Thinning of the corpus callosum in older alcoholic men: a magnetic resonance imaging study

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.

Ethanol-induced changes in the expression of proteins related to neurotransmission and metabolism in different regions of the rat brain

Despite extensive description of the damaging effects of chronic alcohol exposure on brain structure, mechanistic explanations for the observed changes are just emerging. To investigate regional brain changes in protein expression levels following chronic ethanol treatment, one rat per sibling pair of male Wistar rats was exposed to intermittent (14 h/day) vaporized ethanol, the other to air for 26 weeks. At the end of 24 weeks of vapor exposure, the ethanol group had blood ethanol levels averaging 450 mg%, had not experienced a protracted (> 16 h) withdrawal from ethanol, and revealed only mild evidence of hepatic steatosis. Extracted brains were micro-dissected to isolate the prefrontal cortex (PFC), dorsal striatum (STR), corpus callosum genu (CCg), CC body (CCb), anterior vermis (AV), and anterior dorsal lateral cerebellum (ADLC) for protein analysis with two-dimensional gel electrophoresis. Expression levels for 54 protein spots were significantly different between the ethanol- and air-treated groups. Of these 54 proteins, tandem mass spectroscopy successfully identified 39 unique proteins, the levels of which were modified by ethanol treatment: 13 in the PFC, 7 in the STR, 2 in the CCg, 7 in the CCb, 7 in the AV, and 5 in the ADLC. The functions of the proteins altered by chronic ethanol exposure were predominantly associated with neurotransmitter systems in the PFC and cell metabolism in the STR. Stress response proteins were elevated only in the PFC, AV, and ADLC perhaps supporting a role for frontocerebellar circuitry disruption in alcoholism. Of the remaining proteins, some had functions associated with cytoskeletal physiology (e.g., in the CCb) and others with transcription/translation (e.g., in the ADLC). Considered collectively, all but 4 of the 39 proteins identified in the present study have been previously identified in ethanol gene- and/or protein-expression studies lending support for their role in ethanol-related brain alterations.

Subcortical volumes in long-term abstinent alcoholics: associations with psychiatric comorbidity

BACKGROUND

Research in chronic alcoholics on memory, decision-making, learning, stress, and reward circuitry has increasingly highlighted the importance of subcortical brain structures. In addition, epidemiological studies have established the pervasiveness of co-occurring psychiatric diagnoses in alcoholism. Subcortical structures have been implicated in externalizing pathology, including alcohol dependence, and in dysregulated stress and reward circuitry in anxiety and mood disorders and alcohol dependence. Most studies have focused on active or recently detoxified alcoholics, while subcortical structures in long-term abstinent alcoholics (LTAA) have remained relatively uninvestigated.

METHODS

Structural MRI was used to compare volumes of 8 subcortical structures (lateral ventricles, thalamus, caudate, putamen, pallidum, hippocampus, amygdala, and nucleus accumbens) in 24 female and 28 male LTAA (mean abstinence=6.3 years, mean age= 46.6 years) and 23 female and 25 male nonalcoholic controls (NAC) (mean age=45.6 years) to explore relations between subcortical brain volumes and alcohol use measures in LTAA and relations between subcortical volumes and psychiatric diagnoses and symptom counts in LTAA and NAC.

RESULTS

We found minimal differences between LTAA and NAC in subcortical volumes. However, in LTAA, but not NAC, volumes of targeted subcortical structures were smaller in individuals with versus without comorbid lifetime or current psychiatric diagnoses, independent of lifetime alcohol consumption.

CONCLUSIONS

Our finding of minimal differences in subcortical volumes between LTAA and NAC is consistent with LTAA never having had volume deficits in these regions. However, given that imaging studies have frequently reported smaller subcortical volumes in active and recently detoxified alcoholics compared to controls, our results are also consistent with the recovery of subcortical volumes with sustained abstinence. The finding of persistent smaller subcortical volumes in LTAA, but not NAC, with comorbid psychiatric diagnoses, suggests that the smaller volumes are a result of the combined effects of chronic alcohol dependence and psychiatric morbidity and suggests that a comorbid psychiatric disorder (even if not current) interferes with the recovery of subcortical volumes.

