[show abstract][hide abstract] ABSTRACT: RATIONALE: Impulsive behavior is associated with both alcohol use disorders and a family history of alcoholism (FHA). One operational definition of impulsive behavior is the stop-signal task (SST) which measures the time needed to stop a ballistic hand movement. OBJECTIVE: Employ functional magnetic resonance imaging (fMRI) to study right frontal responses to stop signals in heavy drinking subjects with and without FHA, and as a function of alcohol exposure. METHODS: Twenty-two family history-positive (FHP; age = 22.7 years, SD = 1.9) and 18 family history-negative (FHN; age = 23.7, SD = 1.8) subjects performed the SST in fMRI in two randomized visits: once during intravenous infusion of alcohol, clamped at a steady-state breath alcohol (BrAC) concentration of 60 mg/dL, and once during infusion of placebo saline. An independent reference group (n = 13, age = 23.7, SD = 1.8) was used to identify a priori right prefrontal regions activated by successful inhibition (Inh) trials, relative to "Go" trials that carried no need for inhibition [Inh > Go]. RESULTS: FHA interacted with alcohol exposure in right prefrontal cortex, where alcohol reduced [Inh > Go] activation in FHN subjects but not in FHP subjects. Within this right frontal cortical region, stop-signal reaction time also correlated negatively with [Inh > Go] activation, suggesting that the [Inh > Go] activity was related to inhibitory behavior. CONCLUSIONS: The results are consistent with the low level of response theory (Schuckit, J Stud Alcohol 55:149-158, 1980; Quinn and Fromme, Alcohol Clin Exp Res 35:1759-1770, 2011), with FHP being less sensitive to alcohol's effects.
[show abstract][hide abstract] ABSTRACT: BACKGROUND: Operant responding paradigms quantify a subject's motivation for reward, but such studies employing ingested alcohol cannot assure the same incremental increase in brain exposure to alcohol across subjects because of substantial variability in absorption kinetics. We developed a human progressive ratio (PR) paradigm using the computer-assisted self-infusion of ethanol (CASE) system that overcomes such variability and conducted a pilot study to assess its utility for detecting an interaction of subjects' GABRA2 or GABRG1 genotype and pretreatment with 1 mg of lorazepam (LZ) vs. placebo on their willingness to work for alcohol rewards. METHODS: Twenty healthy, nondependent drinkers, aged 21 to 27, were balanced on rs279871 and rs2350439 single nucleotide polymorphisms in the GABRA2 and GABRG1 genes, respectively. Subjects worked for alcohol, with water as an alternative reinforcer (AR), using a progressive schedule of a task that required constant attention and adapted to both fatigue and drug effects. Testing began 1 hour after pretreatment with 1 mg LZ or placebo in a crossover design. RESULTS: The CASE system performed well, and the constant attention task was perceived as work by all subjects. GABRA2 homozygosity did not significantly predict either breakpoint or cumulative work, whereas a significant GABRG1 genotype by LZ pretreatment interaction for cumulative work was detected (p = 0.04). Breakpoint revealed a weak trend toward pretreatment drug effects (p = 0.11), and a somewhat stronger interaction of LZ pretreatment with GABRG1 genotype (p = 0.06). GABRG1 status revealed a more complex relationship with respect to motivation for alcohol with and without LZ pretreatment; AG and GG individuals worked more for alcohol under both pretreatment conditions, while AA individuals worked more for the AR. CONCLUSIONS: The CASE PR paradigm shows promise as a laboratory method for use in drug development and phenotyping studies.
Alcoholism Clinical and Experimental Research 07/2012; · 3.42 Impact Factor
[show abstract][hide abstract] ABSTRACT: The instantaneous rate of change of alcohol exposure (slope) may contribute to changes in measures of brain function following administration of alcohol that are usually attributed to breath alcohol concentration (BrAC) acting alone. To test this proposition, a 2-session experiment was designed in which carefully prescribed, constant-slope trajectories of BrAC intersected at the same exposure level and time since the exposure began. This paper presents the methods and limitations of the experimental design.
