Evoked brain potential deficits in alcoholism and aging

Neural correlates of visuoperceptive changes in severe alcohol use disorder: A critical review of neuroimaging and electrophysiological findings

Visuoperceptive deficits are frequently reported in severe alcohol use disorder (SAUD) and are considered as pervasive and persistent in time. While this topic of investigation has previously driven researchers' interest, far fewer studies have focused on visuoperception in SAUD since the '90s, leaving open central questions regarding the origin and implications of these deficits. To renew research in the field and provide a solid background to work upon, this paper reviews the neural correlates of visuoperception in SAUD, based on data from neuroimaging and electrophysiological studies. Results reveal structural and functional changes within the visual system but also in the connections between occipital and frontal areas. We highlight the lack of integration of these findings in the dominant models of vision which stress the dynamic nature of the visual system and consider the presence of both bottom-up and top-down cerebral mechanisms. Visuoperceptive changes are also discussed in the framework of long-lasting debates regarding the influence of demographic and alcohol-related factors, together stressing the presence of inter-individual differences. Capitalizing on this review, we provide guidelines to inform future research, and ultimately improve clinical care.

Persistence of Neuronal Alterations in Alcohol-Dependent Patients at Conclusion of the Gold Standard Withdrawal Treatment: Evidence From ERPs

Background: One of the main challenges for clinicians is to ensure that alcohol withdrawal treatment is the most effective possible after discharge. To address this issue, we designed a pilot study to investigate the efficacy of the rehabilitation treatment on the main stages of information processing, using an electroencephalographic method. This topic is of main importance as relapse rates after alcohol withdrawal treatment remain very high, indicating that established treatment methods are not fully effective in all patients in the long run. Method: We examined in alcohol-dependent patients (ADP) the effects of the benzodiazepine-based standard detoxification program on event-related potential components at incoming (D0) and completion (D15) of the treatment, using tasks of increasing difficulty (with and without workload) during an auditory oddball target paradigm. Untreated non-alcohol-dependent-volunteers were used as matching controls. Results: At D0, ADP displayed significantly lower amplitude for all ERP components in both tasks, as compared to controls. At D15, this difference disappeared for the amplitude of the N1 component during the workload-free task, as well as the amplitude of the P3b for both tasks. Meanwhile, the amplitude of the N2 remained lower in both tasks for ADP. At D0, latencies of N2 and P3b in both task conditions were longer in ADP, as compared to controls, whilst the latency of N1 was unchanged. At D15, the N2 latency remained longer for the workload condition only, whereas the P3b latency remained longer for the workload-free task only. Conclusion: The present pilot results provide evidence for a persistence of impaired parameters of ERP components, especially the N2 component. This suggests that neural networks related to attention processing remain dysfunctional. Longitudinal long-term follow-up of these patients is mandatory for further assessment of a link between ERP alterations and a later risk of relapse.

Neurophysiological correlates of moderate alcohol consumption in older and younger social drinkers

BACKGROUND

Nearly 40% of adults aged 65 and older in the United States consume alcohol. Research in older adults has largely examined potential health effects of a moderate drinking lifestyle. Examination of acute effects in this population is generally lacking. To investigate alcohol-induced alteration of electrophysiological correlates of attention in this population, we employed a covert attentional task. We hypothesized that moderate alcohol administration as well as older age would reduce P3 amplitude and increase latency. We anticipated an interaction such that, relative to their age-matched controls, older adults receiving alcohol would be more affected than their younger counterparts.

METHODS

Participants included healthy older (aged 50 to 67; n = 20; 9 men) and younger (aged 25 to 35; n = 12; 5 men) moderate drinkers. Participants received either a moderate dose of alcohol (breath alcohol concentration ~50 mg/dl) or a placebo beverage. Following absorption, the task was administered and neurophysiological measures were obtained. P3 amplitude and latency were separately subjected to ANOVA across cue conditions using age and dose as independent variables.

RESULTS

As predicted, P3 amplitude in older adults was significantly lower than in younger adults across cue conditions. An age by alcohol interaction was detected, revealing that older adults receiving alcohol showed lower P3 amplitudes than any other group. An age effect for P3 latency was found, with older adults having longer latencies than their younger counterparts. A significant age by alcohol interaction for P3 latency was detected, revealing that older adults receiving alcohol displayed delayed P3 latencies relative to older adults receiving placebo. In contrast, younger adults receiving alcohol had reduced latency compared to those receiving placebo, although this effect did not reach significance.

