Semantic processing in alcoholics with and without antisocial symptomatology

Predictors of chronicity in alcohol use disorder: an evoked response potential study

INTRODUCTION

Evoked response potentials (ERP) can reliably map key neurocognitive processes which are putatively responsible for chronic alcohol use disorder (AUD). Aim of the present study was to study P300 auditory odd ball and N400 visual semantic incongruity paradigm mapping executive functions rubric as a potential biomarker predicting chronicity in AUDs. Methodology: 60 right handed 18 to 54 years age subjects were divided into chronic "CAD" and non chronic alcohol dependence "NAD" in addition to healthy control "HC" (N = 30). Subjects were assessed by Addiction Severity Index (ASI), P300 auditory odd ball paradigm in midline region and visual N400 semantic incongruity task in centro-parietal region in a cross sectional design. Results: All the three groups differed significantly for P300 and N400 amplitude in all the leads with maximum attenuation seen in CAD. On discriminant function analysis (DFA), P300 Pz and N 400 C2 amplitude values could accurately classified 78.3% subjects. Composite sensitivity and specificity of the two predictor variables differentiating CAD subjects from NAD were 79.31 and 77.41%. receiver operating characteristic curve generated an area under the curve of .758 and .847 i.e., "fair to good" ability to predict CAD from NAD. Conclusion: We conclude that specific ERP paradigm can be used as a state marker to map the cognitive deficits and as a biomarker to detect chronic AUDs.

Understanding alcohol use disorders with neuroelectrophysiology

Neurocognitive deficits associated with impairments in various brain regions and neural circuitries, particularly involving frontal lobes, have been associated with chronic alcoholism, as well as with a predisposition to develop alcohol use and related disorders (AUDs). AUD is a multifactorial disorder caused by complex interactions between behavioral, genetic, and environmental liabilities. Neuroelectrophysiologic techniques are instrumental in understanding brain and behavior relationships and have also proved very useful in evaluating the genetic diathesis of alcoholism. This chapter describes findings from neuroelectrophysiologic measures (electroencephalogram, event-related potentials, and event-related oscillations) related to acute and chronic effects of alcohol on the brain and those that reflect underlying deficits related to a predisposition to develop AUDs and related disorders. The utility of these measures as effective endophenotypes to identify and understand genes associated with brain electrophysiology, cognitive networks, and AUDs has also been discussed.

Clinical and pathological features of alcohol-related brain damage

One of the sequelae of chronic alcohol abuse is malnutrition. Importantly, a deficiency in thiamine (vitamin B(1)) can result in the acute, potentially reversible neurological disorder Wernicke encephalopathy (WE). When WE is recognized, thiamine treatment can elicit a rapid clinical recovery. If WE is left untreated, however, patients can develop Korsakoff syndrome (KS), a severe neurological disorder characterized by anterograde amnesia. Alcohol-related brain damage (ARBD) describes the effects of chronic alcohol consumption on human brain structure and function in the absence of more discrete and well-characterized neurological concomitants of alcoholism such as WE and KS. Through knowledge of both the well-described changes in brain structure and function that are evident in alcohol-related disorders such as WE and KS and the clinical outcomes associated with these changes, researchers have begun to gain a better understanding of ARBD. This Review examines ARBD from the perspective of WE and KS, exploring the clinical presentations, postmortem brain pathology, in vivo MRI findings and potential molecular mechanisms associated with these conditions. An awareness of the consequences of chronic alcohol consumption on human behavior and brain structure can enable clinicians to improve detection and treatment of ARBD.

Reduced resource optimization in male alcoholics: N400 in a lexical decision paradigm

BACKGROUND

Event Related Potential (ERP) studies have highlighted some measures, notably P3 amplitude, that are associated with both state and trait deficits in alcoholism, while studies examining N400 amplitude in alcoholism are few. The present study aims to examine differences in the N400 component, an electrophysiological correlate of semantic priming, in event-related potentials from a lexical decision task in 87 alcohol dependent subjects and 57 community controls.