Individualized intravenous infusion rate profiles of 6% ethanol (EtOH) that achieved the constant-slope trajectories for an individual were precomputed using a physiologically based pharmacokinetic model. Adjusting the parameters of the model allowed each infusion profile to account for the subject's EtOH distribution and elimination kinetics. Sessions were conducted in randomized order and made no use of feedback of BrAC measurements obtained during the session to modify the precalculated infusion profiles. In one session, an individual's time course of exposure, BrAC(t), was prescribed to rise at a constant rate of 6.0 mg% per minute until it reached 68 mg% and then descend at -1.0 mg% per minute; in the other, to rise at a rate of 3.0 mg% per minute. The 2 exposure trajectories were designed to intersect at a BrAC (t = 20 minutes) = 60 mg% at an experimental time of 20 minutes.
Intersection points for 54 of 61 subjects were within prescribed deviations (range of ± 3 mg% and ± 4 minutes from the nominal intersection point).
Results confirmed the feasibility of applying the novel methods for achieving the intended time courses of the BrAC, with technical problems limiting success to 90% of the individuals tested.
Alcoholism Clinical and Experimental Research 04/2012; 36(6):1042-9. · 3.42 Impact Factor
[show abstract][hide abstract] ABSTRACT: Antisocial traits are common among alcoholics- particularly in certain subtypes. Although people with antisocial tendencies show atypical brain activation in some emotion and reward paradigms, how the brain reward systems of heavy drinkers (HD) are influenced by antisocial traits remains unclear. We used subjects' preferred alcohol drink odors (AO), appetitive (ApCO) and non-appetitive (NApO) control odors in functional magnetic resonance imaging (fMRI) to determine if reward system responses varied as a function of antisocial trait density (ASD). In this retrospective analysis, we examined 30 HD who had participated in imaging twice: once while exposed to clamped intravenous alcohol infusion targeted to 50mg%, and once during placebo saline infusion. Under placebo, there were positive correlations between ASD and blood oxygenation level dependent (BOLD) activation in the [AO>ApCO] contrast in the left dorsal putamen, while negative correlations were present in medial orbitofrontal cortex (OFC) and the bilateral amygdala. A similar pattern was observed in the correlation with the [AO>NApO] contrast. This inverse relationship between ASD and activation in OFC and amygdala was specific to AO. However, negative correlations between ASD and the [ApCO>NApO] contrast were also present in the insula, putamen, and medial frontal cortex. These data suggest that frontal and limbic reward circuits of those with significant ASD are less responsive to reward cues in general, and particularly to alcohol cues in medial OFC and amygdala. These findings are broadly consistent with the reward deficiency syndrome hypothesis, although positive correlation in the striatum suggests regional variability.
[show abstract][hide abstract] ABSTRACT: In studies where [(11)C]raclopride (RAC) positron emission tomography (PET) is used to assess changes in striatal dopamine, it is important to control for cognitive states, such as drug craving, that could alter dopamine levels. In cigarette smokers, transdermal nicotine patches (TNP) can control nicotine craving, but the effects of nicotine patches on RAC binding are unknown. Thus, we sought to determine the test-retest reliability of RAC binding in the presence of nicotine patches.
Eleven male smokers were scanned twice with RAC on separate days while wearing TNP.
Across the striatum, test-retest variability was 7.63 ± 5.88; percent change in binding potential was 1.11 ± 9.83; and the intraclass correlation coefficient was 0.91 (p < 0.0001).
Baseline RAC binding is highly reproducible in smokers wearing nicotine patches. This suggests that TNP are an acceptable method for controlling cigarette craving during studies that utilize RAC to examine changes in dopamine.
European Journal of Nuclear Medicine 02/2012; 39(2):220-5. · 4.53 Impact Factor
[show abstract][hide abstract] ABSTRACT: Individuals learn associations between alcohol's sensory properties and intoxication, with such conditioned stimuli (CS) becoming involved in craving and relapse. However, these CS also carry idiosyncratic associations.
