Effects of chronic alcoholism on hemispheric functioning: an examination of gender differences for cognitive and dichotic listening tasks

Visuoperceptive Impairments in Severe Alcohol Use Disorder: A Critical Review of Behavioral Studies

The present literature review is aimed at offering a comprehensive and critical view of behavioral data collected during the past seventy years concerning visuoperception in severe alcohol use disorders (AUD). To pave the way for a renewal of research and clinical approaches in this very little understood field, this paper (1) provides a critical review of previous behavioral studies exploring visuoperceptive processing in severe AUD, (2) identifies the alcohol-related parameters and demographic factors that influence the deficits, and (3) addresses the limitations of this literature and their implications for current clinical strategies. By doing so, this review highlights the presence of visuoperceptive deficits but also shows how the lack of in-depth studies exploring the visual system in this clinical population results in the current absence of integration of these deficits in the dominant models of vision. Given the predominance of vision in everyday life, we stress the need to better delineate the extent, the specificity, and the actual implications of the deficits for severe AUD.

DNA methylation of dopamine-related gene promoters is associated with line bisection deviation in healthy adults

Handedness and language lateralization are the most investigated phenotypes among functional hemispheric asymmetries, i.e. differences in function between the left and the right half of the human brain. Both phenotypes are left hemisphere-dominant, while investigations of the molecular factors underlying right hemisphere-dominant phenotypes are less prominent. In the classical line bisection task, healthy subjects typically show a leftward attentional bias due to a relative dominance of the right hemisphere for visuospatial attention. Based on findings of variations in dopamine-related genes affecting performance in the line bisection task, we first tested whether DNA methylation in non-neuronal tissue in the promoter regions of DBH, SLC6A3, and DRD2 are associated with line bisection deviation. We replicated the typical behavioral pattern and found an effect of DNA methylation in the DBH promoter region on line bisection deviation in right-aligned trials. A second exploratory analysis indicated that an overall DNA methylation profile of genes involved in dopamine function predicts line bisection performance in right-aligned trials. Genetic variation in dopamine-related genes has been linked to attention deficit hyperactivity disorder (ADHD), a neurodevelopmental trait associated with rightward attentional bias. Overall, our findings point towards epigenetic markers for functional hemispheric asymmetries in non-neuronal tissue not only for left hemisphere-dominant, but also for right hemisphere-dominant phenotypes.

Sex differences in alcohol-related neurobehavioral consequences

In this chapter, we review existing research regarding sex differences in alcohol's effects on neurobehavioral functions/processes. Drawn largely from laboratory studies, literature regarding acute alcohol administration and chronic alcohol misuse is explored focusing on commonly employed neuropsychologic domains (e.g., executive function, visuospatial skills, learning and memory, gait and balance), neurophysiologic measures (e.g., electroencephalography and event-related potentials), and structural and functional neuroimaging (e.g., magnetic resonance imaging (MRI), functional MRI, diffusion tensor imaging, positron emission tomography, and magnetic resonance spectroscopy). To provide a historical perspective on the development of these questions, we have included reference to early and more recent research. Additionally, specific biases, knowledge gaps, and continuing controversies are noted.

An Investigation of Vetrbal Spatial Functioning in Chronic Alcoholics

The mild generalized brain dysfunction hypothesis of alcoholic impairment predicts that, as a group, alcoholics will be impaired on both right- and left-hemisphere spatial functioning tests. A verbal-spatial problem-solving task (Luria, 1980) composed of explicitly spatial problems and comparative problems was developed and administered along with a well-known visual spatial problem-solving task (Block Design) to 24 sober male alcoholics and 24 peer controls. As expected, alcoholics performed more poorly and made more configurational errors than controls on Block Design. In accord with the mild generalized hypothesis, alcoholics performed more poorly than peer controls on the more explicitly spatial verbal problems, but not on the easier comparative problems.

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.

Performance of Psychotic and Substance Abuse Patients With or Without Head Injury on the Halstead-Reitan Battery

Performances of patients diagnosed with psychosis or substance abuse disorder were evaluated using the Halstead-Reitan Neuropsychological Test Battery (Reitan & Wolfson, 1993) and the General Neuropsychological Deficit Scale (GNDS). Half of the participants in each group had a documented head injury that required medical attention. Differences between patient groups with head injury was not significantly above those without head injury on the Halstead-Reitan subtests or the GNDS. Average performance in all 4 groups was in the mild to moderate impairment range according to established norms and, depending on the group, with 80% to 93% of patients scoring above the accepted cutoff for impairment on the GNDS. This study has implications for referrals attempting to distinguish head injury effects from those of psychosis or substance abuse. The GNDS did not statistically differentiate head injury effects but in these populations did detect neurological impairment, which supports the utility of this index as an indicator of overall neurological impairment.

