Intraindividual variability in brain activation-A novel correlate of obesity risk among female college students

There are published data describing impairments in the brain function of adolescents or young adults who have a genetic or familial predisposition for obesity. From these descriptions, it is often assumed that the impairments are appropriately captured by a central tendency estimate and therefore consistently detectable. The present study questions this assumption and shows that the variability in brain function over the time course of a cognitive task is a better predictor of familial risk than its central tendency. Sixty-nine female young adults lacking an obese parent and 24 female young adults with an obese parent were compared on the average amplitude and inter-trial variability (ITV) in amplitude of their P300 electroencephalographic responses to rarely-occurring stimuli during a selective attention task. Simple group comparisons revealed statistically significant findings with effect sizes that were markedly greater for analyses of P300 ITV versus P300 average amplitude. It is suggested that the elevation in P300 ITV among young adults with familial risk indicates temporal instability in systems responsible for the maintenance of attention. These fluctuations may episodically disrupt their attention to satiety cues as well as other cues that influence behavior regulation.

Altered brain activation in uncomplicated pediatric obesity: The second moment is more sensitive than the first

Traditionally, studies of the neurocognitive correlates of obesity have computed a central tendency across trials of a task to estimate the functional abilities of individual members of obese and non-obese groups. This computation assumes that the correlate is stable over time-a questionable assumption when individuals are impulsive, periodically inattentive, and capable of overcompensation following awareness of failure. The present investigation departs from the tradition by focusing on the second moment, or variability, in brain activation during a simple selective attention task. It compared 124 non-obese and 80 obese teenaged girls on the across-trial average amplitude and inter-trial variability (ITV) of a sensitive biomarker of attention, the P300 event-related electroencephalographic potential. It found that P300 ITV outperformed P300 average amplitude in differentiating the groups. Further, it found that the elevated P300 ITV among obese teenagers was associated with other indicators of impulsivity and inattention as well as slower reaction times and a trend toward more variable reaction times. Future studies should investigate the value of P300 ITV as an objective and sensitive endpoint for cognitive training focused on improving the attention skills of obese children.

Signal in the noise: Altered brain activation among adolescent alcohol users detected via the analysis of intra-individual variability1

RATIONALE

Unlike its average level, the variability in brain activation over time or trials can capture subtle and brief disruptions likely to occur among participants with low-to-moderate levels of substance use or misuse.

OBJECTIVE

The present study used this intra-individual variability measurement approach to detect neural processing differences associated with light-to-moderate use of alcohol among 14-19-year-old adolescents.

METHOD

A total of 128 participants reporting any level of alcohol use during the previous 6 months and 87 participants reporting no use during this period completed intake questionnaires and interviews as well as an assessment of P300 electroencephalographic responses to novel stimuli recorded during two separate tasks.

RESULTS

In addition to differing in recent alcohol use, the groups differed in nicotine and cannabis use, risk-taking behavior and conduct disorder symptoms, and P300 amplitude inter-trial variability (ITV) across both tasks. Across all participants, P300 ITV was positively correlated with a family history of depression but not with a family history of alcohol dependence. There were no group differences in P300 amplitude averaged across trials.

CONCLUSIONS

Recent reports attributing brain volume or brain function differences to an effect of light-to-moderate alcohol use should be viewed with great caution. In the present analysis of brain function differences among substance-using adolescents, the group differences were small, complicated by many factors coinciding with or preceding alcohol use, and not reflected in a stable central tendency.

Inter-trial variability in postural control and brain activation: Effects of previous opiate abuse

There is an abundant literature demonstrating the superiority of inter-trial variability (ITV) of reaction time over mean reaction time in the early identification of subtle cognitive processing decrements. The present study extends these ideas by examining brain activation and postural control ITV among participants with versus without a history of chronic opiate abuse. Participants enrolled in opiate abuse (n = 82) and control (n = 112) groups completed tasks that challenged selective attention and balance. During the respective tasks, the inter-trial variabilities in frontal P300a electroencephalographic responses and sway strategy scores outperformed their mean levels in differentiating the groups. The relevance of several potential alternative explanations for the differences, including premorbid conduct disorder and comorbid alcohol abuse, depression, and methadone use, was discounted via simultaneous or post hoc analyses. It appears that chronic opiate abuse has adverse CNS effects that persist into the protracted abstinence period. These effects alter the temporal stability of its response to external and internal stimuli.

Temporal instability in brain activation: a novel paradigm for evaluating the maintenance of attention among substance dependent patients

RATIONALE

Prior studies have demonstrated statistically significant but subtle differences in brain function between patients with a history of substance dependence (SD) and control groups.

OBJECTIVES

The goal of the present study was to show that variability in brain activation over the trials of a cognitive task is more useful for revealing the putative impact of SD than analyses focusing on the amplitude of activation averaged over trials. The study also tested the additional contribution of antisocial personality disorder (ASPD)-a prevalent comorbidity that promotes both an early onset and more severe course of SD.

METHODS

Two hundred eleven adults performed two selective attention tasks while P300 event-related electroencephalographic potentials were recorded. They were assigned to one of 3 mutually exclusive groups: no lifetime history of SD or ASPD (n = 67), a SD history but no ASPD (n = 68), or both SD and ASPD (n = 76).

RESULTS

The major finding was a statistically significant elevation of P300 amplitude inter-trial variability (ITV) in the SD plus ASPD group in comparison to the group with neither attribute. The elevation was detected during both selective attention tasks and most prominent at electrodes sites located over the frontal brain. There were no group differences in P300 amplitude averaged over trials.

CONCLUSIONS

We conclude from these findings that the ITV of P300 amplitude is an efficient and sensitive biomarker of the maintenance of attention. It is valuable for revealing group differences associated with substance dependence and ASPD. It may ultimately be valuable for detecting improvements resulting from psychostimulant treatment or other interventions, including cognitive remediation.

Neural Responses to Signals for Behavior Change: Greater Within-Person Variability is Associated With Risk Factors for Substance Dependence

BACKGROUND

An impaired ability to change behavior in the face of cues indicating a need for change is one means of defining risk for substance dependence. The present study used a cognitive task administered in a laboratory as a model of this process. It focused on 2 known and related correlates of risk (conduct disorder, borderline personality disorder) and examined their associations with reactivity to cues requesting a change in motor behavior.

METHODS

A total of 224 teenagers, 14 to 19 years of age, performed a task during which white noise bursts were used to cue a requirement to reverse the mapping of right and left key press responses onto high- and low-frequency pure tones during a subsequent trial block. The amplitude of the P300 electroencephalographic (EEG) response to each cue was summarized by calculating its across-trial average as well as its intertrial variability (ITV). In addition, the number of motor response reversal failures (perseveration errors) was calculated.

RESULTS

The ITV of the P300 response to cues for behavior change was superior to its average amplitude in revealing associations with risk: It was significantly greater among teenagers with more conduct problems and more borderline personality disorder symptoms in comparison with their less-affected peers. ITV was also positively correlated with perseveration errors. No group differences were found in P300 amplitude averaged over trials.

CONCLUSIONS

The findings suggest that the measurement of intertrial variability in brain activity may be more valuable than the average level for revealing neurophysiological differences associated with impulsivity and personality risk factors for dependence. EEG measures may be particularly valuable in this context because they offer superior temporal resolution and signal-to-noise characteristics.

GRM8 genotype is associated with externalizing disorders and greater inter-trial variability in brain activation during a response inhibition task

OBJECTIVE

The present investigation tested the association of a novel measure of brain activation recorded during a simple motor inhibition task with a GRM8 genetic locus implicated in risk for substance dependence.

