in nonsmokers

RATIONALE

Despite a national reduction in the prevalence of cigarette smoking, ~19% of the adult US population persists in this behavior, with the highest prevalence among 18-25-year-olds. Given that the choice to smoke imposes a known health risk, clarification of brain function related to decision-making, particularly involving risk-taking, in smokers may inform prevention and smoking cessation strategies.

OBJECTIVES

This study aimed to compare brain function related to decision-making in young smokers and nonsmokers.

METHODS

The Balloon Analogue Risk Task (BART) is a computerized risky decision-making task in which participants pump virtual balloons, each pump associated with an incremental increase in potential payoff on a given trial but also with greater risk of balloon explosion and loss of payoff. We used this task to compare brain activation associated with risky decision-making in smokers (n = 18) and nonsmokers (n = 25), while they performed the BART during functional magnetic resonance imaging (fMRI). The participants were young men and women, 17-21 years of age.

RESULTS

Risk level (number of pumps) modulated brain activation in the right dorsolateral and ventrolateral prefrontal cortices more in smokers than in nonsmokers, and smoking severity (Heaviness of Smoking Index) was positively related to this modulation in an adjacent frontal region.

CONCLUSIONS

Given evidence for involvement of the right dorsolateral and ventrolateral prefrontal cortices in inhibitory control, these findings suggest that young smokers have a different contribution of prefrontal cortical substrates to risky decision-making than nonsmokers. Future studies are warranted to determine whether the observed neurobiological differences precede or result from smoking.

Effects of intravenous nicotine on prepulse inhibition in smokers and non-smokers: relationship with familial smoking

RATIONALE

The reinforcing properties of nicotine may be, in part, derived from its ability to enhance certain forms of cognitive processing. Several animal and human studies have shown that nicotine increases prepulse inhibition (PPI) of the startle reflex. However, it remains unclear whether these effects are related to smoking susceptibility.

OBJECTIVES

The current study examined the effects of intravenously delivered nicotine on PPI in smokers and non-smokers, as well as its association with a quantitative index of familial smoking.

METHODS

The sample consisted of 30 non-smokers and 16 smokers, who completed an initial assessment, followed on a separate day by a laboratory assessment of PPI prior to and following each of two intravenous nicotine infusions. Separate doses were used in smoker and non-smoker samples.

RESULTS

Analyses indicated that both nicotine infusions acutely enhanced PPI among non-smokers, and this enhancement was positively related to the degree of smoking among first and second-degree relatives. Smokers also displayed PPI enhancement after receiving the first infusion, but this effect was unrelated to familial smoking.

CONCLUSIONS

These data suggest that the PPI paradigm may have utility as an endophenotype for cognitive processes which contribute to smoking risk.

Cognitive mechanisms underlying relapse to nicotine

Much of the addictive power of nicotine in humans may be attributable to learned contextual associations, such that these secondary cues become potent predictive incentives for both maintaining and driving relapse to drug use, even after long periods of abstinence. Here, I review the evidence that chronic nicotine in vivo can induce persistent neuronal changes in excitability within the hippocampal circuitry, with a specific emphasis on the dentate gyrus as an initiator of drug use. The relevance of these early homeostatic (can be fully reversed by acute application of nicotine) neuroadaptations on withdrawal from nicotine is then related to known cognitive deficits also produced following chronic nicotine. I briefly discuss how the hippocampus may influence other parts of the reward circuitry to affect chronic drug use and how periods of drug cessation and/or withdrawal may convert these short-term changes into permanent alterations within the brain that may drive craving and/or relapse many years of abstinence.

Meta-analysis of the acute effects of nicotine and smoking on human performance

RATIONALE AND OBJECTIVE

Empirical studies indicate that nicotine enhances some aspects of attention and cognition, suggesting a role in the maintenance of tobacco dependence. The purpose of this review was to update the literature since our previous review (Heishman et al. Exp Clin Psychopharmacol 2:345-395, 1994) and to determine which aspects of human performance were most sensitive to the effects of nicotine and smoking.

