Neurodevelopmental patterns of visual P3b in association with familial risk for alcohol dependence and childhood diagnosis

Epigenetic Effects in HPA Axis Genes Associated with Cortical Thickness, ERP Components and SUD Outcome

Association between familial loading for alcohol use disorders (AUD) and event-related potentials (ERPs) suggests a genetic basis for these oscillations though much less is known about epigenetic pathways influenced by environmental variation. Early life adversity (ELA) influences negative outcomes much later in life. The stress-activated neuropeptide corticotropin-releasing hormone (CRH) contributes to the deleterious effects of ELA on brain structure and function in animals. Accordingly, we hypothesized that ELA would be related to cortical thickness and electrophysiological characteristics through an epigenetic effect on CRH receptor type-1 (CRHR1) methylation. A total of 217 adolescent and young adult participants from either multiplex alcohol dependence or control families were scanned using magnetic resonance imaging (MRI) at 3T and cortical thickness was determined. Longitudinal follow-up across childhood, adolescence, and young adulthood provided developmental ERP data and measures of adversity. Blood samples for genetic and epigenetic analyses were obtained in childhood. Cortical thickness and visual ERP components were analyzed for their association and tested for familial risk group differences. Visual P300 amplitude at Pz and cortical thickness of the left lateral orbitofrontal region (LOFC), were significantly related to risk group status. LOFC cortical thickness showed a negative correlation with CRHR1 methylation status and with childhood total stress scores from the Life Stressors and Social Resources Inventory (LISRES). Stress scores were also significantly related to P300 amplitude recorded in childhood. The present results suggest that early life adversity reflected in greater total LISRES stress scores in childhood can impact the methylation of the CRHR1 gene with implications for brain development as seen in cortical thickness and electrophysiological signals emanating from particular brain regions.

Neural anomalies during vigilance in schizophrenia: Diagnostic specificity and genetic associations

Impaired vigilance is a core cognitive deficit in schizophrenia and may serve as an endophenotype (i.e., mark genetic liability). We used a continuous performance task with perceptually degraded stimuli in schizophrenia patients (N = 48), bipolar disorder patients (N = 26), first-degree biological relatives of schizophrenia patients (N = 55) and bipolar disorder patients (N = 28), as well as healthy controls (N = 68) to clarify whether previously reported vigilance deficits and abnormal neural functions were indicative of genetic liability for schizophrenia as opposed to a generalized liability for severe psychopathology. We also examined variation in the Catechol-O-methyltransferase gene to evaluate whether brain responses were related to genetic variation associated with higher-order cognition. Relatives of schizophrenia patients had an increased rate of misidentification of nontarget stimuli as targets when they were perceptually similar, suggestive of difficulties with contour perception. Larger early visual responses (i.e., N1) were associated with better task performance in patients with schizophrenia consistent with enhanced N1 responses reflecting beneficial neural compensation. Additionally, reduced N2 augmentation to target stimuli was specific to schizophrenia. Both patients with schizophrenia and first-degree relatives displayed reduced late cognitive responses (P3b) that predicted worse performance. First-degree relatives of bipolar patients exhibited performance deficits, and displayed aberrant neural responses that were milder than individuals with liability for schizophrenia and dependent on sex. Variation in the Catechol-O-methyltransferase gene was differentially associated with P3b in schizophrenia and bipolar groups. Poor vigilance in schizophrenia is specifically predicted by a failure to enhance early visual responses, weak augmentation of mid-latency brain responses to targets, and limited engagement of late cognitive responses that may be tied to genetic variation associated with prefrontal dopaminergic availability. Experimental results illustrate specific neural functions that distinguish schizophrenia from bipolar disorder and provides evidence for a putative endophenotype that differentiates genetic liability for schizophrenia from severe mental illness more broadly.

Cognitive Control Deficits in Alcohol Dependence Are a Trait- and State-Dependent Biomarker: An ERP Study

Alcohol dependence (AD) presents cognitive control deficits. Event-related potential (ERP) P300 reflects cognitive control-related processing. The aim of this study was to investigate whether cognitive control deficits are a trait biomarker or a state biomarker in AD. Participants included 30 AD patients and 30 healthy controls (HCs). All participants were measured with P300 evoked by a three-stimulus auditory oddball paradigm at a normal state (time 1, i.e., just after the last alcohol intake) and abstinence (time 2, i.e., just after a 4-week abstinence). The results showed that for P3a and P3b amplitude, the interaction effect for group × time point was significant, the simple effect for group at time 1 level and time 2 level was significant, and the simple effect for time point at AD group level was significant; however, the simple effect for time point at HC group level was not significant. Above results indicated that compared to HCs, AD patients present reductions of P3a/3b amplitude, and after 4-week alcohol abstinence, although P3a/3b amplitudes were improved, they were still lower than those of HCs. For P3a and P3b latencies, no significant differences were observed. These findings conclude that AD patients present cognitive control deficits that are reflected by P3a/3b and that cognitive control deficits in AD are trait- and state-dependent. The implication of these findings is helpful to understand the psychological and neural processes for AD, and these findings suggest that improving the cognitive control function may impact the treatment effect for AD.

P300 development from infancy to adolescence

This article provides an overview of P300 research from infancy through adolescence. First, a brief historical overview is provided highlighting seminal studies that began exploration of the P300 component in developmental groups. Overall, these studies suggest that the P300 can be detected in children and appears to reflect similar cognitive processes to those in adults; however, it is significantly delayed in its latency to peak. Second, two striking findings from developmental research are the lack of a clear P300 component in infancy and differential electrophysiological responses to novel, unexpected stimuli in children, adolescents, and adults. Third, contemporary questions are described, which include P300-like components in infancy, alteration of P300 in atypically developing groups, relations between P300 and behavior, individual differences of P300, and neural substrates of P300 across development. Finally, we conclude with comments regarding the power of a developmental perspective and suggestions for important issues that should be addressed in the next 50 years of P300 research.