CONCLUSIONS

Results suggest that older adults demonstrated alcohol-related shifts in P3 characteristics during an intentional attention task, whereas younger adults failed to demonstrate this pattern.

Alcohol: effects on neurobehavioral functions and the brain

Alcoholism results from an interplay between genetic and environmental factors, and is linked to brain defects and associated cognitive, emotional, and behavioral impairments. A confluence of findings from neuroimaging, physiological, neuropathological, and neuropsychological studies of alcoholics indicate that the frontal lobes, limbic system, and cerebellum are particularly vulnerable to damage and dysfunction. An integrative approach employing a variety of neuroscientific technologies is essential for recognizing the interconnectivity of the different functional systems affected by alcoholism. In that way, relevant experimental techniques can be applied to assist in determining the degree to which abstinence and treatment contribute to the reversal of atrophy and dysfunction.

Chronic effects of social drinking in a card-sorting task: an event related potential study

OBJECTIVE

The Wisconsin Card Sorting Task (WCST) is one of the most widely used neuropsychological tests of frontal lobe function, which is thought to be affected by regular alcohol use. The present study used a computer-adapted version of the WCST to assess the effects of chronic alcohol consumption on the brain.

METHODS

Participants (N=59) sorted cards according to an initially unknown sorting rule, which referred to shape, number, or color. The correctness of the chosen sorting rule was indicated by a feedback stimulus. This correct sorting rule had to be followed for a number of stimuli, and when it changed participants had to find out which rule had to be followed next. A distinction was made between early (correct sorting rule is unknown) and late trials (correct sorting rule is known and applied). To measure brain activity related during the task event related potentials (ERPs) were recorded to the target and feedback stimulus in light (N=14), moderate (N=16) and heavy (N=19) social drinkers and excessive alcohol users (N=10).

RESULTS

No differences in number of series completed or the reaction time in each trial, were found between the four groups. In contrast, a mid-frontal N1 component in reaction to the feedback stimuli did reveal differences between the four groups. In the light and moderate drinkers, on early feedback trials the N1 was larger relative to late feedback trials, but this effect was absent in the heavy social drinkers and excessive drinkers.

CONCLUSIONS

The reduced N1 effect with increasing alcohol intake could reflect abnormal allocation of attention or impaired conflict monitoring, possibly based on activity in the anterior cingulate cortex.

SIGNIFICANCE

Heavy social drinking and excessive drinking leads to changes in the mid-frontal N1 during feedback trials of the WCST.

A study of event-related potential-P3 characteristics in children of alcoholics

Auditory P3 characteristics were studied in children (aged 8-14 years) of male alcoholics without psychiatric problems and children of normal parents employing an oddball auditory paradigm. All the children of alcoholics were from families with multiple cases of alcoholism (each child had an average of 4.3 first- and second-degree relatives including the father, meeting criteria for alcoholism). Subjects were presented with high and low pitched tones with global probabilities of 25% and 75% of total trials, respectively. The amplitude of P3 component was significantly reduced in high-risk children (p < 0.001). Implications of the findings, including the role of P3 as biologi cal marker of risk for alcoholism, are discussed.

Alterations in cortical visual evoked response following ethanol feeding in adult rats

A study was performed on the visual-evoked response (VER) in adult rats that were given an ethanol containing liquid diet for 2 months and examined directly after the exposure period or subjected to a gradual decrease in ethanol over 3 days and total abstinence for 1 week. Control rats showed a first negative peak (N1) directly following the first positive peak (P1). In ethanol-exposed rats examined without withdrawal, the VER showed an increase in onset latency and a marked distorsion of the N1 region. The existing N1 potential was very sensitive to high-frequency stimulation. The alterations were partly normalized 1 week after withdrawal. There was no increase in latency to onset of the response or to P1. There remained an increase of latency and a reduced relative amplitude upon high-frequency stimulation of the N1 peak in ethanol-exposed rats compared with controls. The mechanisms underlying the changes in the cortical potentials are not clear, but they may be related to the cholinergic, glutamatergic/NMDA and/or noradrenergic cortical systems. The lack of persistent changes in onset and P1 latency may be related to the circumstance that the retinogeniculate impulses are transmitted over glutamatergic kainate receptors, which are relatively resistant to ethanol.