METHODS

We conducted a meta-analysis on the outcome measures of 41 double-blind, placebo-controlled laboratory studies published from 1994 to 2008. In all studies, nicotine was administered, and performance was assessed in healthy adult nonsmokers or smokers who were not tobacco-deprived or minimally deprived (

RESULTS

There were sufficient effect size data to conduct meta-analyses on nine performance domains, including motor abilities, alerting and orienting attention, and episodic and working memory. We found significant positive effects of nicotine or smoking on six domains: fine motor, alerting attention-accuracy and response time (RT), orienting attention-RT, short-term episodic memory-accuracy, and working memory-RT (effect size range = 0.16 to 0.44).

CONCLUSIONS

The significant effects of nicotine on motor abilities, attention, and memory likely represent true performance enhancement because they are not confounded by withdrawal relief. The beneficial cognitive effects of nicotine have implications for initiation of smoking and maintenance of tobacco dependence.

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Key Words

• nicotine
• tobacco
• smoking
• performance
• motor
• attention
• memory
• cognition
• smokers
• nonsmokers

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MESH Headings

• Attention/drug effects
• Dose-Response Relationship, Drug
• Humans
• Memory/drug effects
• Motor Skills/drug effects
• Nicotine/administration & dosage
• Nicotine/pharmacology
• Psychomotor Performance/drug effects
• Smoking/psychology

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Grants

• T32 DA007209 NIDA NIH HHS
• ZIA DA000483-06 Intramural NIH HHS
• ZIA DA000484-06 Intramural NIH HHS
• T32DA007209-29 NIDA NIH HHS

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Affiliation(s)

Stephen J Heishman Nicotine Psychopharmacology Section, National Institute on Drug Abuse, NIH Intramural Research Program, 251 Bayview Blvd., Baltimore, MD 21224, USA.
Bethea A Kleykamp
Edward G Singleton

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Why do young women smoke? VI. A controlled study of nicotine effects on attention: pharmacogenetic interactions

In prior studies we found that young, female smokers manifest poorer performance than non-smokers on attention-related tasks and that these findings can be moderated by variation in nicotinic acetylcholine receptor (nAChR) genes. We predicted that under controlled conditions (1) nicotine would improve functioning on attentional tasks in smokers who previously manifested relatively poor performance, and that (2) smokers who carry genetic variations associated with poorer attention performance would derive greater benefit from nicotine. To test these hypotheses, 31 young female smokers, who participated in our previous study, performed the Matching Familiar Figures Test (MFFT), Tower of London Test and Continuous Performance Task (CPT) in a double-blind, within-between subject design, placebo or nicotine (4 mg as gum) serving as the within factor and genetic profile as the between factor. Repeated measures ANCOVA controlling for attention deficit symptomatology, substance abuse and nicotine dependence showed better performance under nicotine among participants with higher levels of attention deficit symptoms (MFFT errors: P=0.04; CPT commissions: P=0.01) and nicotine dependence (CPT stability of response: P=0.04) and greater consumption of caffeine (CPT stability of response: P=0.04). An interactive effect of genetic profile was demonstrated for SNP rs2337980 in CHRNA7. These findings suggest that nicotine may have stronger short-term facilitating effects on attention in women who have more attention deficit symptoms and consume more nicotine and caffeine. This effect may be modified by a specific genetic make-up. Such individuals may be at increased risk for nicotine addiction and for greater difficulties in smoking cessation.

Chronic nicotine improves cognitive performance in a test of attention but does not attenuate cognitive disruption induced by repeated phencyclidine administration

RATIONALE

Nicotine-induced cognitive enhancement may be a factor maintaining tobacco smoking, particularly in psychiatric populations suffering from cognitive deficits. Schizophrenia patients exhibit higher smoking rates compared with the general population, suggesting that attempts to self-medicate cognitive schizophrenia deficits may underlie these high smoking levels.

OBJECTIVES

The present study explored pro-cognitive effects of nicotine in a model of schizophrenia-like cognitive dysfunction to test this self-medication hypothesis.

MATERIALS AND METHODS

We investigated whether chronic nicotine (3.16 mg/kg/day, base) would attenuate the performance disruption in the five-choice serial reaction time task (5-CSRTT, a task assessing various cognitive modalities, including attention) induced by repeated administration of phencyclidine (PCP), an N-methyl-D-aspartate receptor antagonist that induces cognitive deficits relevant to schizophrenia.