Adolescent Alcohol Exposure Persistently Impacts Adult Neurobiology and Behavior

Adolescence is a developmental period when physical and cognitive abilities are optimized, when social skills are consolidated, and when sexuality, adolescent behaviors, and frontal cortical functions mature to adult levels. Adolescents also have unique responses to alcohol compared with adults, being less sensitive to ethanol sedative-motor responses that most likely contribute to binge drinking and blackouts. Population studies find that an early age of drinking onset correlates with increased lifetime risks for the development of alcohol dependence, violence, and injuries. Brain synapses, myelination, and neural circuits mature in adolescence to adult levels in parallel with increased reflection on the consequence of actions and reduced impulsivity and thrill seeking. Alcohol binge drinking could alter human development, but variations in genetics, peer groups, family structure, early life experiences, and the emergence of psychopathology in humans confound studies. As adolescence is common to mammalian species, preclinical models of binge drinking provide insight into the direct impact of alcohol on adolescent development. This review relates human findings to basic science studies, particularly the preclinical studies of the Neurobiology of Adolescent Drinking in Adulthood (NADIA) Consortium. These studies focus on persistent adult changes in neurobiology and behavior following adolescent intermittent ethanol (AIE), a model of underage drinking. NADIA studies and others find that AIE results in the following: increases in adult alcohol drinking, disinhibition, and social anxiety; altered adult synapses, cognition, and sleep; reduced adult neurogenesis, cholinergic, and serotonergic neurons; and increased neuroimmune gene expression and epigenetic modifiers of gene expression. Many of these effects are specific to adolescents and not found in parallel adult studies. AIE can cause a persistence of adolescent-like synaptic physiology, behavior, and sensitivity to alcohol into adulthood. Together, these findings support the hypothesis that adolescent binge drinking leads to long-lasting changes in the adult brain that increase risks of adult psychopathology, particularly for alcohol dependence.

Longitudinal predictors of cannabis use and dependence in offspring from families at ultra high risk for alcohol dependence and in control families

Cannabis use is common among adolescents. Identification of the factors associated with continued heavy use into young adulthood and development of cannabis abuse and dependence is of considerable importance. The role of familial risk for addiction and an associated endophenotype, P300 amplitude, has not previously been related to cannabis use and dependence. A prospective longitudinal study spanning childhood and young adulthood provided the opportunity for exploring these factors, along with genetic variation, in the cannabis use behaviors of 338 young adult offspring from high and low familial risk for alcohol dependence families (ages 19-30). P300 data were collected multiple times in childhood. The association between young adult patterns of cannabis use or cannabis abuse/dependence was tested with genetic variation in the cannabinoid gene, CNR1, the ANKK1-DRD2 gene, and childhood developmental trajectories of P300. Young adult patterns of cannabis use was characterized by three patterns: (i) no use throughout; (ii) declining use from adolescence through young adulthood; and (iii) frequent use throughout. Following the low P300 trajectory in childhood predicted cannabis abuse and dependence by young adulthood. A four SNP ANKK1-DRD2 haplotype (G-G-G-C) was found to be significantly associated with the frequency of use patterns (P = 0.0008). Although CNR1 variation overall was not significantly associated with these patterns, among individuals with cannabis abuse/dependence the presence of one or both copies of the rs806368 A > G minor allele conferred a 5.4-fold increase (P = 0.003) in the likelihood that they would be in the frequent and persistent use group rather than the declining use group.

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.

Psychological and Neurobiological Precursors of Alcohol Use Disorders in High Risk Youth

It has long been known that Alcohol Use Disorders (AUDs) run in families with substantial heritability. Determining the specific genetic underpinnings of these disorders has been challenging because of the clinical heterogeneity and variable expression across the lifespan. The search for endophenotypic biological variation associated with the AUD and related substance use disorder (SUD) phenotypes is based on the belief that an endophenotype is more proximal to the causative gene. Identification of genes conferring increased susceptibility has important implications for treatment through the potential development of medications that target specific genetic pathways. High risk family designs that contrast offspring with and without a familial/genetic background have provided valuable insights into the psychological characteristics (executive control, affective regulation, decision making and social cognition) that differentiate such individuals. The current chapter will review these with a focus on brain morphology of specific regions, the coordinated activity of neural networks, and developmental trajectories of electrophysiological activity.

Genetic psychophysiology: advances, problems, and future directions

This paper presents an overview of historical advances and the current state of genetic psychophysiology, a rapidly developing interdisciplinary research linking genetics, brain, and human behavior, discusses methodological problems, and outlines future directions of research. The main goals of genetic psychophysiology are to elucidate the neural pathways and mechanisms mediating genetic influences on cognition and emotion, identify intermediate brain-based phenotypes for psychopathology, and provide a functional characterization of genes being discovered by large association studies of behavioral phenotypes. Since the initiation of this neurogenetic approach to human individual differences in the 1970s, numerous twin and family studies have provided strong evidence for heritability of diverse aspects of brain function including resting-state brain oscillations, functional connectivity, and event-related neural activity in a variety of cognitive and emotion processing tasks, as well as peripheral psychophysiological responses. These data indicate large differences in the presence and strength of genetic influences across measures and domains, permitting the selection of heritable characteristics for gene finding studies. More recently, candidate gene association studies began to implicate specific genetic variants in different aspects of neurocognition. However, great caution is needed in pursuing this line of research due to its demonstrated proneness to generate false-positive findings. Recent developments in methods for physiological signal analysis, hemodynamic imaging, and genomic technologies offer new exciting opportunities for the investigation of the interplay between genetic and environmental factors in the development of individual differences in behavior, both normal and abnormal.

Cholinergic receptor gene (CHRM2) variation and familial loading for alcohol dependence predict childhood developmental trajectories of P300

P300 amplitude in childhood predicts substance use disorders by young adulthood. Trajectories of visual P300 amplitude show an association between low amplitude P300 and familial risk for alcohol dependence (AD). Variation in the cholinergic muscarinic receptor gene (CHRM2) has previously been associated with P300 amplitude and AD. The present study used group based trajectory modeling of auditory P300 data collected longitudinally from offspring in families with and without familial loading for AD to determine if specific trajectories would be associated with familial risk and CHRM2 variation. Trajectory modeling confirms previous reports of an association between the low visual P300 trajectory with high familial risk in male offspring. This association was detected in offspring in the 8-12 age range, but not in 13-18 or 19-29 year olds or in high-risk female offspring. CHRM2 association analysis with P300 finds 8-12 year olds who are homozygous for the T allele of rs1824024 are 2.6 times more likely to follow a P300 trajectory characterized by lower and slower change regardless of familial loading. Combining the odds for being male and having a TT genotype results in odds of 6.5 that individuals will follow the low P300 trajectory.