This study aimed to test brain responses to novel CS conditioned with alcohol intoxication.
Fourteen heavy drinkers (age 24.9 ± 3.2) performed a reaction time task with embedded novel geometric CS and were told only that the task was to measure alcohol's effect on speed. Rapid intravenous alcohol infusion (the unconditioned stimulus; UCS) began with the appearance of a CS+, using pharmacokinetic modeling to increment breath alcohol by ~18 mg% in 200 s per each of six CS-UCS pairings. Placebo-saline infusion with CS- used the same infusion parameters in same-day randomized/counterbalanced sessions. The next morning subjects, connected to inactive intravenous pumps, underwent functional magnetic resonance imaging (fMRI) of the same task with mixed brief presentations of CS+, CS-, and irrelevant CS and were told that alcohol could be infused at any time during imaging.
CS- responses were significantly greater than those of CS+ in medial frontal cortex. Notably, CS+ responses were negative, suggesting reduced neural activity. Negative activity was most pronounced in early scans, extinguishing with time. As subjects were told that alcohol could be administered in fMRI, a CS+ without alcohol is similar to a negative prediction error, with associated reduced frontal activity during withheld reward.
Novel stimuli relatively free of demand characteristics can be classically conditioned to intermittent brain exposure of even low alcohol concentrations, permitting imaging studies of conditioned alcohol expectancies.
[show abstract][hide abstract] ABSTRACT: The differentiator model predicts that individuals with a positive family history of alcoholism (FHA) or heavy alcohol consumers will feel more sensitive to the effects of alcohol on the ascending phase of the blood alcohol content while feeling less sedated on the descending phase. This study tested whether subjective perceptions are sensitive to the slope of breath alcohol concentration (BrAC) and whether that sensitivity is associated with an FHA and/or recent drinking history (RDH).
Family-history-positive (FHP, n = 27) and family-history-negative (FHN, n = 27) young adult nondependent drinkers were infused intravenously with alcohol in 2 sessions separated by 1 week. After 20 minutes, one session had an ascending BrAC (+3.0 mg%/min), while the other session had a descending BrAC (-1 mg%/min). The BrAC for both sessions at this point was approximately 60 mg%, referred to as the crossover point. Subjective perceptions of intoxication, high, stimulated, and sedation were sampled frequently and then interpolated to the crossover point. Within-subject differences between ascending and descending responses were examined for associations with FHA and/or RDH.
Recent moderate drinkers reported increased perceptions of feeling intoxicated (p < 0.023) and high (p < 0.023) on the ascending slope compared with the descending slope. In contrast, recent light drinkers felt more intoxicated and high on the descending slope.
Subjective perceptions in young adult social drinkers depend on the slope of the BrAC when examined in association with RDH. These results support the differentiator model hypothesis concerning the ascending slope and suggest that moderate alcohol consumers could be at risk for increased alcohol consumption because they feel more intoxicated and high on the ascending slope. Subjects did not feel less sedated on the descending slope, contrary to the differentiator model but replicating several previous studies.
Alcoholism Clinical and Experimental Research 09/2011; 36(6):1050-7. · 3.42 Impact Factor
[show abstract][hide abstract] ABSTRACT: The influence of family history and genetics on the risk for the development of abuse or dependence is a major theme in alcoholism research. Recent research have used endophenotypes and behavioral paradigms to help detect further genetic contributions to this disease. Electronic tasks, essentially video games, which provide alcohol as a reward in controlled environments and with specified exposures have been developed to explore some of the behavioral and subjective characteristics of individuals with or at risk for alcohol substance use disorders. A generative model (containing parameters with unknown values) of a simple game involving a progressive work paradigm is described along with the associated point process signal processing that allows system identification of the model. The system is demonstrated on human subject data. The same human subject completing the task under different circumstances, e.g., with larger and smaller alcohol reward values, is assigned different parameter values. Potential meanings of the different parameter values are described.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:2699-702.