METHODS

122 European-American adults were genotyped at rs1361995 and evaluated against DSM-IV criteria for Alcohol Dependence, Cocaine Dependence, Conduct Disorder, and Antisocial Personality Disorder. Also, their brain activity was recorded in response to rare, so-called "No-Go" stimuli presented during a continuous performance test. Brain activity was quantified with two indices: (1) the amplitude of the No-Go P300 electroencephalographic response averaged across trials; and (2) the inter-trial variability of the response.

RESULTS

The absence of the minor allele at the candidate locus was associated with all of the evaluated diagnoses. In comparison to minor allele carriers, major allele homozygotes also demonstrated increased inter-trial variability in No-Go P300 response amplitude but no difference in average amplitude.

CONCLUSIONS

GRM8 genotype is associated with Alcohol and Cocaine Dependence as well as personality risk factors for dependence. The association may be mediated through an inherited instability in brain function that affects cognitive control.

SIGNIFICANCE

The present study focuses on a metric and brain mechanism not typically considered or theorized in studies of patients with substance use disorders.

HIV/AIDS and an overweight body mass are associated with excessive intra-individual variability in response preparation

Factors other than HIV/AIDS may influence the cognitive function of patients living with this disease. The present study tested the influence of a common comorbid problem-an overweight body mass. It also examined intra-task variabilities in performance and brain activation as potentially more sensitive indicators of dysfunction than their mean levels. One-hundred seventy-eight participants were recruited and categorized by HIV-1 serostatus (-/+) and body mass (BMI < 26/≥ 26 kg/m²). They performed a simple time estimation task during which response time accuracy and electroencephalographic readiness potentials were recorded. A few hours later, they completed a battery of tests measuring balance and gait. The analyses revealed an advantage of variability over the mean in differentiating groups: the presence of HIV-1 and an overweight body mass were independently and additively associated with greater variability across trials in readiness potential amplitude and response accuracy. The analysis also showed that intra-task variability in the readiness potential, but not in response accuracy, was predictive of decrements in single and tandem leg balance and gait velocity. The present findings suggest that an elevated body mass is associated with, and may contribute to, problems in brain function and motor behavior experienced by patients in the current era. The findings recommend a careful consideration of the manner in which these problems are measured. When the problems are episodic and subtle, measures of central tendency may be less than ideal.

Effects of Antisocial Personality, Cocaine and Opioid Dependence, and Gender on Eye Movement Control

Substance-dependent patients have been reported to exhibit abnormal smooth pursuit and saccadic eye movements. However, contrasts of the effects of different substances and the effects of comorbid psychiatric symptoms such as antisocial personality have rarely been performed. Separate analyses examined the effects of cocaine dependence, opioid dependence, or antisocial personality disorder. In each analysis, sex was included as an additional grouping factor. The dependent measures were the gain of smooth pursuit eye movement and the delay and accuracy of saccadic eye movement. Analyses of covariance indicated that both cocaine dependence and antisocial personality, but not opiate dependence, were associated with a significant reduction in gain of smooth pursuit eye movement. Cocaine dependence and antisocial personality also slowed the onset of saccadic eye movements, but only in men. No group differences were found in the accuracy of saccadic eye movements. The results suggest that the neurophysiological effects of cocaine dependence and antisocial personality overshadow the effects of heroin. The significance of these findings for visual attention and reading skill has yet to be assessed.

Challenges in the Detection of Working Memory and Attention Decrements among Overweight Adolescent Girls

BACKGROUND

The present study is unique in employing unusually difficult attention and working memory tasks to reveal subtle cognitive decrements among overweight/obese adolescents. It evaluated novel measures of background electroencephalographic (EEG) activity during one of the tasks and tested correlations of these and other measures with psychological and psychiatric predictors of obesity maintenance or progression.

METHODS

Working memory and sustained attention tasks were presented to 158 female adolescents who were rated on dichotomous (body mass index percentile <85 vs. ≥85) and continuous (triceps skinfold thickness) measures of adiposity.

RESULTS

The results revealed a significant association between excess adiposity and performance errors during the working memory task. During the sustained attention task, overweight/obese adolescents exhibited more EEG frontal beta power as well as greater intraindividual variability in reaction time and beta power across task periods than their normal-weight peers. Secondary analyses showed that frontal beta power during the sustained attention task was positively correlated with anxiety, panic, borderline personality features, drug abuse, and loss of control over food intake.

CONCLUSIONS

The findings suggest that working memory and sustained attention decrements do exist among overweight/obese adolescent girls. The reliable detection of the decrements may depend on the difficulty of the tasks as well as the manner in which performance and brain activity are measured. Future studies should examine the relevance of these decrements to dietary education efforts and treatment response.

Deficient Event-Related Theta Oscillations in Individuals at Risk for Alcoholism: A Study of Reward Processing and Impulsivity Features

BACKGROUND

Individuals at high risk to develop alcoholism often manifest neurocognitive deficits as well as increased impulsivity. Event-related oscillations (EROs) have been used to effectively measure brain (dys)function during cognitive tasks in individuals with alcoholism and related disorders and in those at risk to develop these disorders. The current study examines ERO theta power during reward processing as well as impulsivity in adolescent and young adult subjects at high risk for alcoholism.

METHODS

EROs were recorded during a monetary gambling task (MGT) in 12-25 years old participants (N = 1821; males = 48%) from high risk alcoholic families (HR, N = 1534) and comparison low risk community families (LR, N = 287) from the Collaborative Study on the Genetics of Alcoholism (COGA). Impulsivity scores and prevalence of externalizing diagnoses were also compared between LR and HR groups.

RESULTS

HR offspring showed lower theta power and decreased current source density (CSD) activity than LR offspring during loss and gain conditions. Younger males had higher theta power than younger females in both groups, while the older HR females showed more theta power than older HR males. Younger subjects showed higher theta power than older subjects in each comparison. Differences in topography (i.e., frontalization) between groups were also observed. Further, HR subjects across gender had higher impulsivity scores and increased prevalence of externalizing disorders compared to LR subjects.

CONCLUSIONS

As theta power during reward processing is found to be lower not only in alcoholics, but also in HR subjects, it is proposed that reduced reward-related theta power, in addition to impulsivity and externalizing features, may be related in a predisposition to develop alcoholism and related disorders.

Reward processing deficits and impulsivity in high-risk offspring of alcoholics: A study of event-related potentials during a monetary gambling task

BACKGROUND

Individuals at high risk to develop alcoholism often manifest neurocognitive deficits as well as increased impulsivity. The goal of the present study is to elucidate reward processing deficits, externalizing disorders, and impulsivity as elicited by electrophysiological, clinical and behavioral measures in subjects at high risk for alcoholism from families densely affected by alcoholism in the context of brain maturation across age groups and gender.

METHODS

Event-related potentials (ERPs) and current source density (CSD) during a monetary gambling task (MGT) were measured in 12-25 year old offspring (N=1864) of families in the Collaborative Study on the Genetics of Alcoholism (COGA) Prospective study; the high risk (HR, N=1569) subjects were from families densely affected with alcoholism and the low risk (LR, N=295) subjects were from community families. Externalizing disorders and impulsivity scores were also compared between LR and HR groups.

RESULTS

HR offspring from older (16-25 years) male and younger (12-15 years) female subgroups showed lower P3 amplitude than LR subjects. The amplitude decrement was most prominent in HR males during the loss condition. Overall, P3 amplitude increase at anterior sites and decrease at posterior areas were seen in older compared to younger subjects, suggesting frontalization during brain maturation. The HR subgroups also exhibited hypofrontality manifested as weaker CSD activity during both loss and gain conditions at frontal regions. Further, the HR subjects had higher impulsivity scores and increased prevalence of externalizing disorders. P3 amplitudes during the gain condition were negatively correlated with impulsivity scores.