METHODS

 Each subject was presented with 300 stimuli sequentially in a quasi-randomized design, where 150 stimuli were words and 150 were non-words. The subjects made a lexical decision indicating the word/non-word status with a button press. Among the words, 50 words (primed) were always preceded by their antonyms (prime, n=50), whereas the remaining 50 words were unrelated. N400 amplitude and latency measures were compiled from ERPs to the primed and unprimed words. Corresponding reaction time (RT) and response characteristics were also analyzed.

RESULTS

Control subjects revealed a significant attenuation of the N400 response to the primed word when compared to the unprimed word. Significantly less attenuation was observed in alcohol dependent subjects. No significant group differences were seen for latency and behavioral measures. All subjects had slower RT for unprimed words compared to primed words; however significantly less RT savings between the unprimed and primed condition was noted for alcoholics.

CONCLUSIONS

 These results suggest a reduced flexibility in the cognitive networks and a lack of resource optimization in alcoholics. The reduced attenuation of N400 during the primed condition in the alcohol dependent subjects may reflect an inability to engage similar neuronal substrates associated with semantic relatedness as seen in the controls. As diminished N400 attenuation during priming is observed in both alcoholics and high risk subjects, it may be a marker of risk and a good endophenotype for alcoholism.

Tobacco Use, Alcohol Dependence, and Cognitive Performance

Chronic alcohol abuse has long been associated with a mild, generalized pattern of cognitive decrements. However, it is important to note that problem drinking rarely occurs in isolation from abuse of other drugs. For people dependent upon alcohol, tobacco is one of the mostly commonly coabused substances. Recent research suggests that individuals with alcohol dependency may gravitate toward tobacco use, in part, because of the positive effects of nicotine on aspects of cognitive performance that may be compromised as a consequence of chronic alcohol misuse. In this article, the author focuses on the effects of nicotine on behavioral and electrophysiological indexes of cognitive performance, and the impact of these effects on alcohol-related cognitive decrements. The author discusses implications of these findings in the context of treatment and recovery of people with alcoholism.

Neurocircuitry in alcoholism: a substrate of disruption and repair

The chronic, excessive consumption of alcohol results in significant modification of selective neural systems of the brain structure, physiology, and function. Quantitative MR structural imaging, diffusion tensor imaging (DTI), and functional MRI (fMRI), together with neuropsychological challenges, have enabled rigorous in vivo characterization of the results of alcoholism on the brain in the human condition. Neuroimaging has also enabled longitudinal study for the examination of alcoholism's dynamic course through periods of drinking and sobriety. Controlled studies have revealed compelling evidence for alcohol-related brain structural and functional modification--some longstanding, some transient, and some compensatory. Patterns of circuitry disruption identified through structural and functional MRI studies suggest a central role for degradation of frontocerebellar neuronal nodes and connecting circuitry affecting widespread brain regions and contributing to alcoholism's salient, enduring, and debilitating cognitive and motor deficits--executive dysfunction, visuospatial impairment, and ataxia.

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.

Visual-spatial attention in alcoholics and illicit stimulant abusers: effects of nicotine replacement

Reports of alcohol or illicit drug-related cognitive impairments have frequently disregarded the potentially confounding effects of smoking status and nicotine withdrawal on these measures. This study addressed this issue by measuring visual-spatial attention via an adaptation of the Posner paradigm in three groups of tobacco smokers: controls without a history of alcoholism or illicit drug use (n=27; 20 male), chronic alcoholics (n=22; 18 male), and illicit stimulant abusers (n=36; 21 male). Throughout testing, nicotine levels were stabilized by the double-blind administration of a high (14 or 21 mg) or low (7 mg) dose transdermal nicotine patch. A significant effect of group was observed for number of correct responses to restriction trials (F=5.48, 2/79 df; p=.006). Performance was normalized in the illicit stimulant group, and alcoholic participants exhibited superior performance relative to both illicit stimulant abusers (p=.002) and controls (p=.01). These findings support the hypothesis that nicotine may have a compensatory or normalizing effect on attentional functions in substance abusers. Whether these results reflect the central nervous system-activating effects of nicotine or merely alleviation of nicotine withdrawal is a topic of ongoing research.