White matter microstructure, alcohol exposure, and familial risk for alcohol dependence

Offspring from families with alcohol dependence (AD) have been shown to exhibit brain morphological alterations that appear to be related to their familial/genetic risk for AD. Greater susceptibility for developing AD may be related to structural underpinnings of behavioral traits that predispose to AD. We examined white matter (WM) integrity in 81 individuals with either a high density of AD in their families (N=44) or without a family history for either alcohol or drug dependence (N=37). Magnetic resonance images were acquired on a Siemens 3 T scanner with fractional anistropy (FA) and the apparent diffusion coefficient (ADC), along with radial diffusivity (RD) and longitudinal (axial) diffusivity calculated for major white matter tracts in both hemispheres. Extensive personal histories of alcohol and drug use were available from longitudinal collection of data allowing for reliable estimates of alcohol and drug exposure. We found that the interaction of personal exposure to alcohol and familial risk for AD predicts reduction in WM integrity for the inferior longitudinal fasciculus (ILF) and the superior longitudinal fasciculus (SLF) in the left hemisphere and the forceps major tract. Only one tract showed a significant difference for exposure alone, the anterior thalamic radiation.

Absence of P300 reduction in South African treatment-naïve adolescents with alcohol dependence

BACKGROUND

Event-related potential studies show reduced P300 amplitudes in alcohol use disorders (AUDs). Alcohol exposure, genetic vulnerability to alcoholism, and comorbid psychopathology may contribute to this reduction. Most previous research has studied treated adult AUD samples, which have more severe alcoholism, a greater family history of AUDs, and more comorbidity than untreated samples. Untreated AUD samples tend to have little or no P300 amplitude reduction. We compared P300 between treatment-naïve alcohol-dependent (TNAD) adolescents with no diagnosable substance abuse or psychiatric comorbidity and nonsubstance-abusing control (NSAC) adolescents.

METHODS

Individuals between the ages of 13 and 18 years were recruited into either TNAD (n = 45) or NSAC (n = 64) groups. Alcohol use variables, family history density of alcohol problems, and psychiatric symptom counts were assessed in a clinician-administered evaluation. EEGs were recorded during performance of a 3-condition visual target detection task.

RESULTS

P300 amplitudes were of comparable size in TNAD adolescents and NSAC adolescents. Boys demonstrated larger P3a and P3b amplitudes than girls. Within TNAD, P3b amplitude was reduced in those who drank more frequently, and P3a latency was more prolonged in subjects with higher internalizing symptom counts.

CONCLUSIONS

The P300 deficit was not present in TNAD adolescents without comorbidities. In comparison to results of reduced P300 in treated adolescent AUD samples, this finding likely reflects moderate alcohol exposure, lower genetic vulnerability to alcoholism, and lack of comorbidity in our sample. Further work is needed to determine the relative contributions of these factors to changes in the P300.

Evidence for a Heritable Brain Basis to Deviance-Promoting Deficits in Self-Control

PURPOSE

Classic criminological theories emphasize the role of impaired self-control in behavioral deviancy. Reduced amplitude of the P300 brain response is reliably observed in individuals with antisocial and substance-related problems, suggesting it may serve as a neurophysiological indicator of deficiencies in self-control that confer liability to deviancy.

METHODS

The current study evaluated the role of self-control capacity - operationalized by scores on a scale measure of trait disinhibition - in mediating the relationship between P300 brain response and behavioral deviancy in a sample of adult twins (N=419) assessed for symptoms of antisocial/addictive disorders and P300 brain response.

RESULTS

As predicted, greater disorder symptoms and higher trait disinhibition scores each predicted smaller P300 amplitude, and trait disinhibition mediated observed relations between antisocial/addictive disorders and P300 response. Further, twin modeling analyses revealed that trait disinhibition scores and disorder symptoms reflected a common genetic liability, and this genetic liability largely accounted for the observed phenotypic relationship between antisocial-addictive problems and P300 brain response.

CONCLUSIONS

These results provide further evidence that heritable weaknesses in self-control capacity confer liability to antisocial/addictive outcomes and that P300 brain response indexes this dispositional liability.

Reconceptualizing antisocial deviance in neurobehavioral terms

We propose that neuroscientific understanding of antisocial behavior can be advanced by focusing programmatic efforts on neurobehavioral trait constructs, that is, individual difference constructs with direct referents in neurobiology as well as behavior. As specific examples, we highlight inhibitory control and defensive reactivity as two such constructs with clear relevance for understanding antisocial behavior in the context of development. Variations in inhibitory control are theorized to reflect individual differences in the functioning of brain systems that operate to guide and inhibit behavior and regulate emotional response in the service of nonimmediate goals. Variations in defensive reactivity are posited to reflect individual differences in the sensitivity of the brain's aversive motivational (fear) system. We describe how these constructs have been conceptualized in the adult and child literatures and review work pertaining to traditional psychometric (rating and behaviorally based) assessment of these constructs and their known physiological correlates at differing ages as well as evidence linking these constructs to antisocial behavior problems in children and adults. We outline a psychoneurometric approach, which entails systematic development of neurobiological measures of target trait constructs through reference to psychological phenotypes, as a paradigm for linking clinical disorders to neurobiological systems. We provide a concrete illustration of this approach in the domain of externalizing proneness and discuss its broader implications for research on conduct disorder, antisocial personality, and psychopathy.

Recreational gamblers with and without parental addiction

Research has found that children who have parents with an addiction may be more vulnerable to developing psychopathology compared to children without parental addiction. We compared young adult, recreational gamblers with and without parental addiction on measures of gambling behavior and impulsivity. A total of 286 recreational gamblers (defined as having gambled at least five times in the past 12 months) between the ages of 18 and 29 participated in an initial intake of a longitudinal study assessing susceptibility to pathological gambling. Trained staff members interviewed subjects, and subjects completed cognitive testing and self-report measures. Fifty-three subjects (18.53%) reported at least one parent with an addiction (including alcohol and substance dependence and pathological gambling). Subjects with at least one addicted parent were significantly more likely to report problems resulting from gambling, have significantly greater rates of psychiatric comorbidity, and report significantly more current marijuana and tobacco use. Subjects with an addicted parent were not significantly different on measures of impulsivity. These findings suggest that even at a stage of low-risk gambling, before what has been considered a psychopathology arises, those with a possible environmental and/or genetic risk of addiction exhibit a range of problematic behaviors.