CONCLUSIONS

Older male and younger female HR offspring, compared to their LR counterparts, manifested reward processing deficits as indexed by lower P3 amplitude and weaker CSD activity, along with higher prevalence of externalizing disorders and higher impulsivity scores.

SIGNIFICANCE

Reward related P3 is a valuable measure reflecting neurocognitive dysfunction in subjects at risk for alcoholism, as well as to characterize reward processing and brain maturation across gender and age group.

Visual illusions and inattention: Their association with adiposity among adolescent girls

The Delboeuf concentric circle illusion is frequently invoked as an explanation for the hypothesized association between dinner plate size and overeating. We examined its association with adiposity among 162 girls, aged 14-18 years. We also examined the association of adiposity with neural and behavioral responses during a separate visual discrimination task. The analysis showed that girls with a body mass index percentile ≥ 85, or with greater triceps skinfold thickness, exhibited less sensitivity to the Delboeuf illusion than girls with normal adiposity. The excess adiposity group also exhibited significantly smaller electroencephalographic responses and more errors during the separate visual discrimination task. In combination, the findings from the two tasks suggest that girls with an elevated body mass are less sensitive to visual cues in their environment. The implications of these findings for weight loss education should be considered.

Who gains? Genetic and neurophysiological correlates of BMI gain upon college entry in women

The present investigation examined P3 event-related electroencephalographic potentials and a short and selected list of addiction-related candidate gene single nucleotide polymorphisms (SNPs) within 84 female students, aged 18-20 yrs. The students were assigned to groups defined by the presence versus absence of a positive body mass index (BMI) change from the pre-college physical exam to the current day. Analyses revealed significantly greater P3 latencies and reduced P3 amplitudes during a response inhibition task among students who exhibited a BMI gain. BMI gain was also significantly associated with a ANKK1 SNP previously implicated in substance dependence risk. In logistic regression analyses, P3 latencies at the frontal electrode and this ANKK1 genotype correctly classified 71.1% of the students into the BMI groups. The present findings suggest that heritable indicators of impaired response inhibition can differentiate students who may be on a path toward an overweight or obese body mass.

On the association of common and rare genetic variation influencing body mass index: a combined SNP and CNV analysis

Background

As the architecture of complex traits incorporates a widening spectrum of genetic variation, analyses integrating common and rare variation are needed. Body mass index (BMI) represents a model trait, since common variation shows robust association but accounts for a fraction of the heritability. A combined analysis of single nucleotide polymorphisms (SNP) and copy number variation (CNV) was performed using 1850 European and 498 African-Americans from the Study of Addiction: Genetics and Environment. Genetic risk sum scores (GRSS) were constructed using 32 BMI-validated SNPs and aggregate-risk methods were compared: count versus weighted and proxy versus imputation.

Results

The weighted SNP-GRSS constructed from imputed probabilities of risk alleles performed best and was highly associated with BMI (p = 4.3×10⁻¹⁶) accounting for 3% of the phenotypic variance. In addition to BMI-validated SNPs, common and rare BMI/obesity-associated CNVs were identified from the literature. Of the 84 CNVs previously reported, only 21-kilobase deletions on 16p12.3 showed evidence for association with BMI (p = 0.003, frequency = 16.9%), with two CNVs nominally associated with class II obesity, 1p36.1 duplications (OR = 3.1, p = 0.009, frequency 1.2%) and 5q13.2 deletions (OR = 1.5, p = 0.048, frequency 7.7%). All other CNVs, individually and in aggregate, were not associated with BMI or obesity. The combined model, including covariates, SNP-GRSS, and 16p12.3 deletion accounted for 11.5% of phenotypic variance in BMI (3.2% from genetic effects). Models significantly predicted obesity classification with maximum discriminative ability for morbid-obesity (p = 3.15×10⁻¹⁸).

Conclusion

Results show that incorporating validated effect sizes and allelic probabilities improve prediction algorithms. Although rare-CNVs did not account for significant phenotypic variation, results provide a framework for integrated analyses.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-368) contains supplementary material, which is available to authorized users.

Neural and genetic correlates of binge drinking among college women

Ninety-seven female students were assigned to groups consisting of 55 infrequent and 42 frequent binge drinkers. The groups were compared on self-report measures of impulsivity, sensation seeking, and alexithymia, as well as several measures relevant to neural and genetic mechanisms, such as brain activation during a time estimation task and selected genotypes. Analyses of stimulus-locked brain activity revealed a slow cortical potential over the right parietal cortex during time estimation that was more negative among frequent binge drinkers. This group also showed a greater prevalence of a CHRM2 genotype previously associated with substance dependence and Major Depressive Disorder as well as a modest elevation on a non-planning impulsiveness scale. We conclude that the enhanced brain activation shown by binge drinkers compensates for an underlying deficit. That deficit may be reflected in poor planning skills and a genetic difference indicating increased risk for problems in later life.

GABRA2 genotype, impulsivity, and body mass

BACKGROUND

The goal of this study was to test a hypothesis associating impulsivity with an elevated body mass index (BMI).

METHODS

To this end, we examined associations of BMI with putative genetic, neurophysiological, psychiatric, and psychological indicators of impulsivity in 78 women and 74 men formerly dependent on alcohol or drugs. A second analysis was designed to test the replicability of the genetic findings in an independent sample of 109 women and 111 men with a similar history of substance dependence.

RESULTS

The results of the first analysis showed that BMI was positively correlated with Total and Nonplanning Scale Scores on the Barratt Impulsiveness Scale and the number of childhood symptoms of Attention-Deficit/Hyperactivity Disorder in women. It was also positively correlated, in women, with a GABRA2 variant previously implicated as a risk factor for substance dependence and an objective electroencephalographic feature previously associated with GABRA2 and relapse risk. The second analysis confirmed that the correlation between BMI and the substance-dependence-associated GABRA2 genotype was reliable and sex-specific.

CONCLUSIONS

We conclude that an elevated BMI is associated with genetic, neurophysiological, psychiatric, and psychological indicators of impulsivity. The sex difference may be explained by greater opportunities to eat and overeat, a preference for higher calorie foods, a longer duration of alcohol/drug abstinence, or previous pregnancies in women.

Attention deficit hyperactivity symptoms and risky sexual behavior in young adult women

BACKGROUND

This study was undertaken to assess the association between adult attention deficit/hyperactivity disorder (ADHD) symptoms and high-risk sexual behavior.

METHODS

This cross-sectional study interviewed 462 low-income women aged 18-30 years. We used the 18-item Adult ADHD Self-Report Scale (ASRS-v1.1) Symptom Checklist to assess ADHD symptoms. Risky sexual behaviors included sex before 15 years of age, risky sex partners in lifetime, number of sex partners in the last 12 months, condom use in the last 12 months, alcohol use before sex in the last 12 months, traded sex in lifetime, and diagnosed with sexually transmitted infection (STI) in lifetime.

RESULTS

Mean ADHD symptom score was 19.8 (SD±12.9), and summary index of all risky sexual behavior was 1.77 (SD±1.37). Using unadjusted odds ratios (OR), women who endorsed more ADHD symptoms reported engaging in more risky sexual behaviors of all types. However, when multivariable logistic regression was applied adjusting for various sociodemographic covariates, the adjusted ORs remained significant for having risky sex partners and having ≥3 sex partners in the prior 12 months. We observed some differences in risky sexual behavior between two domains of ADHD.