RESULTS

Chronic nicotine administration shortened 5-CSRTT response latencies under baseline conditions. Nicotine-treated rats also made more correct responses and fewer omissions than vehicle-treated rats. Replicating previous studies, repeated PCP administration (2 mg/kg, 30 min before behavioral testing for two consecutive days followed 2 weeks later by five consecutive days of PCP administration) decreased accuracy and increased response latencies, premature responding, and timeout responding. Chronic nicotine did not attenuate these PCP-induced disruptions.

CONCLUSIONS

Chronic nicotine had pro-cognitive effects by itself, supporting the hypothesis that cognitive enhancement may contribute to tobacco smoking. At the doses of nicotine and PCP used, however, no support was found for the hypothesis that the beneficial effects of nicotine on cognitive deficits induced by repeated PCP administration, assessed in the 5-CSRTT, are larger than nicotine effects in the absence of PCP.

Effects of smoking abstinence on adult smokers with and without attention deficit hyperactivity disorder: results of a preliminary study

RATIONALE

Individuals with attention deficit hyperactivity disorder (ADHD) smoke at higher rates than the general population; however, little is known about the mechanisms underlying this comorbidity.

OBJECTIVE

This study evaluated the effects of overnight abstinence on withdrawal symptoms and cognitive performance in adult smokers with and without ADHD.

MATERIALS AND METHODS

Individuals smoking > or = 15 cigarettes per day were recruited from the community and underwent an evaluation to establish a diagnosis of ADHD (n = 12) or not (n = 14). Withdrawal symptoms, mood, craving, cognitive performance, and smoking cue reactivity were measured during two laboratory sessions-in a 'Satiated' condition participants smoked up to and during the session while in an 'Abstinent' condition, participants were required to be smoking abstinent overnight and remain abstinent during the session.

RESULTS

The effects of abstinence on ADHD and non-ADHD smokers did not differ for withdrawal symptom severity, mood, craving or cue reactivity. Significant Group x Condition interactions were observed for measures of attention and response inhibition on the Conners' CPT. For reaction time (RT) variability and errors of commission, the ADHD group exhibited greater decrements in performance after overnight abstinence compared to the non-ADHD group. The effects of abstinence on other cognitive measures (e.g., rapid visual information processing task, cued Go/No-Go task) did not differ between the two groups.

CONCLUSION

This preliminary study is the first to systematically evaluate the effects of acute smoking abstinence in adult smokers diagnosed with ADHD. Individuals with the disorder may smoke at higher rates due to greater worsening of attention and response inhibition after abstinence.

Dose-related enhancement of mood and cognition in smokers administered nicotine nasal spray

The discovery of the role of nicotinic receptors in attention and memory has led to the testing of nicotinic analogs as cognitive enhancing agents in patient populations. Empirical information about nicotine's ability to enhance elements of attention and memory in normal individuals might guide development of therapeutic uses of nicotine in cognitively impaired populations. The purpose of this study was to determine the effect of nicotine on continuous attention, working memory, and computational processing in tobacco-deprived and nondeprived smokers. A total of 28 smokers (14 men, 14 women) participated in a double-blind, placebo-controlled, within-subject study, in which they were overnight (12 h) tobacco deprived at one session and smoked ad libitum before the other session. At each session, participants received 0, 1, and 2 mg nicotine via nasal spray in random order at 90 min intervals. Before and after each dose, a battery of cognitive, subjective, and physiological measures was administered, and blood samples were taken for plasma nicotine concentration. Overnight tobacco deprivation resulted in impaired functioning on all cognitive tests and increased self-reports of tobacco craving and negative mood; nicotine normalized these deficits. In the nondeprived condition, nicotine enhanced performance on the continuous performance test (CPT) and an arithmetic test in a dose-related manner, but had no effect on working memory. In general, women were more sensitive than men to the subjective effects of nicotine. These results provide an unequivocal determination that nicotine enhanced attentional and computational abilities in nondeprived smokers and suggest these cognitive domains as substrates for novel therapeutic indications.

Effects of cigarette smoking and abstinence on Stroop task performance

RATIONALE

Smokers report enhanced concentration after cigarette smoking and difficulty concentrating when abstinent from smoking. These perceived effects may contribute to smoking cessation failures, and if so, clarification of their cognitive bases could inform treatment strategies. Selective attention may be important in this regard, but earlier literature presents inconsistent findings on how smoking abstinence and resumption of smoking influence this cognitive function.