Neurocognitive deficits in male alcoholics: an ERP/sLORETA analysis of the N2 component in an equal probability Go/NoGo task

In alcoholism research, studies concerning time-locked electrophysiological aspects of response inhibition have concentrated mainly on the P3 component of the event-related potential (ERP). The objective of the present study was to investigate the N2 component of the ERP to elucidate possible brain dysfunction related to the motor response and its inhibition using a Go/NoGo task in alcoholics. The sample consisted of 78 abstinent alcoholic males and 58 healthy male controls. The N2 peak was compared across group and task conditions. Alcoholics showed significantly reduced N2 peak amplitudes compared to normal controls for Go as well as NoGo task conditions. Control subjects showed significantly larger NoGo than Go N2 amplitudes at frontal regions, whereas alcoholics did not show any differences between task conditions at frontal regions. Standardized low resolution electromagnetic tomography analysis (sLORETA) indicated that alcoholics had significantly lower current density at the source than control subjects for the NoGo condition at bilateral anterior prefrontal regions, whereas the differences between groups during the Go trials were not statistically significant. Furthermore, NoGo current density across both groups revealed significantly more activation in bilateral anterior cingulate cortical (ACC) areas, with the maximum activation in the right cingulate regions. However, the magnitude of this difference was much less in alcoholics compared to control subjects. These findings suggest that alcoholics may have deficits in effortful processing during the motor response and its inhibition, suggestive of possible frontal lobe dysfunction.

Developmental Endophenotypes: Indexing Genetic Risk for Substance Abuse with the P300 Brain Event-Related Potential

Although substance use disorders are heritable, their complexity has made identifying genes underlying their development challenging. Endophenotypes, biologically informed quantitative measures that index genetic risk for a disorder, are being recognized for their potential to assist the search for disorder relevant genes. After outlining criteria for an endophenotype that includes developmental considerations, we review how the brain P300 response serves as an index of genetic risk for substance abuse and related externalizing disorders. The P300 response is highly heritable and associated broadly with characteristics of externalizing disorder, including childhood disruptive disorders, antisociality, and precocious expression of deviant behavior. This association appears to be mediated by shared genetic influences. Prospective studies confirm that reduced P300 amplitude present in youth prior to significant exposure to addictive substances is associated with the subsequent development of substance use disorders. Despite pronounced change in mean level over the course of development, P300 amplitude shows strong rank order stability with repeated assessment through young adulthood. In addition, P300 developmental trajectories based on multiple assessments show very high heritability and may be especially informative as measures of genetic risk. Collectively, these findings provide strong support that P300 amplitude and its change through development reflect genetic vulnerability to substance abuse and related externalizing psychopathology.

Alcohol effects on cerebral blood flow in subjects with low and high responses to alcohol

BACKGROUND

Although there are multiple indications that alcohol can alter many physiological brain functions, including cerebral blood flow (CBF), studies of the latter have generally used small- or modest-sized samples. Few investigations have yet evaluated how CBF changes after alcohol relate to subsets of subjects with elevated alcoholism risks, such as those with lower levels of response (LR) to alcohol. This study used arterial spin labeling (ASL) after alcohol administration to evaluate a large sample of healthy young men and women with low and high alcohol responses, and, thus, varying risks for alcohol use disorders (AUD).

METHODS

Healthy young adult social drinkers with low and high LR (N=88, 50% women) matched on demography and drinking histories were imaged with whole-brain resting ASL ~1 hour after ingesting ~3 drinks of ethanol and after a placebo beverage (i.e., 178 ASL sessions). The relationships of CBF changes from placebo to alcohol for subjects with low and high LR were evaluated.

RESULTS

CBF increased after alcohol when compared to placebo in 5 frontal brain regions. Despite identical blood alcohol concentrations, these increases with alcohol were less prominent in individuals who required more drinks to experience alcohol-related effects (i.e., had a lower LR to alcohol). The LR group differences remained significant after covarying for recent drinking quantities.

CONCLUSIONS

The results confirm that alcohol intake is associated with acute increases in CBF, particularly in frontal regions. Less intense CBF changes were seen in subjects with a genetically influenced characteristic, a low LR to alcohol, that relates to the future risk of heavy drinking and alcohol problems.

Neural circuitry associated with risk for alcohol use disorders

The core features of risk for alcohol use disorders (AUD), including behavioral disinhibition, affective dysregulation, and executive dysfunction, map onto distinct neural circuits that have been found to be abnormal in the offspring of alcohol dependent individuals. Components of the cerebellothalamocortical system and the extended limbic network may provide the underpinnings for the behavioral and emotional dysfunction observed in individuals at heightened risk for AUD. In addition, abnormalities in these structures appear to be altered in individuals with the predisposition for other psychiatric conditions that may share a similar genetic diathesis. This review proposes several neurobehavioral mechanisms of genetic vulnerability that may account for phenotypic characteristics in individuals at risk for AUD.

Adolescent ethanol exposure: does it produce long-lasting electrophysiological effects?

This review discusses evidence for long-lasting neurophysiological changes that may occur following exposure to ethanol during adolescent development in animal models. Adolescence is the time that most individuals first experience ethanol exposure, and binge drinking is not uncommon during adolescence. If alcohol exposure is neurotoxic to the developing brain during adolescence, not unlike it is during fetal development, then understanding how ethanol affects the developing adolescent brain becomes a major public health issue. Adolescence is a critical time period when cognitive, emotional, and social maturation occurs and it is likely that ethanol exposure may affect these complex processes. To study the effects of ethanol on adolescent brain, animal models where the dose and time of exposure can be carefully controlled that closely mimic the human condition are needed. The studies reviewed provide evidence that demonstrates that relatively brief exposure to high levels of ethanol, via ethanol vapors, during a period corresponding to parts of adolescence in the rat is sufficient to cause long-lasting changes in functional brain activity. Disturbances in waking electroencephalogram and a reduction in the P3 component of the event-related potential (ERP) have been demonstrated in adult rats that were exposed to ethanol vapor during adolescence. Adolescent ethanol exposure was also found to produce long-lasting reductions in the mean duration of slow-wave sleep (SWS) episodes and the total amount of time spent in SWS, a finding consistent with a premature aging of sleep. Further studies are necessary to confirm these findings, in a range of strains, and to link those findings to the neuroanatomical and neurochemical mechanisms potentially underlying the lasting effects of adolescent ethanol exposure.

Neural plasticity, human genetics, and risk for alcohol dependence

Opportunities for advances in the neurobiology of alcohol dependence have been facilitated by the development of sophisticated neurophysiological and neuroimaging techniques that allow us to have a window on developmental changes in brain structure and function. The search for genes that may increase susceptibility to alcohol dependence has been greatly facilitated by the recognition that intermediate phenotypes, sometimes referred to as endophenotypes, may be closer to the genetic variation than is the more complex alcohol dependence phenotype. This chapter will review the evidence that the brain is highly plastic, exhibiting major postnatal changes, especially during adolescence, in neural circuits that appear to influence addiction susceptibility. This chapter will suggest that heritable aspects of brain structure and function that are seen developmentally may be an important endophenotypic characteristic associated with familial risk for developing alcohol dependence. Finally, a review of studies showing associations between brain structural and functional characteristics and specific genes will be offered.