CONCLUSIONS

The ADHD symptom score appears to be associated with some risky sexual behaviors and deserves further attention. A brief ADHD screening can identify this high-risk group for timely evaluation and safe sex counseling.

Interactive effects of HIV/AIDS, body mass, and substance abuse on the frontal brain: a P300 study

In view of the rising prevalence of an overweight body mass among patients living with human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS), clinicians must now be mindful of possible adverse outcomes resulting from the co-occurrence. The present study was designed to examine the additive and interactive effects of HIV/AIDS and an excess body mass, as well as the additional contributions of substance abuse or dependence. The dependent variable was brain function estimated by the measurement of P300 electroencephalographic potentials. P300 potentials were recorded during a task designed to elicit subcomponents with frontal (P300a) and both frontal and non-frontal (P300b) generators. Analyses revealed greater frontal P300a latencies among the 102 HIV-1 seropositive versus the 68 seronegative participants. In addition, frontal P300a latency was further increased by a synergistic interaction of HIV-1 serostatus with a body mass index (BMI)≥25 kg/m². A history of substance abuse/dependence did not alter these changes. However, it did combine with HIV/AIDS to produce a smaller P300a amplitude than was seen in participants with neither disorder. The findings suggest that white matter changes accompanying an excess BMI may exacerbate those that attend HIV/AIDS and thereby slow down frontal brain function. Substance abuse, likewise, interacts with HIV/AIDS but may impair frontal brain function via a different mechanism.

P300 and the stroop effect in overweight minority adolescents

AIM

The goal was to examine the relationship between a risk factor for poor cognitive control and a health outcome of growing public significance--an excess body mass--among adolescents.

METHODS

To this end, 109 adolescents aged 14-20 years were recruited and assigned to 1 of 4 groups defined by the crossing of the absence versus presence of a parental history (PH) of externalizing disorders with a body mass index (BMI) percentile (BMIP) < 85 versus > or = 85. The principal measure estimating cognitive control was the P300 event-related electroencephalographic response recorded during the Stroop task.

RESULTS

The analyses revealed a synergistic interaction between BMIP rank, PH and trial type: the increase in P300 latency and the decrease in response accuracy, elicited by the presence of interfering information, were markedly greater in high-BMIP subjects with a PH of externalizing disorders than in the other subject groups. Analyses of a later component, the N450, previously associated with the Stroop interference effect, revealed no effect of BMI or PH.

CONCLUSIONS

We conclude that subjects with both a PH of externalizing disorders and an excess BMI constitute a unique group that is less able to resolve cognitive conflict than others. The excessive delay in P300 evoked by conflicting response demands in these subjects may be a marker of a heritable factor that increases risk for both excess body mass and substance use disorders.

Priming deficiency in male subjects at risk for alcoholism: the N4 during a lexical decision task

BACKGROUND

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.

METHOD

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.

RESULTS

A significant interaction effect was observed between semantic condition and group, where HR subjects did not show N4 attenuation for primed stimuli.

CONCLUSION

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.

Association of single nucleotide polymorphisms in a glutamate receptor gene (GRM8) with theta power of event-related oscillations and alcohol dependence

Evidence suggests the P3 amplitude of the event-related potential and its underlying superimposed event-related oscillations (EROs), primarily in the theta (4-5 Hz) and delta (1-3 Hz) frequencies, as endophenotypes for the risk of alcoholism and other disinhibitory disorders. Major neurochemical substrates contributing to theta and delta rhythms and P3 involve strong GABAergic, cholinergic and glutamatergic system interactions. The aim of this study was to test the potential associations between single nucleotide polymorphisms (SNPs) in glutamate receptor genes and ERO quantitative traits. GRM8 was selected because it maps at chromosome 7q31.3-q32.1 under the peak region where we previously identified significant linkage (peak LOD = 3.5) using a genome-wide linkage scan of the same phenotype (event-related theta band for the target visual stimuli). Neural activities recorded from scalp electrodes during a visual oddball task in which rare target elicited P3s were analyzed in a subset of the Collaborative Study on the Genetics of Alcoholism (COGA) sample comprising 1,049 Caucasian subjects from 209 families (with 472 DSM-IV alcohol dependent individuals). The family-based association test (FBAT) detected significant association (P < 0.05) with multiple SNPs in the GRM8 gene and event-related theta power to target visual stimuli, and also with alcohol dependence, even after correction for multiple comparisons by false discovery rate (FDR). Our results suggest that variation in GRM8 may be involved in modulating event-related theta oscillations during information processing and also in vulnerability to alcoholism. These findings underscore the utility of electrophysiology and the endophenotype approach in the genetic study of psychiatric disorders.

Recent EEG and ERP findings in substance abusers

Research on electroencephalographic (EEG) correlates of substance use has a long history. The present paper provides a review of recent studies--2001 to the present--with a focus on EEG findings in human participants characterized by a history of chronic substance use, abuse or dependence. In some areas (e.g., alcohol and cocaine dependence), the field has attempted to build upon earlier work by incorporating different methodologies or pursuing research questions of a transdisciplinary nature. New areas of inquiry, such as the investigation of EEG differences among users of ecstasy (MDMA) and methamphetamine, have emerged, primarily as a result of an alarming rise in popularity of these drugs.

Psychiatric and neurophysiological predictors of obesity in HIV/AIDS

The objective of the study was to identify predictors of obesity. One hundred eleven nonobese and 48 obese HIV-1 seropositive patients provided information on medical history and other characteristics. They were then asked to detect the passage of 2-s time intervals while the contingent negative variation (CNV) was recorded. Obese patients were healthier, more likely to be receiving Highly Active Antiretroviral Therapy, and less likely to be substance dependent. Obese patients also exhibited a greater CNV slope and responded prematurely. A path model suggested that CD4+count and protease inhibitor use directly predicted obesity. Depression had no direct effect. However, when incorporated into a hypothetical construct, "mood dysregulation," that also included childhood conduct problems and stimulant dependence, the shared variance among the indicators did predict obesity. This relationship was mediated through premature response preparation (anterior scalp CNV amplitude) and its hypothesized association with impatience/impulsivity.

The effects of HIV on P300 are moderated by familial risk for substance dependence: implications for a theory of brain reserve

BACKGROUND

The goal of the study was to test the validity of additive versus synergistic versus underadditive versions of brain reserve theory within the context of HIV/AIDS. In addition, it tested the convergent validity of 2 operational definitions of premorbid reserve: verbal IQ (VIQ) and a family history (FH) of substance abuse or dependence.

METHODS

Seventy HIV-1 seronegative and 115 HIV-1 seropositive male and female volunteers were assigned to 4 subgroups defined by the crossing of a VIQ score < versus > or = 90 with the presence versus absence of a paternal history of alcohol, cocaine, or opiate abuse or dependence. The principal dependent measure was the P300 event related brain potential elicited during the Stroop color-word interference task.

RESULTS

The principal finding was an underadditive effect of FH plus HIV/AIDS on P300 area over the frontal region: FH reduced frontal scalp P300 to such a degree that the additional effects of HIV/AIDS were blunted. The alternate operational definition of brain reserve, VIQ, had no effect on P300 and did not alter the effects of HIV/AIDS.

CONCLUSIONS

Familial risk for substance dependence and low VIQ compromise different aspects of brain structure and/or function and therefore differ in their relationship to HIV/AIDS and P300. Genetic differences associated with familial risk may reduce brain reserve to such a degree that the neurophysiological effects of HIV/AIDS can no longer be measured.