OBJECTIVES

We aimed to compare smokers and nonsmokers on selective attention, and in smokers, to test the effects of overnight abstinence from smoking and of acute smoking on selective attention.

MATERIALS AND METHODS

Smokers and nonsmokers (n = 43) performed a Stroop test (two test days, two test blocks per day). Smokers participated after overnight abstinence and also within 1-h of ad libitum smoking. Smokers each smoked a cigarette between test blocks on each day; nonsmokers did not.

RESULTS

Smokers demonstrated longer response latencies for both congruent and incongruent stimuli after overnight than brief abstinence, but no deficit specifically related to selective attention. Whereas nonsmokers showed no changes in performance in the second test block, smoking between blocks reduced the Stroop effect when smokers were abstinent overnight.

CONCLUSIONS

These data are consistent with the hypothesis that abstinence from smoking among nicotine-dependent individuals has deleterious effects on cognitive performance, but do not indicate that selective attention is adversely effected. Improvement in selective attention after terminating abstinence with one cigarette may also contribute to smokers' perceived enhanced ability to concentrate after smoking.

Effect of tobacco deprivation on the attentional blink in rapid serial visual presentation

When two targets are imbedded in rapid serial visual presentation (RSVP), identification of the second target (T2) is impaired if it occurs within 500 ms of the first target (T1). This attentional blink (AB) is thought to involve interference of resources in processing T1 and T2. The deleterious effect of tobacco deprivation on attention has been documented, but no studies have examined the AB. Nonsmokers (n=30), 12-h tobacco-deprived smokers (n=30), and nondeprived smokers (n=30) were randomly assigned to perform the RSVP with one of three stimulus-duration conditions (96, 113, or 130 ms). Participants completed 48 RSVP trials. Each trial consisted of 16 individually presented words (T1, T2, and 14 distractors), and T2 lagged T1 at serial positions 1-8. Participants verbalized T1 and T2 in order immediately after each trial. Identification of T2 (for correct T1 trials) was impaired at early versus late lag positions, which was especially pronounced in the most difficult (96 ms) condition. There was no evidence for group differences on the AB; however, deprived smokers were worse identifying T1 in the 113-ms condition. These results suggest that the AB is influenced by stimulus duration, but not by 12 h of tobacco deprivation.

Transdermal nicotine attenuates depression symptoms in nonsmokers: a double-blind, placebo-controlled trial

RATIONALE

Despite established links between nicotine dependence and depression, little research has examined the effects of nicotine on depression symptoms.

OBJECTIVE

This study evaluated the acute and chronic effects of transdermal nicotine in nonsmokers with baseline depression symptoms during a 4-week, double-blind, placebo-controlled trial.

METHODS

Nonsmokers with scores >or=10 on the Center for Epidemiological Studies Depression scale (CES-D) were recruited from the community. Mood and cognitive performance were measured at baseline (day 0) and at 1, 8, 21, and 28 days. Participants were randomly assigned to wear a placebo or nicotine patch for 4 weeks (3.5 mg/day during weeks 1 and 4; 7 mg/day during weeks 2 and 3). The final sample consisted of 11 nonsmokers with a mean baseline CES-D score of 27.36 (SD=10.53).

RESULTS

Salivary nicotine levels indicated the majority of participants were compliant with treatment. Acute nicotine did not alter mood. After adjusting for baseline values, chronic nicotine resulted in a significant decline in CES-D scores at day 8 (3.5 mg/day), but returned to placebo levels by the last visit. This return to baseline levels was coincident with a decrease in nicotine administration from 7 to 3.5 mg/day. A similar trend for improved response inhibition as measured by the Conners Continuous Performance Task was also observed. Reported side effects were infrequent and minimal.

CONCLUSION

These findings suggest a role for nicotinic receptor systems in the pathophysiology of depression and that nicotinic compounds should be evaluated for treating depression symptoms.

C957T polymorphism of the dopamine D2 receptor gene modulates the effect of nicotine on working memory performance and cortical processing efficiency

RATIONALE

In both animals and humans, nicotine produces behavioral effects that vary across individuals. Studies examining the role of genetic variability in modulating individual response to nicotine in humans have increased, with recent work showing that genetic variation at the dopamine D2 receptor (DRD2) predicts response to pharmacotherapy for tobacco dependence.