Event-related potentials in clinical research: guidelines for eliciting, recording, and quantifying mismatch negativity, P300, and N400

This paper describes recommended methods for the use of event-related brain potentials (ERPs) in clinical research and reviews applications to a variety of psychiatric and neurological disorders. Techniques are presented for eliciting, recording, and quantifying three major cognitive components with confirmed clinical utility: mismatch negativity (MMN), P300, and N400. Also highlighted are applications of each of the components as methods of investigating central nervous system pathology. The guidelines are intended to assist investigators who use ERPs in clinical research, in an effort to provide clear and concise recommendations and thereby to standardize methodology and facilitate comparability of data across laboratories.

D2 dopamine receptor (DRD2) gene, P300, and personality in children of alcoholics

The D2 dopamine receptor (DRD2) gene has been associated with alcoholism and other drug use disorders. Reduced P300 amplitude has been noted in individuals with psychiatric disorders. Personality variables are also associated with reduced P300 amplitude. The current study was conducted to determine whether variants of the DRD2 would show differential relationships among P300 amplitude and personality traits. The study consisted of 101 adolescent children of alcoholics; 39 carried the A1(+) genotype (A1A1, A1A2) and 62 carried the A1(-) genotype (A2A2). The A1(+) genotype group had higher IQ and Self-Directedness scores than the A1(-) genotype group. As predicted, the negative relationship between Novelty Seeking and Harm Avoidance was present in A1(-) but not A1(+) participants. Additionally, in A1(+) but not in A1(-) participants, there was a negative relationship between Novelty Seeking and Self-Directedness and a positive relationship between P300 amplitude and Cooperativeness. The results suggest that in adolescent children of alcoholics, dopaminergic genetic determinants are critical modifiers of the relationship between neurocognitive and personality endophenotypes proposed as vulnerability markers for substance use disorders.

Deviant P300 amplitude development in males is associated with paternal externalizing psychopathology

Boys at risk for alcoholism show deviant P300 amplitude development. Genetic influences on P300, however, are related to a range of externalizing disorders. This study examined whether P300 development from adolescence to early adulthood differed between groups varying in severity of paternal externalizing. Parietal P300 was assessed during the "rotated heads" task on up to 3 times between the ages of 17 and 24 years. Participants were divided into 3 paternal externalizing groups: (a) severe (father has adult antisocial behavior), (b) intermediate (father has alcohol dependence but not a more severe disorder), and (c) low (father has no externalizing disorders or substance treatment and is not extreme in alcohol use). Mixed models were used to evaluate linear change in amplitude. P300 decreased with age. The severe-risk group had smaller P300 initially and changed less with time than did the low-risk group. The intermediate-risk group did not differ significantly from the low-risk group, but differed marginally from the severe-risk males. Externalizing and early-onset substance disorders in the sons were associated with smaller initial values of P300. Measures of deviant P300 development may be vulnerability markers for externalizing psychopathology.

The role of selected factors in the development and consequences of alcohol dependence

Gender, family history, comorbid psychiatric and substance use disorders, and age all influence a person's risk for alcoholism. In addition, these factors interact with alcoholism to influence neurocognitive functioning following detoxification. This article examines these factors and considers how they interact with each other. This complexity reinforces the need for both animal and human studies and suggests multiple factors that may be sensitive to differential prevention, intervention, and treatment efforts. Thus, it is imperative that hypothesis-driven research designs be directed to identifying the relative potency of these factors and their interactions.

Corpus callosum abnormalities associated with greater externalizing behaviors in subjects at high risk for alcohol dependence

Subjects at high risk for alcoholism have a greater propensity for externalizing behaviors and brain volume reductions of possible neurodevelopmental origin. Morphometric deficits in the corpus callosum (CC), which might reflect this neurodevelopmental abnormality, have been reported in other externalizing disorders such as attention deficit hyperactivity disorder, but not in subjects at high risk for alcoholism. The objective of the current study was to evaluate the CC morphometry in subjects at high risk for alcoholism. Magnetic resonance images of the CC in high-risk subjects (n=20) were compared with those of low-risk subjects matched to the high-risk subjects for age, sex, and handedness (n=20). Mid-sagittal areas of the CC, genu, body, isthmus and splenium were measured based on Witelson's method with good inter- and intra-rater reliability. Externalizing behaviors were assessed using the Semi-Structured Assessment for Genetics of Alcoholism-II. Total CC, genu and isthmus areas were significantly smaller in high-risk than low-risk subjects after controlling for age and intracranial area. The total externalizing symptoms score had a significant negative correlation with genu and isthmus areas. Smaller CC areas and their negative association with externalizing behaviors may represent yet another marker of susceptibility to alcoholism in high-risk subjects.

Neurophysiological mechanisms of emotion regulation for subtypes of externalizing children

Children referred for externalizing behavior problems may not represent a homogeneous population. Our objective was to assess neural mechanisms of emotion regulation that might distinguish subtypes of externalizing children from each other and from their normal age mates. Children with pure externalizing (EXT) problems were compared with children comorbid for externalizing and internalizing (MIXED) problems and with age-matched controls. Only boys were included in the analysis because so few girls were referred for treatment. We used a go/no-go task with a negative emotion induction, and we examined dense-array EEG data together with behavioral measures of performance. We investigated two event-related potential (ERP) components tapping inhibitory control or self-monitoring - the inhibitory N2 and error-related negativity (ERN) - and we constructed source models estimating their cortical generators. The MIXED children's N2s increased in response to the emotion induction, resulting in greater amplitudes than EXT children in the following trial block. ERN amplitudes were greatest for control children and smallest for EXT children with MIXED children in between, but only prior to the emotion induction. These results were paralleled by behavioral differences in response time and performance monitoring. ERP activity was localized to cortical sources suggestive of the dorsal anterior cingulate for control children, posterior cingulate areas for the EXT children, and both posterior cingulate and ventral cingulate/prefrontal regions for the MIXED children. These findings highlight different mechanisms of self-regulation underlying externalizing subtypes and point toward distinct developmental pathways and treatment strategies.