Effects of alcohol consumption on lateralized aggression in Anolis carolinensis

Previous work has suggested that the lizard Anolis carolinensis, like many other reptiles, has a functionally split brain. Specifically, the left eye of this species projects primarily to the right hemisphere (and vice versa), there is no corpus callosum, and the physical placement of the eyes restricts their field(s) of vision to one region of hemispace. The current experiment used this preparation to examine the effect of alcohol administration and withdrawal on lateralized brain functioning during territorial aggression. Thirteen adult males were divided into control (CON) or alcohol (ETOH) groups. Baseline territorial aggression was assessed, following which ETOH subjects were then given twice daily solutions of 19% alcohol. After 19 days of ETOH consumption, territorial aggression was again assessed. Eye use during aggressive encounters was measured either following short periods (24 h) of alcohol withdrawal, or 90 m following alcohol consumption. Control subjects were found to have a predominance of left eye/right hemisphere-mediated aggressive responses, as has previously been reported. Alcohol withdrawn subjects were found to have a suppression of left eye/right hemisphere-mediated aggression. This reached statistical significance on several measures of aggression, including the number of dewlaps and headbob (P < 0.001) and the total number of aggressive responses (P = 0.001). Consumption of ETOH reversed this pattern and reinstated the normal pattern of left eye/right hemisphere dominance during aggression. Conversely, right eye/left hemisphere mediation of aggression was found to be increased, or not affected, during alcohol withdrawal, and to show no differences from CON following ETOH administration. Extrapolating from other recent findings in this species, these results suggest that the stress caused by ETOH withdrawal on the CNS may differentially effect the right hemisphere of the brain while having little effect on the left.

Intermanual differences on motor and psychomotor tests in alcoholics: no evidence for selective right-hemisphere dysfunction

Some previous studies have suggested that alcoholics exhibit selective right-hemisphere dysfunction, based on alcoholics' poor performance on tests believed to subserve the right hemisphere. However, some of these experiments did not account adequately for differences in difficulty or novelty in putative right hemisphere tasks. This experiment was designed to evaluate and compare intermanual differences in grip strength, motor speed, fine-motor dexterity, and nonverbal problem-solving ability in 93 recently detoxified alcoholics, 54 long-term abstinent alcoholics, and 73 nonalcoholic controls. All subjects were right-handed men, matched for age and education, and both alcoholic groups had similar drinking histories. Using percent difference scores to assess intermanual differences, adjusted for demographics where appropriate, we found that, although recently detoxified alcoholics demonstrate some motor and psychomotor impairments, there is no evidence using these tests to suggest the right hemisphere is selectively more vulnerable to the effects of chronic alcohol abuse.

A neuropsychologic profile of adolescent alcoholics

Male and female adolescents who qualified for a DSM-III-R diagnosis of Alcohol Abuse or Dependence and a control sample of nonalcohol-abusing male and female adolescents were administered a battery of intellectual, achievement, and neuropsychologic tests. Alcohol-abusing adolescents were found to have significantly lower verbal and full-scale IQ scores than controls. Furthermore, alcohol-abusing adolescents were found to have a trend toward lower age-standardized scores on achievement tests of reading ability and spelling. Surprisingly, alcohol-abusing adolescents made less perseverative errors and commission errors on a learning and memory task than controls. Control males performed worse on the Wisconsin Card Sort than alcoholic males, whereas alcohol-abusing females performed worse than control females. In addition, alcoholic subjects scored better than controls on a measure of visual memory sensitivity. The results indicate that adolescent alcohol abusers in general have poorer language skills than adolescents who do not abuse alcohol. However, in contrast to results obtained from studies of adult alcoholics, there is little evidence of significant brain damage as revealed by using neuropsychologic test performance.

Postural sway in children from pedigrees exhibiting a high density of alcoholism

A total of 98 children participated in a study of the neurobehavioral characteristics of individuals from pedigrees in which there was a high density of alcoholism. Two groups of children were evaluated (High and Low Risk) using a sensitive movement platform and a variety of methods to challenge the motor system. High-Risk children showed a greater decrement in postural steadiness when visual input was removed than did Low-Risk children. Additionally, the monopedal stances revealed hemispheric differences in postural sway as a function of risk status. The amount of sway exhibited was correlated with the latency of P300 recorded using a visual task. Both appear to be indicators of neuropathological changes. The present results suggest that postural sway may be a neurobehavioral marker for alcoholism risk.