A family history of psychopathology modifies the decrement in cognitive control among patients with HIV/AIDS

The present study was designed to evaluate the effect of HIV/AIDS on cognitive control and to determine if the effect is modified by familial risk for either alcohol or mood disorders. Sixty HIV-1 seropositive and 75 seronegative volunteers were assigned to four subgroups defined by the crossing of a diagnosis of alcohol dependence in the biological father with diagnoses of either major depressive disorder or bipolar disorder in the biological mother. Cognitive control was evaluated during a task in which subjects were asked, on occasion, to inhibit the impulse to respond in the same physical direction as the stimulus and instead respond in the opposite direction. Event related brain potentials and measures of task performance were recorded. The task evoked a negative shift in a late slow potential (SP) as well as an increment in reaction time when cognitive control was challenged. An important finding was an interaction between trial type, HIV/AIDS, and family history: HIV/AIDS and family history each attenuated the negative shift in the SP to such a degree that no further attenuation could be accomplished by the other. The effects of familial risk for alcohol versus mood disorders were equivalent. In conclusion, the absence of change in a late slow potential following a challenge to cognitive control may represent a marker of familial risk for both externalizing and internalizing disorders. The effects of familial risk on this slow potential are sufficiently robust as to attenuate the effects of HIV/AIDS on the probable generators of the response: the anterior cingulate and prefrontal cortex.

Variation in GABRA2 predicts drinking behavior in project MATCH subjects

BACKGROUND

Previous studies demonstrated, and replicated, an association between single nucleotide polymorphisms (SNPs) within the GABRA2 gene and risk for alcohol dependence. The present study examines the association of a GABRA2 SNP with another definition of alcohol involvement and with the effects of psychosocial treatment.

METHODS

European-American subjects (n = 812, 73.4% male) provided DNA samples for the analysis. All were participants in Project Matching Alcoholism Treatment to Client Heterogeneity (MATCH), a multi-center randomized clinical trial evaluating the efficacy of 3 types of psychosocial treatment for alcoholism: Cognitive Behavioral Therapy (CBT), Motivational Enhancement Therapy (MET), or twelve-step facilitation (TSF). The daily probabilities of drinking and heavy drinking were estimated during the 12-week treatment and 12-month post-treatment periods.

RESULTS

Subjects homozygous for the allele associated with low risk for alcohol dependence in previous studies had lower daily probabilities of drinking and heavy drinking in the present study. This low-risk allele was also associated with a greater difference in drinking outcomes between the treatments. In addition, it enhanced the relative superiority of TSF over CBT and MET. Population stratification was excluded as a confound using ancestry informative marker analysis.

CONCLUSIONS

The assessment of genetic vulnerability may be relevant to studies of the efficacy of psychosocial treatment: GABRA2 genotype modifies the variance in drinking and can therefore moderate power for resolving differences between treatments.

Delta and theta oscillations as risk markers in adolescent offspring of alcoholics

BACKGROUND

Visual P300 is consistently lower in alcohol-dependent individuals, their offspring and subjects at risk. Delta and theta event-related oscillations (ERO) are the major contributors to the P300 signal. The total and evoked power in delta and theta bands in the 300 to 700 ms post-stimulus window (corresponding to the zone of P300 maxima) was compared between adolescent offspring of alcoholics (high-risk) and age-matched normal controls (low-risk), to assess the utility of the risk markers.

METHODS

EEG was recorded during the performance of a visual oddball task. The S-transform algorithm decomposed the EEG signals into different frequency bands and the group differences in total and evoked power in the oscillatory responses during the P300 time window (300 to 700 ms) were analyzed using a multivariate design. Similar analysis was performed on P300 peak amplitude for the target.

RESULTS

The high-risk group showed significantly lower parietal post-stimulus evoked and total power in the delta band for targets. A decrease in total power was seen centrally and parietally in the theta band. The P300 peak amplitude in the parietal electrodes was also significantly lower in the high-risk group.

CONCLUSIONS

The decreased total theta power and total and evoked delta power for visual targets in high risk individuals may serve as an endophenotypic marker in the development of alcoholism and other disinhibitory disorders. The differences seen between the offspring of alcoholics and controls may have a cholinergic basis. The ERO measures appear to be more robust than the P300 amplitude in differentiating the groups.

Delta and theta oscillations as risk markers in adolescent offspring of alcoholics

BACKGROUND

Visual P300 is consistently lower in alcohol-dependent individuals, their offspring and subjects at risk. Delta and theta event-related oscillations (ERO) are the major contributors to the P300 signal. The total and evoked power in delta and theta bands in the 300 to 700 ms post-stimulus window (corresponding to the zone of P300 maxima) was compared between adolescent offspring of alcoholics (high-risk) and age-matched normal controls (low-risk), to assess the utility of the risk markers.

METHODS

EEG was recorded during the performance of a visual oddball task. The S-transform algorithm decomposed the EEG signals into different frequency bands and the group differences in total and evoked power in the oscillatory responses during the P300 time window (300 to 700 ms) were analyzed using a multivariate design. Similar analysis was performed on P300 peak amplitude for the target.

RESULTS

The high-risk group showed significantly lower parietal post-stimulus evoked and total power in the delta band for targets. A decrease in total power was seen centrally and parietally in the theta band. The P300 peak amplitude in the parietal electrodes was also significantly lower in the high-risk group.

CONCLUSIONS

The decreased total theta power and total and evoked delta power for visual targets in high risk individuals may serve as an endophenotypic marker in the development of alcoholism and other disinhibitory disorders. The differences seen between the offspring of alcoholics and controls may have a cholinergic basis. The ERO measures appear to be more robust than the P300 amplitude in differentiating the groups.

Evoked gamma band response in male adolescent subjects at high risk for alcoholism during a visual oddball task

This study investigates early evoked gamma band activity in male adolescent subjects at high risk for alcoholism (HR; n=68) and normal controls (LR; n=27) during a visual oddball task. A time-frequency representation method was applied to EEG data in order to obtain stimulus related early evoked (phase-locked) gamma band activity (29-45 Hz) and was analyzed within a 0-150 ms time window range. Significant reduction of the early evoked gamma band response in the frontal and parietal regions during target stimulus processing was observed in HR subjects compared to LR subjects. Additionally, the HR group showed less differentiation between target and non-target stimuli in both frontal and parietal regions compared to the LR group, indicating difficulty in early stimulus processing, probably due to a dysfunctional frontoparietal attentional network. The results indicate that the deficient early evoked gamma band response may precede the development of alcoholism and could be a potential endophenotypic marker of alcoholism risk.

Patterns of Regional Brain Activity in Alcohol-Dependent Subjects

BACKGROUND

Electroencephalographic (EEG) measures of hemispheric asymmetry in anterior brain activity have been related to a variety of indices of psychopathology and emotionality. However, little is known about patterns of frontal asymmetry in alcohol-dependent (AD) samples. It is also unclear whether psychiatric comorbidity in AD subjects accounts for additional variance in frontal asymmetry, beyond a diagnosis of AD alone.

METHODS

We compared 193 AD subjects with 108 control subjects on resting brain activity in anterior and posterior regions, as indexed by asymmetries in alpha band power in the left and right hemispheres. Within the AD group alone, we examined whether comorbid major depressive disorder (MDD) or antisocial personality disorder (ASPD) had effects on regional asymmetry.

RESULTS

Compared with control subjects, AD subjects exhibited lower left, relative to right, cortical activation in anterior regions. Evidence that comorbidity in AD subjects accounted for further variance in EEG asymmetry was mixed; AD subjects with comorbid ASPD were not significantly different from those without ASPD, while AD subjects with a lifetime history of MDD showed less asymmetry in anterior regions than those without MDD.

