Using Mismatch Negativity to Investigate the Pathophysiology of Substance Use Disorders and Comorbid Psychosis

Substance use disorders (SUDs) have a devastating impact on society and place a heavy burden on health care systems. Given that alcohol, tobacco, and cannabis use have the highest prevalence, further understanding of the underlying pathophysiology of these SUDs is crucial. Electroencephalography is an inexpensive, temporally superior, and translatable technique which enables investigation of the pathobiology of SUDs through the evaluation of various event-related potential components, including mismatch negativity (MMN). The goals of this review were to investigate the effects of acute and chronic alcohol, tobacco, and cannabis use on MMN among nonpsychiatric populations and patients with comorbid psychosis. A literature search was performed using the database PubMed, and 36 articles met our inclusion and exclusion criteria. We found a pattern of attenuation of MMN amplitude among patients with alcoholism across acute and chronic alcohol use, and this dysregulation was not heritable. Reports were limited, and results were mixed on the effects of acute and chronic tobacco and cannabis use on MMN. Reports on comorbid SUDs and psychosis were even fewer, and also presented mixed findings. These preliminary results suggest that MMN deficits may be associated with SUDs, specifically alcohol use disorder, and serve as a possible biomarker for treating these common disorders.

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.

Neurophysiological measures of sensory registration, stimulus discrimination, and selection in schizophrenia patients

Cortical Neurophysiological event related potentials (ERPs) are multidimensional measures of information processing that are well suited to efficiently parse automatic and controlled components of cognition that span the range of deficits exhibited in schizophrenia patients. Components following a stimulus reflect the sequence of neural processes triggered by the stimulus, beginning with early automatic sensory processes and proceeding through controlled decision and response related processes. Previous studies employing ERP paradigms have reported deficits of information processing in schizophrenia across automatic through attention dependent processes including sensory registration (N1), automatic change detection (MMN), the orienting or covert shift of attention towards novel or infrequent stimuli (P3a), and attentional allocation following successful target detection processes (P3b). These automatic and attention dependent information components are beginning to be recognized as valid targets for intervention in the context of novel treatment development for schizophrenia and related neuropsychiatric disorders. In this review, we describe three extensively studied ERP components (N1, mismatch negativity, P300) that are consistently deficient in schizophrenia patients and may serve as genetic endophenotypes and as quantitative biological markers of response outcome.

PASSIVE EVENT-RELATED POTENTIALS BY A SINGLE TONE IN PERSONALITY DISORDERS

A cerebral P3 potential (passive P3) in response to a single tone shares similar morphology to the classical P3 elicited in the active “oddball” paradigm, but reflects passive attention. As patients with schizotypal, antisocial, and borderline personality disorders show reduced amplitude and prolonged latency of classical P3, it is reasonable to expect that these patients might show an abnormal passive P3. We tested whether the single tone elicited event-related potentials (ERPs) in 205 patients with personality disorders and in 30 healthy volunteers. Their Axis I symptoms of depression and anxiety were measured by Zung's Self-rating Depression Scale and Self-rating Anxiety Scale (1965, 1971). Both schizoid and paranoid groups showed significantly reduced P3 amplitude. In addition, the schizoid group showed significantly shortened N1 latency and enhanced N2 amplitude. Most patient groups except schizoids scored higher on the Depression or Anxiety scales, or both, but the ERP findings were not correlated with the Axis I symptoms in any given group alone. The abnormal negative components implied a higher vigilance or cortical arousal level in the schizoid patients, while the reduced P3 amplitude indicated a poorer passive attention in both schizoid and paranoid patients.

Effects of Chronic Alcohol Consumption in a Visual Attention Task and an Auditory Oddball Task: An Event-Related Potential Study

BACKGROUND

In alcohol-dependent individuals changes in brain functioning, as measured with Event Related Potentials (ERP) have been reported.

METHODS

In the present study a visual attention and an auditory oddball task were used to investigate possible differences between light, moderate, and heavy social drinkers and excessive drinkers. It was hypothesized that with increasing alcohol intake an increasing number of ERP components elicited in the visual attention task and the auditory oddball task would show diminished amplitudes.

RESULTS

No differences were found between light, moderate, and heavy social drinkers. A trend for a smaller P3 amplitude in the visual attention task was found when comparing the alcohol-dependent participants with the light social drinkers. It is argued that this difference might be an effect of alcohol dependence and/or a reflection of possible unknown or undetected family history of alcohol-related disturbances.

CONCLUSIONS

In the current study, even at rather large amounts of regular alcohol intake, no evidence was found for any toxic effect of social alcohol use neither in a visual attention task nor in an auditory oddball task.

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.