[show abstract][hide abstract] ABSTRACT: This review focuses on 27 studies employing experimental alcohol self-administration (ASA) in humans which were published between 1989 and 2010. Twelve studies enrolling healthy, non-dependent social drinkers (HSD) were aimed at evaluating physiological and behavioral determinants of alcohol-induced reward or modeling situations of increased risk to develop alcohol use disorders. The remaining 15 studies tested the effect of medications such as naltrexone, nalmefene, nicotine, mecamylamine, varenicline, gabapentin, aripiprazole, and rimonabant on ASA. The participants were either HSD or non-treatment-seeking alcoholics (NTSA). In 25 of these studies, the subjects ingested alcohol orally and reached a mean peak blood alcohol concentration (BAC) during baseline conditions between 43 and 47 mg% (0.043-0.047%). Two recent studies employed computer-assisted self-infusion of ethanol (CASE), where subjects press a button to request multiple sequential alcohol exposures intravenously instead of drinking. This method has been demonstrated to be safe and provides increased experimental control of BAC and keeps subjects blind concerning the amount already self-administered. Peak exposures in the CASE studies ranged from 60 to 80 mg% in HSD and up to 240 mg% in NTSA.
Current topics in behavioral neurosciences. 07/2011; 13:315-53.
[show abstract][hide abstract] ABSTRACT: Recent research on alcoholism explores the influence of family history and genetics on the risk of developing abuse or dependence. Endophenotypes and behavioral paradigms have been used to help detect genetic contributions to this disease. Electronic tasks, which can be considered video games, that provide alcohol as a reward in controlled environments have been developed to explore some of the behaviors and characteristics of individuals with or at risk for alcohol substance use disorders. One such game involves a progressive work paradigm where subjects receive larger or smaller alcohol rewards for completing the task. A generative model for this game is described along with the signal processing needed to characterize the subjects' behavior by system identification. Statistical performance of the algorithm is described and evaluated for the human data. Potential meanings of the different parameter values and the performance results are described.
[show abstract][hide abstract] ABSTRACT: Significant evidence has accumulated to suggest an association between single-nucleotide polymorphisms (SNPs) in the GABRA2 gene and alcoholism. However, research has yet to show an association between these polymorphisms and the human brain's reward system function. In this study, we stratified subjects who had participated in an fMRI study of alcohol cue responses according to their genotype at a SNP in GABRA2 (rs279871) shown to be associated with alcohol dependence (Edenberg et al., 2004).
Genotyping showed 13 subjects to be homozygous for the high-risk allele (AA), and 23 subjects to be heterozygous (AG). In fMRI, subjects were exposed to the aromas of their preferred alcoholic drink odors (AO), as well as to appetitive control odors (ApCO) under both alcohol intoxication and placebo control conditions.
Homozygous AA subjects had a larger [AO > ApCO] response than did AG subjects in medial frontal cortical areas thought to code reward value. However, AG subjects had a larger [AO > ApCO] effect in the ventral tegmental area. Alcohol intoxication did not alter these group differences.
These are the first data to suggest that GABRA2 genotype could affect the brain's responses to cues associated with alcohol.
Alcoholism Clinical and Experimental Research 12/2010; 34(12):2169-78. · 3.42 Impact Factor
[show abstract][hide abstract] ABSTRACT: Obesity, smoking, and conduct problems have all been associated with decrements in brain function. However, their additive and interactive effects have rarely been examined. To address the deficiency, we studied P300a and P300b electroencephalographic potentials in 218 women grouped by the presence versus absence of: (1) a BMI > or = 30 kg/m(2); (2) recent smoking; and (3) > or = 2 childhood conduct problems. Analyses revealed smaller P300a and P300b amplitudes over the posterior scalp among recent smokers versus nonsmokers. No corresponding group differences were found in P300 latencies or frontal scalp amplitudes. The most interesting analysis result was an interaction between conduct problems and obesity limited to the frontally generated P300a component: its latency was significantly greater in women with both attributes than in those with either or neither attribute. An exploratory ANOVA, substituting the genotype of a GABRA2 SNP for conduct problems, also demonstrated an interaction with obesity affecting P300a latency. It is hypothesized that conduct problems, and a conduct-problem-associated GABRA2 genotype, decrease the age-of-onset and/or increase the lifetime duration of obesity. As a result, they may potentiate the adverse effects of obesity on frontal white matter and thereby increase P300a latency. Smoking may affect brain function by a different mechanism to reduce posterior scalp P300a and P300b amplitudes while preserving frontal scalp P300a latency and amplitude.