CONCLUSIONS

Our findings indicate that AD subjects exhibit a pattern of frontal asymmetry similar to that found in other psychiatric groups. Results examining the effects of comorbidity in AD on EEG asymmetry were inconclusive. The implications of our findings for future work are described.

A Cholinergic Receptor Gene (CHRM2) Affects Event-related Oscillations

We report genetic linkage and association findings which implicate the gene encoding the muscarinic acetylcholine receptor M2 (CHRM2) in the modulation of a scalp-recorded electrophysiological phenotype. The P3 (P300) response was evoked using a three-stimulus visual oddball paradigm and a phenotype that relates to the energy in the theta band (4-5 Hz) was analyzed. Studies have shown that similar electrophysiological measures represent cognitive correlates of attention, working memory, and response selection; a role has been suggested for the ascending cholinergic pathway in the same functions. The results of our genetic association tests, combined with knowledge regarding the presence of presynaptic cholinergic M2 autoreceptors in the basal forebrain, indicate that the cognitive processes required by the experiment may in part be mediated by inhibitory neural networks. These findings underscore the utility of electrophysiology and neurogenetics in the understanding of cognitive function and the study of brain-related disorders.

Interactive effects of hypertension and alcohol dependence on the P300 event-related potential in African-Americans

Although hypertension and alcohol dependence have been linked by epidemiological surveys and clinical observations, their interactive effects on brain function have rarely been tested. The present study involved the recording of P300 event related potentials (ERP) from 106 middle-aged African-American adults assigned to one of four groups: normotensive/nondependent (n=56), hypertensive/nondependent (n=11), normotensive/dependent (n=27), and hypertensive/dependent (n=12). The numbers of Nicotine Dependence, Major Depressive Disorder, and Conduct Disorder symptoms were specified as covariates within a 2 by 2 factorial design. ERPs were recorded during separate visual and auditory oddball tasks. The major result was a synergistic effect of hypertension and alcohol dependence on auditory P300 latency: the combination of both factors was associated with greater slowing than the sum of their independent effects. Future studies should continue to examine the potential synergistic effects of alcohol dependence and hypertension with a view toward identifying and reducing neurophysiological decrements and stroke risk among middle-aged patients.

Brain maturation in conduct disorder versus borderline personality disorder

Conduct disorder (CD) and borderline personality disorder (BPD) have been associated with abnormalities in brain function. The present study assessed whether adolescents with significant symptoms of CD and BPD display abnormal brain maturation. Participants recruited from the community were categorized as CD only, BPD only, CD plus BPD, or controls with neither CD nor BPD. Brain maturation was estimated by the amplitude difference in the P300 event-related brain potential between participants < versus > or = 17 years old. With increasing age, controls and BPD only participants exhibited a P300 amplitude decline. This pattern was not evident in the CD only and CD plus BPD groups. The different brain maturation patterns seen in adolescents with CD versus BPD symptoms may contribute to differences in age-of-onset, clinical course, and resistance to treatment.

ASPD blunts the effects of HIV and antiretroviral treatment on event-related brain potentials

Several studies have demonstrated that antiretroviral therapy diminishes the adverse effects of HIV/AIDS on brain function. Yet, few studies have examined the role of comorbid psychiatric disorders in limiting the magnitude of recovery. The present study examined the effects of the presence versus absence of one such disorder--antisocial personality disorder (ASPD)--on brain function in an HIV-1 seronegative control group (n=68) and in HIV-1 seropositive patients receiving (n=26), versus not receiving (n=71), antiretroviral treatment. The primary dependent measures of brain function were the amplitude, latency, and topography of the P300 event-related potential. ANCOVA revealed a significant main effect of ASPD as well as an interaction between ASPD and HIV-1/treatment status. Participants with ASPD exhibited a significant decrement in frontal P300 amplitude in comparison to the ASPD-negative groups. More importantly, further analyses showed that ASPD blunted the decrement in P300 accompanying untreated HIV/AIDS as well as the improvement in P300 accompanying antiretroviral treatment. The results suggest that P300 is minimally improved by antiretroviral therapy among HIV-1 seropositive patients with comorbid ASPD. The lack of antiretroviral efficacy is not easily explained by poor medication compliance. The diminished response to treatment is more likely related to a pre-existing neurophysiological decrement localized to the same brain regions where HIV/AIDS and antiretroviral treatment exert their maximal effect.

N400 as an index of semantic expectancies: differential effects of alcohol and cocaine dependence

BACKGROUND

Chronic substance abuse has been associated with decrements in the processing and expression of language. The present study utilized the N400 event-related electroencephalographic potential to index semantic processing in 133 adults with (n=49) or without (n=84) a history of alcohol and/or cocaine dependence. The contributions of age, gender, and comorbid marijuana and nicotine dependence, and antisocial symptomology to N400 decrements were either covaried or controlled.

METHODS

A continuous series of 300 stimuli was presented for 150 ms each (interstimulus interval=1475 ms) on a computer screen. The series was arranged such that a word (approximately 17% of stimuli) immediately preceded presentations of its antonym (primed condition; approximately 17% of stimuli), or a semantically unrelated word (unprimed condition; approximately 17% of stimuli). The remaining 50% of stimuli consisted of unpronounceable letter combinations (non-word condition). EEG responses to the antonyms, unrelated words, and letter jumbles were retained for analysis. Throughout the task, the subject pressed response keys to discriminate words from non-words.

RESULTS

Analyses revealed a detrimental effect of alcohol dependence on N400 amplitude and no significant main or interactive effects of cocaine dependence.

CONCLUSION

The present findings suggest that alcohol-dependent individuals may exhibit verbal processing decrements. These findings also challenge hypotheses suggesting that the combined use of cocaine and alcohol is more deleterious to brain function than alcohol use alone.

Borderline personality disorder features in adolescent girls: P300 evidence of altered brain maturation

OBJECTIVE

To examine brain maturation in adolescent girls with borderline personality disorder (BPD) features using the P300 event-related potential.

METHODS

One hundred twenty-three girls, aged 14-19 yrs, were assigned to one of 4 groups formed by the crossing of BPD features (vs. > or =5 BPD criteria) and median age (vs. >16.5 yrs). P300 responses were measured while subjects performed a complex visual oddball task.

RESULTS

ANCOVAs of P300 amplitude-adjusting for variability associated with comorbid conduct disorder and depression symptoms--revealed a significant interaction. Among subjects without BPD features, aging was associated with the normal reduction in visual P300 amplitude. Among subjects with BPD features, there were no age-related changes. Additional analyses, which tested the effects of BPD features across the full age range, supported these findings.

CONCLUSIONS

The present findings suggest abnormal brain maturation among adolescent girls exhibiting features of BPD.

SIGNIFICANCE

These results support a hypothesis of altered brain maturation in adolescents exhibiting BPD features at an early age. It is suggested that measures of brain maturation obtained during adolescence may improve our ability to predict BPD and comorbid disorders in adulthood.

Sensorimotor dysfunction in HIV/AIDS: effects of antiretroviral treatment and comorbid psychiatric disorders

OBJECTIVES

Balance and gait problems have repeatedly been mentioned in case descriptions of patients infected with Human Immunodeficiency Virus (HIV-1). Objective evidence of these problems has rarely been reported, however. Furthermore, the extent to which balance and gait are influenced by antiretroviral medications or comorbid psychiatric disorders has rarely been examined.