Mismatch negativity: no difference between controls and abstinent alcoholics

BACKGROUND

A number of studies have examined the amplitude of the mismatch negativity (MMN) evoked potential as a measure of a brain inhibitory deficit in alcoholics or those at risk for alcoholism. The current study examined MMN in alcoholics abstinent an average of 6.7 years (with a minimum of six months abstinence) compared to controls. This study examined the association of MMN with alcoholism family history density, with indices of the presence and severity of externalizing disorders (a risk-factor for alcoholism), and with alcohol use variables.

METHODS

Electroencephalograms were gathered on 76 subjects (38 controls, 38 abstinent alcoholics) during a nonattending mismatch negativity experiment. Measures of alcoholism family history density, disinhibited personality traits, and antisocial symptoms served as measures of risk-factors known to be associated with a genetic liability to alcoholism. Alcohol use variables were used as measures of alcoholism severity.

RESULTS

There were no differences in MMN amplitude or latency between controls and abstinent alcoholics. There also were no significant associations between MMN measures and the measures of risk for alcoholism or with the severity of alcohol use or duration of abstinence.

CONCLUSIONS

The results suggest that MMN is neither affected in chronic alcoholics nor associated with alcoholism vulnerability, and thus does not reflect a trait marker of alcoholism or alcoholism risk. The current results do not address effects on MMN of acute alcohol ingestion or withdrawal from alcohol.

Attention and selection in the growing child: views derived from developmental psychophysiology

Our understanding of developmental changes in attentional selection in the growing child has been advanced substantially by the results of (a relatively small number of) studies undertaken from a psychophysiological perspective. The basic outcome of these studies is that, in attentional filtering as well as selective set (the two basic paradigms in attention research), the processes necessary for attentional selection are in essence available even to the young child; however, the speed and efficiency of these processes tends to increase as the child grows into an adolescent. Under optimal conditions, filtering is performed at early stages of information processing, but less optimal stimulus characteristics and task requirements may induce a shift in the locus of selection to later processing stages for young children whereas older individuals are better able to preserve their early locus of selection. When early selection is constrained, young children are substantially more sensitive to the adverse effects of response competition. In selective set, sub-optimal conditions lead not so much to a shift in locus of selection processes, but to a shift in the age at which asymptote efficiency is attained. We have proposed hierarchical regression analysis as a useful technique to examine whether age-related differences in attention effects, as observed in specific ERP components and in RT, are reflections of an age effect on a single source of attentional selection or of separate sources that each contribute uniquely to the developmental trends seen in (attention effects on) RT. Re-analyses of existing data demonstrated that (again depending on task specifics) many but not all of the different component processes involved in attentional selection contributed unique variance to the age-related changes in attention effects.

Visual P3a in male subjects at high risk for alcoholism

BACKGROUND

Voltage of the P300 component of event-related potentials (ERPs) has been proposed as a phenotypic marker of risk for alcoholism. P3a elicited by intrusive events is important in the context of deficits in inhibition found during psychophysiological and behavioral evaluations in children of alcoholics.

METHODS

ERPs were recorded from a group of adult children of alcoholics (n = 26) and controls (n = 23) with a three-stimulus visual oddball paradigm. The task required a difficult perceptual discrimination between a frequent (.80) vertical line and an infrequent (.10) 2 degrees tilted line (target). An easily discriminable nontarget infrequent horizontal line also occurred (.10). Subjects were required to press a button to the target. P3a was compared using mixed-model ANCOVAs at 31 sites organized in 5 scalp regions. Current source density (CSD) maps were also analyzed.

RESULTS

High-risk (HR) subjects manifested reduced P3a amplitudes compared to controls at frontal, central, parietal, and temporal electrodes. CSD analyses supported these findings with group differences found for all the scalp regions.

CONCLUSIONS

The results are discussed in relation to previous HR studies. P3a reductions may be related to deficits in neuronal inhibition during stimulus processing. These results suggest that P3a amplitude may be important as a marker for vulnerability to alcoholism.

Mismatch negativity in young children of alcoholics from high-density families

The mismatch negativity (MMN) component of event-related potentials was recorded from a group of young children of alcoholics (n = 19, 8 females) with a high-density family history of alcoholism and from a control group (n = 23, 12 females), between 8 and 15 years of age. A dichotic listening task was used, and subjects had to pay attention to an oddball paradigm in one ear and ignore the stimuli in the other ear. The event-related potentials elicited by the standard unattended tones were subtracted from those elicited by the infrequent deviant unattended tones, and the MMN was measured at 10 frontal and central electrodes. No group differences were observed in peak latency, peak amplitude, and mean amplitude of the MMN. These results indicated that preattentive mechanisms of mismatch detection were not impaired in young subjects at high risk for alcoholism. Results are discussed in relation to differences in electrophysiological indexes of automatic versus controlled information processing and in relation to the characteristics of the sample.