OBJECTIVES

To determine whether a polymorphism of the DRD2 gene, C957T, that alters DRD2 binding availability in humans modifies the effects of nicotine on verbal working memory performance and on processing efficiency of brain regions that support verbal working memory.

MATERIALS AND METHODS

Working memory and brain function were assessed in 36 adult subjects (15,957T allele carriers and 21,957C homozygotes), each of whom was studied twice, once after placement of a placebo patch and once after placement of a nicotine patch. Brain function was assessed using functional magnetic resonance imaging while the subjects performed a verbal working memory task.

RESULTS

During performance of a task with high verbal working memory load, nicotine administration worsened performance accuracy and reduced the processing efficiency of brain regions that support phonological rehearsal during verbal working memory in carriers of the 957T allele.

CONCLUSIONS

These findings are consistent with the notion that genetic variation in DRD2 contributes to individual variation in a range of behavioral and brain responses to nicotine in humans.

Neural effects of nicotine during auditory selective attention in smokers: an event-related potential study

Acute nicotine has been found to improve task performance in smokers after smoking abstinence, but the attentional processes mediating these improvements are unclear. Since scalp-recorded event-related potentials (ERPs) have been shown to be sensitive indicators of selective attention, the effects of acutely administered nicotine were examined on ERPs and concomitant behavioural performance measures in an auditory selective attention task. Ten (6 males) overnight smoking-abstinent cigarette smokers received nicotine gum (4 mg) in a randomized, double-blind, placebo-controlled, crossover design. In a dichotic listening task [which required participants to attend and detect (target) deviant stimuli in one ear and to ignore similar stimuli in the other ear] which included ERP recordings and assessment of response speed and accuracy measures, nicotine gum failed to alter behavioural performance or amplitudes of ERP components sensitive to selective attention [reflected in the N100 and negative difference (Nd) component] or to pre-attentive detection of acoustic change [reflected in the mismatch negativity (MMN) component]. However, nicotine did influence the speed of these voluntary selective processes, as reflected by shortened latencies of the early Nd component. The findings are discussed in relation to the stimulus filter theory of smoking, and with respect to nicotine's actions on involuntary and controlled aspects of selective attention processes.

Nicotine improves memory for delayed intentions

RATIONALE

The present paper asked first whether the cholinergic agonist nicotine improves memory for delayed intentions (prospective memory, ProM) and second whether pharmacological dissociation would support the psychological distinction that is made between strategic (effortful) and automatic (non-effortful) intention activation in prospective memory.

OBJECTIVES

To use nicotine as a pharmacological tool with which to examine the neurochemical bases of prospective memory and to dissociate strategic from automatic components of ProM retrieval.

METHODS

In three experiments, minimally deprived (2 h) smokers either smoked or abstained prior to completing a standard prospective memory study. This involved participants in the simultaneous processing of a ProM task and a cover task (ongoing between the setting and the recall of the intention). Here, the ongoing task involved lexical decision (LDT), while the ProM task required a response to pre-specified target items occurring within the LDT stimuli. Variations in task instructions were used to manipulate the processing requirements of the ProM task, the attention allocated to the ProM task and the balance of importance assigned to the ongoing and ProM tasks.

RESULTS

In experiment 1, where the ProM processing was automatic, nicotine did not improve ProM accuracy. In experiment 2, where the ProM task involved strategic processing, positive effects of nicotine were observed. In experiment 3, we covaried ProM task instructions, assigned task importance and nicotine conditions. We observed a main effect of nicotine on ProM accuracy, a main effect of task on ProM accuracy and a main effect of assigned task importance on ProM accuracy. There were no interactions between the factors.

CONCLUSIONS

Employing both direct and indirect manipulations of strategic engagement, we demonstrated nicotine-induced enhancement of performance on the ProM task. The results are consistent with the view that relatively small changes in instruction and in task variables engage strategic processing in a ProM task and that when these conditions stretch cognitive resources, nicotine may significantly improve performance.