DESIGN

The study compared 78 HIV-1 seronegative volunteers to 28 HIV/AIDS patients receiving no antiretroviral therapy, 25 patients receiving only nucleoside analogue therapy, and 37 patients receiving Highly Active Antiretroviral Therapy (HAART).

METHODS

The dependent measures included Equilibrium Quotient scores recorded during 3 subtests of the Sensory Organization Test (SOT), the number of falls during each subtest, the functional base of support, gait speed and cadence, single leg balance time, proximal strength, and vibrotactile threshold of the foot. The analysis employed the number of alcohol and drug abuse problems, depression severity, and body mass index as covariates.

RESULTS

ANCOVAs revealed significant decrements in the 3 HIV-1 seropositive groups relative to the control group on Equilibrium Quotient scores during the most difficult of the SOT subtests (sway-referenced support surface with eyes-closed). HIV/AIDS patients also exhibited a smaller functional base of support and greater vibrotactile thresholds. Antiretroviral treatment did not affect balance; but, it did alter sensory threshold in a complex manner.

CONCLUSIONS

HIV/AIDS is associated with reliable decrements in balance and peripheral sensory function which are variably sensitive to antiretroviral treatment. The implications of these findings for mobility, and workplace or operator safety, should be contemplated.

Linkage and linkage disequilibrium of evoked EEG oscillations with CHRM2 receptor gene polymorphisms: implications for human brain dynamics and cognition

Event-related oscillations (ERO) offer an alternative theoretical and methodological approach to the analysis of event-related EEG responses. The P300 event-related potential (ERP) is elicited through the superposition of the delta (1-3 Hz) and theta (3-7 Hz) band oscillatory responses. The cholinergic neurotransmitter system has a key function in modulating excitatory post-synaptic potentials caused by glutamate, and therefore influences P300 generation and the underlying oscillatory responses. Here we report significant linkage and linkage disequilibrium between target case frontal theta band, visual evoked brain oscillations and a single nucleotide polymorphism (SNP) from the cholinergic muscarinic receptor gene (CHRM2) on chromosome 7. We also demonstrate significant linkage disequilibrium between CHRM2 SNPs and target case parietal delta band visual evoked oscillations (LD P<0.001). These findings were not observed for the equivalent non-target case data, suggesting a role for the CHRM2 gene in higher cognitive processing in humans.

Effects of borderline personality disorder features and a family history of alcohol or drug dependence on P300 in adolescents

Decrements in P300 amplitude have been associated with familial risk for alcoholism as well as several other psychiatric disorders characterized by disinhibited behavior. The present study examined the P300 in relation to Borderline Personality Disorder (BPD) features in adolescents with a paternal history of alcohol or drug dependence. One hundred and seventy-five males and females, aged 14-20, were assigned to groups based on BPD features (BPD+ vs. BPD-), family history of substance dependence (negative FH-, alcohol FHA, drug FHD) and gender. BPD features were assessed using the Structured Clinical Interview for the DSM-III-R questionnaire. P300 ERPs were recorded while each subject performed the Stroop color-word compatibility test. Repeated measures analyses, which included Conduct Disorder and Depression symptoms as covariates, indicated a significant reduction in P300 amplitude in the BPD+ group. There were no significant effects of FH or gender on P300 amplitude. These results document the presence of neurophysiological abnormalities associated with BPD features in an adolescent sample. This effect appeared to be independent of a family history of alcohol or substance dependence. These findings suggest that BPD symptoms during adolescence are relevant to the examination of the physiological antecedents of those forms of adult psychopathology characterized by behavioral disinhibition, including alcohol and drug dependence.

P300 evidence of cognitive inflexibility in female adolescents at risk for recurrent depression

Studies utilizing the P300 event-related potential (ERP) to document potential neurophysiological deficits related to depression have produced variable findings. The present investigation examined the effects of two tasks to determine whether one task would be more sensitive to a history of depression. We examined 124 female subjects, aged 14-20 years. Each subject was assigned to either a history of depression (DEP-Hx) or control group based on the presence versus absence of a DSM-III-R Major Depressive Episode. ERPs were recorded during two auditory oddball tasks. The first task was a simple two-pitch auditory discrimination and the second task was a three-stimulus auditory discrimination. In both tasks, subjects responded to the same rare target tone. Analysis of P300 amplitudes indicated a significant group by task interaction. Simple effects indicated that control subjects exhibited smaller target P300 amplitudes during the three-stimulus task as compared to the two-stimulus task. In contrast, subjects with a history of depression did not show a significant difference in P300 target amplitude between the two tasks. These results suggest that depression history as well as task difficulty/modality may influence the utility of the P300 in documenting the neurophysiological aspects of depression.

Variations in GABRA2, encoding the alpha 2 subunit of the GABA(A) receptor, are associated with alcohol dependence and with brain oscillations

Alcoholism is a complex disease with both genetic and environmental risk factors. To identify genes that affect the risk for alcoholism, we systematically ascertained and carefully assessed individuals in families with multiple alcoholics. Linkage and association analyses suggested that a region of chromosome 4p contained genes affecting a quantitative endophenotype, brain oscillations in the beta frequency range (13-28 Hz), and the risk for alcoholism. To identify the individual genes that affect these phenotypes, we performed linkage disequilibrium analyses of 69 single-nucleotide polymorphism (SNPs) within a cluster of four GABA(A) receptor genes, GABRG1, GABRA2, GABRA4, and GABRB1, at the center of the linked region. GABA(A) receptors mediate important effects of alcohol and also modulate beta frequencies. Thirty-one SNPs in GABRA2, but only 1 of the 20 SNPs in the flanking genes, showed significant association with alcoholism. Twenty-five of the GABRA2 SNPs, but only one of the SNPs in the flanking genes, were associated with the brain oscillations in the beta frequency. The region of strongest association with alcohol dependence extended from intron 3 past the 3' end of GABRA2; all 43 of the consecutive three-SNP haplotypes in this region of GABRA2 were highly significant. A three-SNP haplotype was associated with alcoholism, with P=.000000022. No coding differences were found between the high-risk and low-risk haplotypes, suggesting that the effect is mediated through gene regulation. The very strong association of GABRA2 with both alcohol dependence and the beta frequency of the electroencephalogram, combined with biological evidence for a role of this gene in both phenotypes, suggest that GABRA2 might influence susceptibility to alcohol dependence by modulating the level of neural excitation.

Resting EEG in offspring of male alcoholics: beta frequencies

This study examines the differences in beta (12-28 Hz) band power in offspring of male alcoholics from densely affected alcoholic families. We have attempted to investigate if the increase in beta power is a 'state' or 'trait' marker for alcoholism. This study also explores the gender differences in the expression of this potential risk marker. Absolute beta power in three bands-beta 1(12-16 Hz), beta 2 (16-20 Hz), and beta 3 (20-28 Hz)-in the eyes closed EEG of 171 high risk (HR) subjects who were offspring of male alcoholics and 204 low risk (LR) subjects with no family history of alcoholism, were compared for each gender separately using a repeated measures analysis of variance design. Alcoholic and non-alcoholic subjects within the high risk group were compared using a repeated measures design as a follow-up analysis. The present study demonstrated increased beta power in the resting EEG of offspring of male alcoholics. Male HR subjects had higher beta 1 (12-16 Hz) power and female HR subjects had increased power in beta 2 (16-20 Hz) and beta 3 (20-28 Hz) as compared with low risk participants. Female HR subjects also showed significantly increased beta 2 and beta 3 power if they had two or more alcoholic first-degree relatives when compared with HR females having only an affected father. Risk characteristics are expressed differentially in males and females and may be an index of differential vulnerability to alcoholism. The results indicate that increased EEG beta power can be considered as a likely marker of risk for developing alcoholism and may be used as a predictive endophenotype.