American Journal on Addictions 01/2010; 19(5):391-400. · 1.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: Although a family history of alcoholism is the strongest risk factor for developing alcohol dependence, there are few studies of the association between familial alcoholism and the human brain's reward system activity. We used functional magnetic resonance imaging (fMRI) to determine how family history affects the brain's response to subjects' preferred alcoholic drink odors (AO) as compared to appetitive control odors (ApCO). Fourteen non-dependent heavy drinkers (HD) who were family history positive (FHP) participated, as did 12 HD who were family history negative (FHN). Subjects were imaged under both alcohol intoxication and placebo, using intravenous infusion and pharmacokinetic modeling to target a blood alcohol level of 50 mg%. Under placebo, HD-FHP had a larger medial frontal [AO>ApCO] effect than did HD-FHN. Alcohol intoxication dampened this response in the HD-FHP but potentiated it in the HD-FHN. This suggests that a family history of alcoholism and brain exposure to alcohol interact in heavy drinkers to differentially affect how the brain responds to alcohol cues.
[show abstract][hide abstract] ABSTRACT: While there is extensive literature on the relationship between the P3 component of event-related potentials (ERPs) and risk for alcoholism, there are few published studies regarding other potentially important ERP components. One important candidate is the N4(00) component in the context of semantic processing, as abnormalities in this component have been reported for adult alcoholics.
A semantic priming task was administered to nonalcohol dependent male offspring (18 to 25 years) of alcoholic fathers [high risk (HR) n = 23] and nonalcoholic fathers [low risk (LR) n = 28] to study whether the 2 groups differ in terms of the N4 component. Subjects were presented with 150 words and 150 nonwords. Among the words, 50 words (primed) were preceded by their antonyms (prime, n = 50), whereas the remaining 50 words were unprimed. For the analysis, N4 amplitude and latency as well as behavioral measures for the primed and unprimed words were considered.
A significant interaction effect was observed between semantic condition and group, where HR subjects did not show N4 attenuation for primed stimuli.
The lack of N4 attenuation to primed stimuli and/or inability to differentiate between primed and unprimed stimuli, without latency and reaction time being affected, suggest deficits in semantic priming, especially in semantic expectancy and/or postlexical semantic processing in HR male offspring. Further, it indicates that it might be an electrophysiological endophenotype that reflects genetic vulnerability to develop alcoholism.
Alcoholism Clinical and Experimental Research 09/2009; 33(12):2027-36. · 3.42 Impact Factor
[show abstract][hide abstract] ABSTRACT: Our previous studies have used intravenous (IV) clamping methods to demonstrate that family history positive (FHP) subjects exhibit a greater initial response to alcohol than family history negative (FHN) subjects. These results differ from other studies of family history of alcoholism (FHA) influences, most of which have used an oral alcohol challenge, suggesting that the route of administration may influence both the response to alcohol and FHA-related differences in response. To examine this possibility, one approach would be to directly compare responses following oral and IV alcohol administration in the same subjects. There is, however, a 3- to 4-fold variance, between- and within-subjects, in the breath alcohol concentrations (BrACs) following oral alcohol administration. Thus, our objective was to characterize the between-subject variability in the time course of BrACs following oral alcohol administration in healthy volunteers and to develop an IV infusion method to mimic the BrAC-time course attained following oral alcohol in the same subject.