Gray matter volume abnormalities and externalizing symptoms in subjects at high risk for alcohol dependence

Reduced right amygdala volumes have been reported in young, alcohol-naïve subjects at high risk (HR) for alcohol dependence. The differences in brain morphometry have been associated with an excess of externalizing behaviors in these subjects. This may reflect a neurobiological vulnerability to alcohol dependence. Existing Magnetic Resonance Imaging (MRI) studies on these subjects have examined only a few, pre-selected brain regions using the manual regions of interest (ROI) approach. MRI of HR subjects (n = 20) and age, sex, and handedness-matched low-risk (LR) subjects (n = 21) were analyzed using optimized voxel-based morphometry and ROI approach. The externalizing symptoms of these subjects and their fathers were measured using the Semi-Structured Assessment for the Genetics of Alcoholism. HR subjects had significantly smaller volumes of superior frontal, cingulate and parahippocampal gyri, amygdala, thalamus and cerebellum. These gray matter volumes correlated negatively with externalizing symptoms scores. Subjects at HR for alcoholism have reduced volumes of critical areas of brain gray matter, which are associated with increased externalizing symptoms. These represent key endophenotypes of alcoholism.

P3 components and adolescent binge drinking in Southwest California Indians

In adolescence, consuming a large number of drinks over a short interval of time (e.g. binging) is not an uncommon occurrence. Since adolescence is an important neurodevelopmental period, the effect of binge drinking on brain and behavior has become a significant health concern. The present study evaluated event-related potentials (ERPs) in young adult Southwest California Indians who had a history of binge drinking during their adolescence. One hundred twenty five participants who were currently 18-25 yrs of age who were free of Axis I psychiatric diagnoses were categorized as: 1) reporting no binge drinking during adolescence (>5 drinks per occasion before age 18) or drug dependence diagnoses 2) reporting binge drinking during adolescence with no drug dependence diagnoses 3) reporting binge drinking during adolescence and drug dependence diagnoses. ERPs were collected using a facial discrimination task. Adolescent alcohol and drug exposure was found to be associated with decreases in the latency of an early P3 component (P350). Decreases in a later component amplitude (P450) were also found in young adults exposed to alcohol, and those exposed to alcohol and drugs. However, that finding appears to be a combined result of predisposing factors such as family history of alcoholism and presence of other externalizing diagnoses. Taken together these preliminary studies suggests that adolescent binge drinking may result in a decreases in P3 component latencies and amplitudes perhaps reflecting a loss or delay in the development of inhibitory brain systems.

P300 amplitude as an indicator of externalizing in adolescent males

Reduced P300 amplitude is reliably found in individuals with a personal or family history of alcohol problems. However, alcoholism is part of a broader externalizing spectrum that includes other substance use and antisocial disorders. We hypothesized that reduced P300 is an indicator of the common factor that underlies disorders within this spectrum. Community males (N=969) were assessed at age 17 in a visual oddball task. Externalizing was defined as the common factor underlying symptoms of alcohol dependence, drug dependence, nicotine dependence, conduct disorder, and adult antisocial behavior. A robust association was found between reduced P300 amplitude and the externalizing factor, and this relation accounted for links between specific externalizing disorders and P300. Our findings indicate that reduced P300 amplitude is an indicator of the broad neurobiological vulnerability that underlies disorders within the externalizing spectrum.

Heritability of P300 amplitude development from adolescence to adulthood

Early adulthood is a period of late brain development corresponding to the age of onset for psychopathology associated with P300 amplitude reductions. Although amplitude from a single occasion is heritable, little is known about genetic influences on change during this period. This is the first study of P300 change to combine latent growth and twin models. P300 at Pz was measured up to three times at approximately ages 17, 20, and 23 in monozygotic and dizygotic male twins using a visual task. P300 decreased with age. Correlations indexing the stability of amplitude over time were high (median r=.72) and almost 90% of the stable variance (i.e., the model intercept) was attributable to genetic influences. The rate of decrease was heritable, and the genes influencing intercept may be the same ones influencing change. Finally, intercept was more heritable than amplitude at any single time point. Intercept may be a more useful aid in the search for genes associated with relevant psychopathology than single measures of P300. Over a broader age range growth indices may be useful "developmental" endophenotypes.

Heritability and Reliability of P300, P50 and Duration Mismatch Negativity

BACKGROUND

Event-related potentials (ERPs) have been suggested as possible endophenotypes of schizophrenia. We investigated the test-retest reliabilities and heritabilities of three ERP components in healthy monozygotic and dizygotic twin pairs.

METHODS

ERP components (P300, P50 and MMN) were recorded using a 19-channel electroencephalogram (EEG) in 40 healthy monozygotic twin pairs, 19 of them on two separate occasions, and 30 dizygotic twin pairs. Zygosity was determined using DNA genotyping.

RESULTS

High reliabilities were found for the P300 amplitude and its latency, MMN amplitude, and P50 suppression ratio components. ICC=0.86 and 0.88 for the P300 amplitude and P300 latency respectively. Reliability of MMN peak amplitude and mean amplitude were 0.67 and 0.66 respectively. P50 T/C ratio reliability was 0.66. Model fitting analyses indicated a substantial heritability or familial component of variance for these ERP measures. Heritability estimates were 63 and 68% for MMN peak amplitude and mean amplitude respectively. For P50 T/C ratio, 68% heritability was estimated. P300 amplitude heritability was estimated at 69%, and while a significant familiality effect was found for P300 latency there was insufficient power to distinguish between shared environment and genetic factors.

CONCLUSIONS

The high reliability and heritability of the P300 amplitude, MMN amplitude, and P50 suppression ratio components supports their use as candidate endophenotypes for psychiatric research.

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.

Association of DRD4 exon III polymorphism with auditory P300 amplitude in 8-year-old children

OBJECTIVES

The present study was designed to investigate the association between the DRD4 genotype and auditory P300 amplitudes in a high-risk community sample.

METHODS

ERPs were elicited in 197 eight-year-olds (98 boys, 99 girls) using a passive and an active oddball task. Auditory stimuli of 60 dB HL were presented binaurally at 1000 (standard stimulus) and 2000 Hz (target stimulus), at a relative frequency ratio of 80:20. Two trial blocks of 250 stimuli each were collected. P300 amplitudes were analyzed from Fz, Cz and Pz. DNA was genotyped for the DRD4 exon III polymorphism.

RESULTS

A pattern of significant interactions of the DRD4 genotype with gender and experimental conditions was obtained. In both the active and the passive task, boys with at least one copy of the DRD4 7-repeat allele displayed significantly lower P300 amplitudes during the second trial block than boys carrying other alleles.

CONCLUSIONS

This finding provides further evidence supporting a role of P300 amplitude reduction as an endophenotype for disinhibited psychopathology.

P300 development during adolescence: Effects of DRD2 genotype

OBJECTIVE

Young boys at high risk for alcoholism by having a family history of alcoholism (FH+) have lower amplitude of the visual P300 event-related scalp potential. They have also been reported to have a slowing in the rate of P300 amplitude change during adolescence. The present study examined whether the change in P300 amplitude during adolescence in sons of alcoholics and nonalcoholics is affected by D2 dopamine receptor (DRD2) polymorphism.