Depression and familial risk for substance dependence: a P300 study of young women

The present study evaluated the effects of depression and a family history of alcohol or substance dependence on P300 event-related potentials in young women aged 14 to 20 years. Of the 130 female subjects, 29 met DSM-III-R diagnostic criteria for a lifetime history of a Major Depressive Episode. Event-related electroencephalographic potentials were recorded from each subject while she performed a complex visual oddball task. Analyses indicated a decrement in P300 amplitude in the depressed group as compared to girls with no history of depression. No effects of family history of alcoholism or drug dependence were detected. Current source density analyses, utilizing a realistic head-shape boundary element model, indicated that the difference between the depressed and non-depressed groups was maximal in the right prefrontal region. These results provide further support for the notion that the cognitive difficulties associated with depression are subtle and best detected with sensitive neurophysiological indices, such as P300.

Brain maturation and subtypes of conduct disorder: interactive effects on p300 amplitude and topography in male adolescents

OBJECTIVE

Adolescents with conduct disorder problems are, on average, at increased risk for a variety of unfortunate adult outcomes, including substance dependence. This study was designed to identify the neurophysiological correlates of different categories of conduct disorder problems as well as the relationship between these correlates and the maturational status of the brain.

METHOD

The subjects were 94 males, aged 14-19 years, recruited from the community. None were recruited from treatment or juvenile justice programs. The subjects varied in the type and number of conduct problem behaviors exhibited prior to age 15. Groups were operationally defined by the relative number (0 versus > or =1) of DSM-IV conduct disorder diagnostic criteria within each of four categories: rules violations, aggression, deceitfulness/theft, and destructiveness. Age was included as an additional grouping factor. P300 electroencephalographic potentials were recorded while subjects performed a task in which rare auditory stimuli were used to signal a change in stimulus-response mapping during a succeeding set of trials.

RESULTS

Analyses revealed that boys with a history of rules violations failed to exhibit the normal maturational increase in P300 amplitude found in boys without a history of rules violations. Topographic analyses of current source densities suggest that the source of the maturational deficit involved P300 generators within the frontal brain. Parietal generators of P300 matured normally.

CONCLUSIONS

The present results are interpreted as reflecting a decrement in frontal brain maturation among boys potentially at risk for substance dependence, antisocial personality disorder, or other forms of adult psychopathology.

Lateral asymmetries in the frontal brain: effects of depression and a family history of alcoholism in female adolescents

BACKGROUND

Subtle electroencephalographic (EEG) abnormalities have been detected among subjects with depressed affect. The present study attempted to discern whether these abnormalities reflect a main effect or an interaction between depression and either of two family history variables--a family history of alcoholism or a family history of depression.

METHODS

The subjects were 151 adolescent females, aged 14 to 20 years, of whom 58 met DSM-III-R diagnostic criteria for a lifetime history of a major depressive episode. The electroencephalogram was recorded from 31 electrode sites while the subjects sat relaxed, with their eyes open, for 5 min.

RESULTS

Analyses of EEG data revealed that a personal history of depression and a family history of alcoholism had opposite effects on the EEG power spectrum. Depression was associated with an increase in alpha power (7.5-12.5 Hz). In contrast, a family history of alcoholism was associated with an increase in fast beta power (19-30 Hz) and a decrease in theta power (4-7 Hz). There were no significant main or interactive effects of a family history of depression. Current source density topographic analyses of the significant group differences in alpha and fast beta power demonstrated that the effects of depression could be localized to the right frontal brain, whereas the effects of a family history of alcoholism were localized to the left frontal area.

CONCLUSIONS

The laterally opposite effects of depression and a family history of alcoholism suggest a high level of functional differentiation of the frontal brain. They also suggest that the different neurophysiological substrates of depression and familial risk can be distinguished through the use of modern methods of EEG source localization.

Beta power in the EEG of alcoholics

BACKGROUND

In this study, the magnitude and spatial distribution of beta power in the resting electroencephalogram (EEG) were examined to address the possibility of an excitation-inhibition imbalance in the central nervous system of alcoholics.

METHODS

Log transformed absolute power in the Beta 1 (12.5-16 Hz), Beta 2 (16.5-20 Hz), and Beta 3 (20.5-28 Hz) bands in the eyes-closed EEG of 307 alcohol-dependent subjects and 307 unaffected age- and gender-matched control subjects were compared using a multivariate repeated measures design. Effect of gender, age, and drinking variables was examined separately.

RESULTS

Increased Beta 1 (12.5-16 Hz) and Beta 2 (16.5-20 Hz) absolute power was observed in alcohol-dependent subjects at all loci over the scalp. The increase was most prominent in the central region. Increased Beta 3 (20.5-28 Hz) power was frontal in the alcoholics. Age and clinical variables did not influence the increase. Male alcoholics had significantly higher beta power in all three bands. In female alcoholics the increase did not reach statistical significance.

CONCLUSIONS

Beta power in all three bands of resting EEG is elevated in alcoholics. This feature is more prominent in male alcoholics. The increased beta power in the resting EEG may be an electrophysiological index of the imbalance in the excitation-inhibition homeostasis in the cortex.

Linkage and linkage disequilibrium mapping of ERP and EEG phenotypes

Linkage analyses of highly heritable electrophysiological phenotypes (EEG, ERP) that can potentially identify individuals at risk for alcoholism were performed on a large sample of families with a high density of alcohol dependence as part of the Collaborative Study on the Genetics of Alcoholism (COGA); these genetic findings are summarized. Quantitative trait loci (QTLs) were identified for several ERP characteristics (P300, N100, N400) and for the beta frequencies of the EEG where we report linkage and linkage disequilibrium at a GABA(A) receptor gene on chromosome 4. Genetic analyses of ERPs suggest that several regions of the human genome contain genetic loci related to the generation of N100, N400 and P300, which are possible candidate loci underlying the functional organization of human neuroelectric activity. The advent of genomics and proteomics and a fuller understanding of gene regulation, will open new horizons on the critical electrical events so essential for human brain function.

Differential effects of alcohol, cocaine, and opioid abuse on event-related potentials recorded during a response competition task

The present study examined the abilities of cocaine-dependent and opioid-dependent patients and healthy, non-dependent volunteers to execute a task requiring rapid shifts in cognitive set. Sixty-six residential treatment program patients, characterized by a history of either cocaine (n=37) or opioid (n=29) dependence, and 18 non-drug-dependent community volunteers were evaluated. The task involved the execution of right- or left-hand button press responses that were either spatially-compatible or incompatible with a directional cue. Performance and event-related electroencephalographic (EEG) activity were recorded throughout the task. Analyses revealed that button press responses were significantly slower and less accurate for all of the groups when spatial conflict was introduced. The amplitude of a slow EEG potential (SP), emerging approximately 500 ms after stimulus onset, showed the normal effect of spatial conflict for the opioid-dependent and non-dependent groups, but not for subjects in the cocaine-dependent group. Correlational analyses restricted to data from the cocaine-dependent group showed that this abnormal SP amplitude was not related to the quantity, frequency, or recency of their cocaine use; it only correlated with their comorbid alcohol use. The results of the major analyses, in combination with the results of a neuroanatomical localization algorithm applied to the SP data, suggest that comorbid alcohol use disrupts normal task-related activation of the anterior cingulate, cerebellum, and prefrontal cortex. The present results have implications for the assessment of specific cognitive problems which could foster drug abuse.