This was a 2-session study in young adult, healthy, nondependent drinkers. In the first session, subjects ingested an oral dose of alcohol, based on total body water, to achieve a target peak BrAC of 80 mg%. In the second session, subjects received an IV infusion of ethanol designed to achieve the same BrAC time course as that achieved in the first session. The individualized infusion-rate profile was precomputed using a physiologically-based pharmacokinetic (PBPK) model for alcohol with model parameters adjusted to the individual's physiology. The peak BrACs (C(max)), times of peak BrAC (T(max)), and the areas under the BrAC vs. time curve (AUC) were compared between sessions to assess how closely the BrAC exposure during the IV infusion session mimicked the exposure following oral alcohol.
The time course of BrACs following oral alcohol administration showed a high degree of between-subject variability. Mean C(max), T(max), and AUC did not differ by gender, indicating that calculation of oral doses based on total body water results in comparable BrAC-time courses, on average, for females and males. The IV infusion driven BrAC-time profiles demonstrated good fidelity to the BrAC-time curves resulting from oral alcohol: the mean %difference in C(max) and AUC were both 11%, while the mean %difference for T(max) was 27%. This degree of variability is less than half that seen across individuals following oral alcohol administration, which was substantial [coefficient of variation (%CV) ranging from 22 to 52%].
Despite the use of standardized doses and controlled experimental conditions, there was substantial between-subject variability in the BrAC time course following oral administration of alcohol. The PBPK-model-based infusion method can mimic the BrACs attained with oral alcohol for individual subjects. This method provides a platform to evaluate effects attributable to the route of administration on the response to alcohol, as well as the influence of determinants such as family history of alcoholism on the alcohol response.
Alcoholism Clinical and Experimental Research 04/2009; 33(5):938-44. · 3.42 Impact Factor
[show abstract][hide abstract] ABSTRACT: Physiologically based pharmacokinetic models have been used to describe the distribution and elimination of ethanol after intravenous administration. These models have been used to estimate the ethanol infusion profile that is sufficient for achieving a prescribed breath ethanol concentration time course in individuals, providing a useful platform for several pharmacokinetic and pharmacodynamic investigations. Mathematical foundations of these models are examined, including the derivation of an explicit set of governing equations in the form of a system of nonlinear ordinary differential equations. These equations can then be used to formulate and refine parameter identification and control strategies. Finally, a framework in which models related to this model can be constructed and analyzed is described.
IEEE Transactions on Biomedical Engineering 01/2009; · 2.35 Impact Factor
[show abstract][hide abstract] ABSTRACT: Acute alcohol effects may differ in social drinkers with a positive family history of alcohol use disorders (FHP) compared to FH negative (FHN) controls.
To investigate whether FHP subjects prefer higher levels of brain alcohol exposure than do FHN controls.
Twenty-two young healthy nondependent social drinkers participated in two identical sessions of computer-assisted self-infusion of ethanol (CASE); the first for practicing the procedures, the second to test hypotheses. All 12 FHP (four women) and ten FHN (three women) participants received a priming exposure, increasing arterial blood alcohol concentration (aBAC) to 30 mg% at 10 min and decreasing it to 15 mg% at 25 min. A 2-h self-administration period followed, during which only the subjects could increase their aBAC by pressing a button connected to a computer controlling the infusion pump. Infusion rate profiles were calculated instantaneously to increase aBAC by precisely 7.5 mg% within 2.5 min after each button press, followed by a steady descent. Subjects were instructed to produce the same alcohol effects as they would do at a weekend party.
The mean and maximum aBAC during the self-administration period and the number of alcohol requests (NOAR) were significantly higher in the FHP vs. FHN participants.
This is the first laboratory experiment demonstrating higher alcohol self-administration in FHP compared to FHN subjects. A practice session increases the sensitivity of CASE experiments for detection of subtle differences in human alcohol self-administration.