METHODS

P300 was elicited with a visual discrimination task from 71 adolescent sons of alcoholics and social drinkers (Time 1, T1). The task was readministered 2 years later (Time 2, T2). Comparisons were made between boys who had the DRD2 A1 allele (A1+) and boys who did not (A1-), and between boys with one or both parents being alcoholic (FH+) and boys having no alcoholic parents (FH-).

RESULTS

Discrimination task accuracy was lowest in the highest risk group (A1+, FH+) at T1, and highest in the lowest risk group (A1-, FH-) at T2, producing a significant interaction of allelic group x family history group x session. Reaction time was faster at T2 than T1, and this effect was larger in FH-boys (125 ms) than FH+boys (40 ms). Overall, the behavioral results suggest mild performance deficits on the discrimination task are associated with higher risk for alcoholism. In both testing sessions, P300 attained larger amplitudes in sons of nonalcoholics than sons of alcoholics. At T2 compared to T1, both the latency and amplitude of the P300 were decreased. However, while the developmental P300 latency effect was equivalent in both the A1+ and A1- allelic groups, the P300 amplitude reduction during adolescence, measured both in response to targets and in target minus non-target subtraction waveforms, was only found in boys with the A1- allele.

CONCLUSION

Differences in the developmental course of P300 amplitude over the course of adolescence are dependent on DRD2 polymorphism.

SIGNIFICANCE

These results suggest the importance of genetic determinants of the dopaminergic system in understanding the P300 as a risk marker for substance abuse using an integrative developmental perspective.

Sex-related lateralized effect of emotional content on declarative memory: an event related potential study

Several studies suggest that emotional arousal can promote memory storage. In this study, we evaluated the effects of emotional content on declarative memory, utilizing an adaptation of two versions of the same story, with different arousing properties (neutral or emotional), which have been already employed in experiments involving the enhancing effects of emotions on memory retention. We used event related potentials (ERP) to evaluate whether there is a sex-related hemispheric lateralization of electrical potentials elicited by the emotional content of a story. We compared left and right hemisphere P300 waves, recorded in P3 and P4 electrode sites, in response to emotional or neutral stimuli in men and women. In the left hemisphere, emotional stimuli elicited a stronger P300 in women, compared to men, as indexed by both amplitude and latency measures; moreover, the emotional content of the story elicited a stronger P300 in the right hemisphere in men than in women. The better memory for the arousal material may be related to the differential P300 at encoding. These data indicate that both sex and cerebral hemisphere constitute important, interacting influences on neural correlates of emotion, and of emotionally influenced memory.

The utility of neurophysiological markers in the study of alcoholism

OBJECTIVE

This review attempts to differentiate neuroelectric measures (electroencephalogram (EEG), event-related potentials (ERPs) and event-related oscillations (EROs)) related to acute and chronic effects of alcohol on the brain from those that reflect underlying deficits related to the predisposition to develop alcoholism and related disorders. The utility of these neuroelectric measures as endophenotypes for psychiatric genetics is evaluated.

METHODS

This article reviews the main findings of EEG and ERP abnormalities in alcoholics, offspring of alcoholics at high risk to develop alcoholism and the electrophysiological effects of alcohol on high risk compared to low-risk offspring. It highlights findings using EROs, a fast developing tool in examining brain function and cognition. It also reviews evidence of genetic findings related to these electrophysiological measures and their relationship to clinical diagnosis.

RESULTS

Many of these abnormal neuroelectric measures are under genetic control, may precede the development of alcoholism, and may be markers of a predisposition toward the development of a spectrum of disinhibitory conditions including alcoholism. Genetic loci underlying some neuroelectic measures that involve neurotransmitter systems of the brain have been identified.

CONCLUSIONS

Quantitative neuroelectric measures (EEG, ERPs, EROs) provide valuable endophenotypes in the study of genetic risk to develop alcoholism and related disorders.

SIGNIFICANCE

Genetic studies of neuroelectric endophenotypes offer a powerful strategy for identifying susceptibility genes for developing psychiatric disorders, and provide novel insights into etiological factors.

Spatial-anatomical mapping of NoGo-P3 in the offspring of alcoholics: evidence of cognitive and neural disinhibition as a risk for alcoholism

OBJECTIVE

The concept of disinhibition as a behavioral and biological trait has been considered to be involved in the etiology of alcoholism and its co-existing disorders. The magnitude and functional mapping of event-related potential P3(00) components were analyzed, in order to examine the possible response inhibition deficits in the offspring of alcoholics.

METHODS

The P3 components were compared between 50 offspring of alcoholics (OA) and a matched normal control group (NC) using a visual Go/NoGo task. The low-resolution electromagnetic tomography (LORETA) was used to analyze the functional brain mapping between groups.

RESULTS

The results indicated that the OA group manifested decreased P3 amplitude during the NoGo but not the Go condition compared to the NC group. The voxel-by-voxel analysis in LORETA showed group differences at several brain regions including prefrontal areas during the processing of NoGo but not Go signals.

CONCLUSIONS

The decreased NoGo-P3 suggests that cognitive and neural disinhibition in offspring of alcoholics may serve as a neurocognitive index for a phenotypic marker in the development of alcoholism and related disorders.

SIGNIFICANCE

Dysfunctional neural and response inhibition in the offspring of alcoholics perhaps provides an endophenotypic marker of risk for the development of alcoholism and related disorders.

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.

A genome wide search for alcoholism susceptibility genes

Alcoholism is currently one of the most serious public health problems in the US. Lifetime prevalence rates are relatively high with one in five men and one in 12 women meeting criteria for this condition. Identification of genetic loci conferring an increased susceptibility to developing alcohol dependence could strengthen prevention efforts by informing individuals of their risk before abusive drinking ensues. Families identified through a double proband methodology have provided an exceptional opportunity for gene-finding because of the increased recurrence risks seen in these sibships. A total of 360 markers for 22 autosomes were spaced at an average distance of 9.4 cM and genotyping performed for 330 members of these multiplex families. Extensive clinical data, personality variation, and event-related potential characteristics were available for reducing heterogeneity and detecting robust linkage signals. Multipoint linkage analysis using different analytic strategies give strong support for loci on chromosomes 1, 2, 6, 7, 10, 12, 14, 16, and 17.

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.