Neuroendocrinological and neuropsychological correlates of dopaminergic function in nicotine dependence

RATIONALE

There is multiple evidence that nicotine--as with ethanol and other drugs of abuse--stimulates dopamine release in the ventral striatum as a central part of the brain reward circuits. Chronic nicotine exposure leads to changes in these dopaminergic reward circuits. During nicotine withdrawal, an impaired dopaminergic function has been reported. On the behavioral level, this seems to result in motivational disturbances in abstaining smokers.

OBJECTIVES

To investigate the impact of smoking on dopaminergic function in humans both on a neuroendocrinological and on a neuropsychological level.

METHODS

Thirty-seven healthy smokers were assessed whilst smoking (test 1) and after abstaining overnight for 12 h (test 2). A control group of 18 non-smokers was also examined twice. Severity of nicotine dependence, incentive motivation, digit span and verbal fluency were assessed. The sensitivity of central dopamine (DA) D2 receptors was assessed with the apomorphine-induced growth hormone (GH) secretion.

RESULTS

ANOVA revealed that GH response was significantly lower in smokers than in non-smokers (P=0.04). The GH response was significantly inversely correlated with severity of nicotine dependence (r=-0.39). Neuropsychological performance was not influenced by smoking status. After overnight abstinence from nicotine GH response, digit span and verbal fluency were not affected, whereas incentive motivation was significantly impaired in smokers (P=0.04).

CONCLUSIONS

Smoking is significantly associated with a reduced sensitivity of central DA D2 receptors. This alteration of dopaminergic sensitivity is stable even after 12 h of abstinence from nicotine. Therefore, the hypothesis that the motivational impairment during withdrawal from nicotine is associated with an altered sensitivity of central DA D2 receptors cannot be supported.

Residential smoking therapy

OBJECTIVE

To evaluate a pilot 4-day residential smoking treatment program for smokers who had relapsed after participation in an outpatient smoking program.

DESIGN

A single-arm clinical trial. Participants stayed in a supportive, smoke-free environment for 4 days during which they attended educational sessions on nutrition, exercise, and psychology. Nicotine withdrawal was treated with nicotine inhalers and patches. After discharge, participants attended monthly outpatient group sessions for 6 months.

SETTING

The Durham, NC Veterans Affairs Medical Center residential unit.

PARTICIPANTS

Twenty-three medical outpatient smokers.

MEASUREMENTS

Seven-day point prevalence smoking abstinence was determined by self-report of zero cigarettes smoked and verified by exhaled carbon monoxide <8 parts per million.

MAIN RESULTS

Participants' mean age was 57.4 years; 100% were male; 61% were Caucasian; and 39% were African American. The mean score on the Fagerström Test for Nicotine Dependence was 7.1 (SD 2.3). Daily nicotine doses ranged from the nicotine inhaler alone to 56 mg of transdermal nicotine plus nicotine inhaler. Verified smoking abstinence on discharge (after 4 days) was 21/23 or 91.3% (95% confidence interval [95% CI], 73 to 100). At 6 months, the 7-day point abstinence rate was 6/23 or 26.1% (95% CI, 15 to 36).

CONCLUSIONS

This pilot residential smoking treatment program was designed to assist smokers who relapsed after outpatient treatment. Four days of residential smoking therapy successfully relieved smoking withdrawal. At 6 months after discharge, participants maintained an abstinence rate comparable to other medical therapies for smoking.

Behavioral and cognitive effects of smoking: relationship to nicotine addiction

Nicotine addiction is an extremely complex process that involves biological, psychological, behavioral, and cultural factors. Three factors that influence smoking and that are influenced by smoking are performance, stress, and body weight. We know that if nicotine-addicted smokers are deprived of nicotine, attentional and cognitive abilities can be impaired, and such deficits can be reversed if the person smokes or is given nicotine. In nonsmokers and nondeprived smokers, nicotine enhances finger tapping, focused and sustained attention, recognition memory, and reasoning. Stress results in increased smoking, but there is little empirical evidence that smoking reduces stress. Stress reduction from smoking is likely the relief of withdrawal-induced negative mood that is experienced between cigarettes. Smokers weigh on average 3-4 kg less than nonsmokers, and the weight-gain seen after quitting smoking also averages 3-4 kg. Changes in eating and energy expenditure are responsible for the body weight changes seen during smoking cessation and relapse. We need to know the full range of conditions under which nicotine affects behavior. The mechanisms by which stress functions to maintain nicotine addiction are not well understood. We do not know what interventions are effective in addressing the stress experienced during smoking cessation. Because no effective interventions have been developed to prevent weight-gain after quitting, research should focus on the concern or perception of weight-gain. We need to understand how and why body weight concerns vary across gender, age, and ethnicity because of the implications for designing effective smoking-cessation programs.