Event-related potential evidence of dysfunction in automatic processing in abstinent alcoholics

The preattentive automatic processing of 63 alcoholics and 27 controls was evaluated with an auditory inattentive event-related oddball paradigm. We examined the mismatch negativity and the N2-P3 complex. Results showed significantly greater amplitude for N2, P3 and the N2-P3 complex for controls but no individual lead (Fz, Cz, Pz) differences by group. A group-by-lead interaction was found for N2 and for the N2-P3 complex. There were no significant latency differences between groups; however, a significant age-by-group interaction effect on latency was greatest at the Cz electrode. Results reflect a possible aberration of automatic processing in alcoholics because of a defect in the mnemonic template necessary to match with an infrequent deviant stimuli. We also found suggestive evidence of a relative weakness of frontal cortical organization in alcoholics. Future studies are suggested that would help clarify these differences in alcoholics.

Acute effects of ethanol on pattern reversal and flash-evoked potentials in rats and the relationship to body temperature

The effects of acute ethanol treatment on flash and pattern reversal visual evoked potentials (FEPs and PREPs, respectively) were examined in three experiments using Long-Evans rats. The relationships of evoked potential parameters with blood ethanol concentration and body temperature were examined. In Experiment 1, rats were treated i.p. with vehicle or 0.5, 1.0 or 2.0 g ethanol/kg body weight, and tested 30 min later. The 2.0 g/kg group had prolonged latencies of PREP peaks, no changes in PREP peak-to-peak amplitudes, and lower body temperatures than saline-treated controls. The peak latency shifts were significantly correlated with both blood ethanol concentration and body temperature, and were of a magnitude to be expected from similar changes in body temperature alone. Experiment 2 measured both PREPs and paired-flash FEPs in rats 30 min after injection of either 0, 0.5 or 2.0 g/kg ethanol. PREP changes were found following treatment with the high dose which were similar to those of Experiment 1. Some FEP peak latencies were prolonged and peak-to-peak amplitudes were reduced by both doses of ethanol, despite the fact that body temperatures were reduced at only the high dose. At 2.0 g/kg ethanol, the FEP changes in latency, but not amplitude, were in accordance with what would be expected from body temperature changes alone. The third study attempted to investigate the role of reduced body temperature in producing the visual evoked potential changes by testing at room temperatures of 22 or 30 degrees C. Contrary to expectations, the rats receiving 2 g/kg ethanol were approx. 1 degree C cooler than controls at both room temperatures. Evoked potential latencies were greater in ethanol-treated rats than controls at both room temperatures. There were no significant effects of ethanol on FEP amplitudes. Overall, the effects of low doses of ethanol were independent of temperature changes, but the effects of higher doses of ethanol (2.0 g/kg) could not be distinguished from those produced by differences in body temperature alone.

Alcohol, head injury, and neuropsychological function

Evidence is reviewed indicating that the extent of alcohol abuse alone cannot account for the neuropsychological deficits observed in alcoholics, and that alcohol abuse and head injury may interact in some patients to influence neuropsychological status. Alcohol abuse both increases the risk for head trauma and potentiates the resulting brain injury, which can lead to negative neuropsychological consequences. Clinicians involved in the treatment of addiction should assess patients for history of head injury, and neuropsychological deficits consequent to both head injury and ethanol. These deficits may limit patient ability to comply with addiction rehabilitation programs. Conversely, clinicians in acute care and rehabilitation of the sequelae of head trauma should routinely assess their patients for substance abuse, because such abuse can have a significant impact on recovery from brain injury.

Multimodality exploration of event-related potentials in chronic alcoholics

Short- and long-latency auditory evoked potentials (SAEPs and LAEPs), visual-evoked potentials (VEPs), and contingent negative variation (CNV) were studied in 32 chronic alcoholics and their age-, sex-, and education-matched control subjects. The alcoholics exhibited a delayed SAEP peak V and an increase in the III-V and I-V intervals, increased VEP P100 latency, increased LAEP N2 and P3 latencies and increased LAEP N1-P2 amplitude. The analysis of the anomalies at a clinical level indicates a differential sensitivity of the event-related potentials. The parameters most sensitive to chronic alcohol consumption were (in descending order) P3 latency, peak V latency, the I-V and III-V intervals, and P100 latency.

rHuEPO treatment improves brain and cognitive function of anemic dialysis patients

Twenty-four patients with chronic renal failure, stabilized on hemodialysis, were treated with recombinant human erythropoietin. Before treatment, all patients were anemic (mean Hct = 23.7%). Hematocrits reached normal levels (36.5%) after three months of treatment. Brain event-related potentials and neuropsychological tests were used to assess changes in brain and cognitive functions associated with the correction of anemia. Assessments were done prior to and after three and twelve months of rHuEPO treatment. The P3 component of the event-related potential increased in amplitude significantly with treatment, while its latency was unaffected. Of the four neuropsychological tests administered, scores on two improved significantly with treatment, and the other two approached significance. Taken together, these findings suggest that the correction of anemia to hematocrits near normal in uremic patients by rHuEPO treatment improves brain and cognitive function by raising levels of sustained attention, thus increasing speed and efficiency of scanning and perceptual-motor functions and enhancing learning and memory. These findings also suggest that anemia, either directly or indirectly, may impair brain function.