Adolescence and the Trajectory of Alcohol Use: Basic to Clinical Studies

Emerging findings from developmentally focused research indicates subtle but important neurocognitive disadvantages among adolescents with alcohol-use disorders (AUD) as compared to teens without AUD. Even after 3 weeks of abstinence AUD youth display a 10% decrement in delayed memory functions. Neuropsychological testing of youth followed at 4 and 8 years demonstrates that heavy drinking during adolescence is associated with diminished retrieval of verbal and nonverbal material, and poorer performance on tests requiring attention skills. Alcohol withdrawal over the teen years appears to uniquely contribute to deterioration in functioning in visuospatial tasks. Brain imaging studies suggest reduced hippocampal volumes, white matter microstructure irregularities, brain response abnormalities while performing challenging cognitive tasks, and enhanced brain response when viewing alcohol cues (i.e., alcohol advertisements) among adolescents with AUD. Family characteristics such as history of alcoholism and socioeconomic status as well as personal features, including adolescent psychopathology, gender, and age of onset must be carefully considered when investigating the influence of teenage drinking on neurocognition. Further research is needed to understand how age at onset of drinking and duration of abstinence at the time of assessment affect cognitive findings. Longitudinal studies are needed to clarify neuromaturational changes associated with early alcohol exposure and patterns of resiliency. Although the magnitude of alcohol-related effects observed in adolescents' neurocognition is relatively modest, the implications are major given the prevalence of alcohol involvement, and the important educational, occupational, and social transitions that occur during adolescence.

Alcohol and the Adolescent Brain

Many people begin to drink alcohol during adolescence and young adulthood. Alcohol consumption during this developmental period may have profound effects on brain structure and function. Heavy drinking has been shown to affect the neuropsychological performance (e.g., memory functions) of young people and may impair the growth and integrity of certain brain structures. Furthermore, alcohol consumption during adolescence may alter measures of brain functioning, such as blood flow in certain brain regions and electrical brain activities. Not all adolescents and young adults are equally sensitive to the effects of alcohol consumption, however. Moderating factors—such as family history of alcohol and other drug use disorders, gender, age at onset of drinking, drinking patterns, use of other drugs, and co-occurring psychiatric disorders—may influence the extent to which alcohol consumption interferes with an adolescent’s normal brain development and functioning.

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.

Differential associations of sex and D2 dopamine receptor (DRD2) genotype with negative affect and other substance abuse risk markers in children of alcoholics

Children of alcoholics have increased risk for substance abuse problems. Self-medication of negative affect may be one developmental path to future substance abuse. Because the 146 young (adolescent) children of alcoholics in the current sample had not used enough abused substances to study substance use directly, the relation of substance abuse risk markers to negative affect was assessed. Because the D2 dopamine receptor (DRD2) A1 allele has been associated with alcoholism and other substance use disorders, negative affect, measured by the Beck Depression Inventory (BDI), was determined in four groups of children: boys and girls with the A1+ allele (A1A1 and A1A2 genotypes) and with the A1- allele (A2A2 genotype). The other risk markers were stress, low amplitude of the P300 evoked potential, poor visuospatial functioning, novelty seeking (NS), and harm avoidance (HA). Stress was correlated with BDI scores in all groups. In contrast, low P300 was associated with BDI scores only in boys with the A1+ allele (P = .04), NS was associated with BDI scores only in girls with the A1+ allele (P = .02), and HA was associated with BDI scores only in boys with the A1- allele (P = .01). In addition, boys with the A1+ allele had lower BDI (P = .05) and HA (P = .005) scores than the respective scores for boys with the A1- allele. Girls with the A1- allele had lower HA scores compared with scores for boys with the A1- allele (P = .02). Girls with the A1+ allele had lower visuospatial functioning than that of boys with the A1+ allele (P<.001). Results indicate that both sex and DRD2 genotype modify associations between negative affect and other substance abuse risk markers.

Substance use disorders, externalizing psychopathology, and P300 event-related potential amplitude

We hypothesize the existence of an inherited predisposition for a spectrum of behaviors and traits characterized by behavioral disinhibition. This externalizing spectrum includes childhood disruptive disorders, antisocial behavior, substance use disorders, personality traits related to behavioral undercontrol, and the precocious expression of problem behavior. We further hypothesize that a genetically influenced central nervous system diathesis underlies this spectrum and is reflected in reduced P300 amplitude in a visual oddball event-related potential task. A review of evidence bearing on the model is derived from findings from the Minnesota Twin Family Study, a population-based, longitudinal investigation of twin youth. These findings indicate that the collection of attributes related to behavioral disinhibition is familial, heritable, and interrelated. Evidence supporting P3 amplitude reduction (P3-AR) as an index of genetic vulnerability for this externalizing spectrum includes its association with (a) familial risk for substance use and antisocial personality disorders, (b) diagnoses of childhood disruptive disorders and substance use disorders, (c) early onset of undersocialized behavior, and (d) quantitative phenotypes related to externalizing problems. In addition, the development of substance use disorders over a 3-year period is associated with P3-AR measured prior to their expression. These findings suggest that P3-AR indexes one aspect of the genetic diathesis for a spectrum of externalizing problem behavior.

Substance abuse-related P300 differences in response to an implicit memory task

The current study examined electrophysiological measures of cognitive efficiency in alcoholics and controls using a negative priming paradigm derived from DeSchepper and Treisman (J. Exp. Psychol. Learn. Mem. Cog. 22 (1996) 27). In this task, sets of novel shapes were presented: Two overlapping green and red shapes on the left and a single white shape on the right. Participants were instructed to ignore the red shape, but to determine whether the green shape was the same as or different from the white shape. On primed trials, previously red (to be ignored; i.e., irrelevant) shapes became green (relevant) shapes in a second component of the task. Participants who were capable of ignoring irrelevant stimuli were expected to experience more difficulty in the primed condition. Therefore, we predicted that, if alcohol-related impairment in cognitive efficiency is due to inability to respond "appropriately" (i.e., ignore irrelevant stimuli), alcoholics would experience less negative priming than normal controls. Both amplitude and latency of the P300 component of the event-related potential were measured in response to each trial condition. Using a 2 x 2 (group x condition) ANOVA with repeated conditions, a significant pattern of group x condition interactions was observed at right frontal, F4 (p=.05) and central parietal, Pz (p=.03) electrode sites on measures of P300 amplitude. A significant group x condition latency interaction was observed at the central parietal electrode, Pz (p=.006). Overall, controls exhibited increased P300 amplitude and latency in response to negatively primed trials. As predicted, alcoholics did not demonstrate this pattern, a finding consistent with alcohol-related cognitive inefficiency.