Alcohol and substance abuse

Substance abuse and dependence is a public health problem with far-reaching societal implications. The acute toxicity of substances of abuse and medical consequences of chronic use are substantial. On a more optimistic note, a great deal of progress has been made in understanding and treating substance use disorders. Expanding knowledge concerning the neurobiology of substances of abuse and substance use disorders has led to a growth in pharmacotherapeutic treatment options. A growth in understanding of behavioral processes, motivational issues, and processes of behavioral change has been important in designing new and increasingly more effective psychosocial treatments. A growing body of evidence indicates that the treatment of substance use disorders can be effective, making early diagnosis and treatment or referral increasingly important.

Effect of nicotine on brain activation during performance of a working memory task

Nicotine influences cognition and behavior, but the mechanisms by which these effects occur are unclear. By using positron emission tomography, we measured cognitive activation (increases in relative regional cerebral blood flow) during a working memory task [2-back task (2BT)] in 11 abstinent smokers and 11 ex-smokers. Assays were performed both after administration of placebo gum and 4-mg nicotine gum. Performance on the 2BT did not differ between groups in either condition, and the pattern of brain activation by the 2BT was consistent with reports in the literature. However, in the placebo condition, activation in ex-smokers predominated in the left hemisphere, whereas in smokers, it occurred in the right hemisphere. When nicotine was administered, activation was reduced in smokers but enhanced in ex-smokers. The lateralization of activation as a function of nicotine dependence suggests that chronic exposure to nicotine or withdrawal from nicotine affects cognitive strategies used to perform the memory task. Furthermore, the lack of enhancement of activation after nicotine administration in smokers likely reflects tolerance.

Moving out of the laboratory: does nicotine improve everyday attention?

The most robust demonstrations of the nicotine-related performance effects on human cognitive processes are seen in tasks that measure attention. If nicotine does have some potential for enhancing attention, the obvious question to ask is whether the effects demonstrated in the laboratory hold any significance for real-life performance. This paper describes three studies that compare the effects in smokers of a single own brand cigarette on laboratory tests of attention and on everyday analogues of these laboratory tasks. In the laboratory measures of sustained attention and in the everyday analogue, performance advantages were registered in the smoking condition. These benefits were observed in smokers who abstained for a self-determined period of not less than 2 h. The studies were unable to replicate previous research reporting positive effects of smoking on a laboratory task of selective attention, the Stroop task. Small but significant improvements in performance were registered in the everyday analogues, which involved sustaining attention in a dual task situation, a telephone directory search task and a map search task. In addition, smokers showed a significant colour-naming decrement for smoking-related stimuli in the Stroop task. This attentional bias towards smoking-related words occurred independent of whether they had abstained or recently smoked an own brand cigarette. The effect is discussed in terms of the two-component model of processing bias for emotionally valenced stimuli.

Smoking after nicotine deprivation enhances cognitive performance and decreases tobacco craving in drug abusers

This study investigated the effects of nicotine deprivation and smoking on cognitive abilities and tobacco craving. Twenty smokers with histories of drug abuse completed the Questionnaire on Smoking Urges (QSU) and two cognitive tests before and after smoking two cigarettes during two 90-min sessions. After two cigarettes were smoked at Session 1, subjects were tobacco abstinent for 18 h until Session 2 the next morning. Response time on a logical reasoning test was unchanged by tobacco deprivation and was faster after smoking on Session 2. Deprivation slowed responding on a letter search test, which was reversed by smoking to pre-deprivation baseline. Tobacco deprivation increased scores on the QSU; smoking after deprivation reduced craving scores to smoking baseline levels. These results confirmed the utility of the QSU to measure changes in craving induced by tobacco deprivation and smoking. Further, the data suggest that deprivation-induced deficits and smoking-induced enhancements in performance may be specific to certain cognitive domains.