Cognitive function, mood and P3 latency: effects of the amelioration of anemia in dialysis patients

Attention difficulties and psychomotor slowing associated with depressed mood affect the ability of individuals to perform on most neuropsychological tests. It has been suggested that latency of the P3 (P300) component of the event-related EEG potential is an index of neurocognitive status which is not affected by mood. Dialysis patients, who experience diminished dysphoric mood with the reversal of anemia when treated with recombinant human erythropoietin (rHuEPO), were tested for neurocognitive performance, mood and latency of P3. Prior to rHuEPO treatment mood was dysphoric, and neurocognitive testing showed mild deficits, but P3 latency was normal. After treatment, mood improved and neurocognitive test performance was normal. P3 amplitude increased over frontal areas, while P3 latency remained unchanged. Thus, in the case of dysphoric mood, P3 latency may provide a more accurate index of cognitive capacity (as opposed to level of functioning) than neurocognitive test measures.

Risk markers for alcoholism in high-density families

This review summarizes the efforts of our research program to identify markers for alcoholism risk, which broadly fall within the domain of temperament and those which may be described as attentional or information-processing capacities. Analyses of three-generation pedigrees that include minor children at higher risk of becoming alcoholic indicate that event-related potential characteristics differ between high- and low-risk children. Newer results concerning cardiac responsivity both in minor children and adult high-risk individuals are presented. These results suggest a relationship between personality or temperament on the one hand, and cardiac responsivity on the other. Additional neurobehavioral markers are addressed including static ataxia. Recent segregation analyses and linkage to particular DNA segments are also included.

Event-related potential characteristics in children of alcoholics from high density families

Sons and daughters (ages 8-14) of male alcoholics without psychiatric problems were compared with sons and daughters of controls employing two auditory paradigms to elicit event-related potentials (ERPs). All of the children of alcoholics were from high density families (each father had an average of 3.7 first and second-degree relatives meeting criteria for alcoholism). Subjects were presented with high- and low-pitched tones with global probabilities of 25% and 75% of total trials, respectively. Subjects were instructed to count silently the number of "high" tones (rare targets) but not the number of "low" tones (non-targets) and report the number heard. In a second auditory paradigm (Choice Reaction task), subjects were asked to perform a different motor response to each high or low tone. The amplitude of the P300 component was influenced significantly by event probability (decreased amplitudes were associated with increased event probability). A greater rate of decrease in P300 amplitude occurred among the high risk children as event probability increased. In addition, greater negativity beginning at approximately N250 was observed for both tasks at the frontal electrode for the high risk children as compared to controls. This enhanced frontal negativity is interpreted in terms of a maturational lag hypothesis.

Event-related potentials as markers for alcoholism risk in high density families

One hundred sixty-eight adult siblings and parents from affected and control families were tested for ERP characteristics using two tasks involving an auditory oddball paradigm. Significant within family differences among affected families suggest that risk for developing alcoholism may be seen even in adult subjects who have had experience consuming alcohol. Further, analysis of quantity and recency of drinking in the past seven days were not correlated with either amplitude or latency of P300, suggesting that the within-family differences observed reflect relative risk for developing alcoholism rather than experience with alcohol.

Late event-related potential changes in alcoholics

The P3 component of the event-related potential (ERP) was recorded during a Go/No-Go task from 42 alcoholic subjects, abstinent for 11-63 days, and 66 normal adult volunteers. In two different tasks, ERPs were elicited by visually presented words which provided explicit response instructions to Go (PUSH) or No-Go (WAIT). In the Noise Task, half of both Go and No-Go stimuli were degraded with ampersands (&P&U&S&H&, &W&A&I&T&). In the Probability Task, the probability of the Go stimulus was 25% and No-Go 75% on one run and the proportion reversed on another run. For both tasks, the amplitude of alcoholics' P3 was smaller than that of controls to the Go but not to the No-Go stimulus. There was a similar, but less pronounced trend for P3 latency to be delayed in alcoholic subjects for the Go, but not No-Go stimuli for the Noise Task. The P3 changes in alcoholics are consistent with those seen in several disease states which produce cognitive impairment.

Cognitive deficits related to memory impairments in alcoholism

Cognitive impairments related to alcoholism are examined in terms of input, intervening, and output variables. Respectively, the dysfunctions are represented by visuospatial/perceptual abnormalities, affective/conative deficits, and strong perseverative response tendencies. Defects in one or more of these aspects of cognitive functioning may appear as problems of memory. Functional differences between subgroups of alcoholics who do and do not develop severe anterograde amnesia characteristic of Korsakoff's syndrome presumably are attributable to differences in the distribution and extent of brain pathology. Both subgroups have widespread cortical pathology, which may play an important role in stimulus-processing deficiencies observed in both. Korsakoff's have demonstrated a more significant degree of pathology in diencephalic and basal forebrain structures than that observed in non-Korsakoff alcoholics; this may contribute to the greater memory and affective impairments in the former. However, in no subgroup of alcoholics can a single functional system or brain region be implicated as the major contributory factor. Rather, damage to multiple brain regions likely is responsible for the plethora of cognitive difficulties reported in the alcoholism literature.

Behavioral effects of alcohol in sons of alcoholics

This paper describes a search for genetically mediated biological factors that contribute to a predisposition toward alcoholism. Healthy, nonalcoholic, drinking men aged 21 to 25 who have a close alcoholic relative were selected as the family history positive (FHP) or higher risk subjects and matched with lower risk controls (family history negative, or FHN) on demography, drinking and smoking history, and height to weight ratio. Comparisons of this higher and lower risk population revealed no significant differences in selected personality attributes, and an alcohol challenge resulted in identical patterns of blood alcohol over time. However, the FHP men developed higher levels of the first breakdown product of ethanol, acetaldehyde, after drinking, demonstrated a less intense intoxication than the FHN controls despite identical blood alcohol concentrations, and tended to show a lower amplitude of a positive brain wave sent at about 300 msec in an event-related potential paradigm. These results may be clues to help investigators identify genetic markers of a predisposition toward alcoholism.

Neurobiological relationships between aging and alcohol abuse

Both biological aging and chronic exposure to alcohol may cause impaired learning and memory in man and animals. The chains of processes beginning with molecular changes that in turn alter electrophysiology and morphology and finally culminate in changes of behavior (individual and social) are largely unknown. While these chains originating with molecular events leading to the same behavioral end result may be totally different, they may also overlap at any one of these levels of biological organization, accentuate, attenuate each other, to branch again and to develop parallel to each other. There is currently some evidence from observations in humans and animals that both aging and chronic alcohol toxicity induce the following changes: brain atrophy measured in vivo by computerized tomography, histological loss of the dendritic tree of neurons in various brain regions including hippocampus and cerebellum, and a variety of chemical changes of brain synaptic function, such as loss of benzodiazepine receptors.

Age and alcoholism: independent memory decrements

Similarities and differences in performances on 18 verbal and nonverbal memory tasks were studied in young and old alcoholics and in young and old controls as test of hypotheses postulating that cognitive decrements from alcoholism either mimic "premature aging," are "age sensitive," or are "independent" from those of normal aging. Young and old alcoholics were matched in length and rate of heavy drinking and were also equated with their controls in age, education, and vocabulary. The multivariate memory and decision data, when converted to independent factor scores, separated alcoholic from control groups on a factor reflecting memory for auditorily presented information. This was independent from factor scores affected mainly by age, such as memory for visuospatial items or decision bias. Age and alcoholism produced overlapping but distinctly different profiles of memory impairments. Decrements in young alcoholics did not resemble those of aging nor did old alcoholics surpass old controls in any but one factor, so that neither the premature aging nor the age sensitivity hypothesis were invariably supported.

Alcohol consumption and premature aging. A critical review

Research conducted during the past ten years has demonstrated that alcoholics resemble yet older nonalcoholics on a variety of behavioral, radiological, electrophysiological, and regional blood flow measures of brain function. These similarities have led to speculation that excessive alcohol consumption causes a premature aging of the brain that, in turn, is responsible for the characteristic structural and functional changes seen in detoxified alcoholics. In this chapter, we discuss some of the conceptual and methodological problems associated with what has become known as the premature-aging hypothesis and review a series of recent studies that have used neuropsychological, computerized-tomography, and evoked-potential techniques to test its validity. We conclude that there is very little compelling empirical support for this intriguing hypothesis and suggest that the neurobehavioral changes seen in alcoholics are merely the reflection of a diffusely distributed pattern of brain damage.