Callosal microstructural abnormalities in Alzheimer's disease and alcoholism: same phenotype, different mechanisms

Magnetic resonance (MRI) and diffusion tensor imaging (DTI) data were acquired in 13 Alzheimer's disease (AD) patients, 15 elderly alcoholics, and 32 elderly controls. Midsagittal area, length, dorsoventral height, fractional anisotropy (FA), and mean diffusivity (MD) of the total corpus callosum and volume of the lateral ventricles were measured; area, FA, and MD were also determined for the callosal genu, body, and splenium. On DTI, both patient groups had lower FA and higher MD than controls in all callosal regions. On MRI, both patient groups had smaller genu than controls; additional size deficits were present in the alcoholism group's callosal body and the AD group's splenium. The callosal arch was higher in the AD but not the alcoholic group compared with controls. The two patient groups had larger ventricles than controls, and the AD group had larger ventricles than the alcoholic group. Callosal area correlated with its height, and callosal FA and MD correlated with ventricular volume in AD, whereas callosal area correlated only with FA in alcoholics. In AD, the disruption of the callosal integrity, which was associated with distorted callosal shape, was related to ventricular dilation, which has been shown in twin studies to be under a multitude of genetic, polygenetic, and environmental influences. Conversely, in alcoholism, disruption of callosal microstructural integrity was related to shrinkage of the corpus callosum itself.

Comorbidity of ADHD and Substance Use Disorder (SUD): a neuroimaging perspective

INTRODUCTION

ADHD has a high comorbidity with substance use disorders (SUD). Both diseases have profound social, psychological, and economic consequences and are therefore highly relevant for health systems. The high comorbidity indicates some shared underlying neurobiological substrates. Knowing these substrates may increase the understanding of the disease and help identify therapeutic processes.

METHOD

Neuroimaging studies of ADHD were reviewed and similarities with SUD identified. For this a PubMed research was conducted with the search terms ADHD, SUD, MRI or positron emission tomography (PET) or spectroscopy or imaging.

RESULTS

Similarities were found, in both PET and fMRI studies, between patients with ADHD and those with addiction-related craving. Results from structural MRI and MR spectroscopy do not support a common pathophysiological background, probably because of the lack of studies on craving.

DISCUSSION

ADHD and SUD-related craving share some neurobiological similarities. One reason may be that patients with addiction show more craving when they also suffer from ADHD. The present review thus supports the conclusion from an earlier meta-analysis of clinical studies which found that adequate treatment of ADHD reduces craving and relapse into substance use.

Transcallosal white matter degradation detected with quantitative fiber tracking in alcoholic men and women: selective relations to dissociable functions

INTRODUCTION

Excessive alcohol consumption can adversely affect white matter fibers and disrupt transmission of neuronal signals. Here, we examined six anatomically defined transcallosal white matter fiber bundles and asked whether any bundle was specifically vulnerable to alcohol, what aspect of white matter integrity was most affected, whether women were more vulnerable than men, and whether evidence of compromise in specific bundles was associated with deficits in balance, sustained attention, associative learning, and psychomotor function, commonly affected in alcoholics.

METHODS

Diffusion tensor imaging quantitative fiber tracking assessed integrity of six transcallosal white matter bundles in 87 alcoholics (59 men, 28 women) and 88 healthy controls (42 men, 46 women). Measures included orientational diffusion coherence (fractional anisotropy, FA) and magnitude of diffusion, quantified separately for axial (longitudinal; lambdaL) and radial (transverse; lambdaT) diffusivity. The Digit Symbol Test and a test of ataxia were also administered.

RESULTS

Alcoholism negatively affected callosal FA and lambdaT of all but the sensory-motor bundle. Women showed no evidence for greater vulnerability to alcohol than men. Multiple regression analyses confirmed a double dissociation: higher diffusivity in sensory-motor and parietal bundles was associated with poorer balance but not psychomotor speed, whereas higher diffusivity in prefrontal and temporal bundles was associated with slower psychomotor speed but not balance.

CONCLUSIONS

This study revealed stronger alcohol effects for FA and radial diffusivity than axial diffusivity, suggesting myelin degradation, but no evidence for greater vulnerability to alcohol in women than men. The presence of brain-behavior relationships provides support for the role of alcoholism-related commissural white matter degradation as a substrate of cognitive and motor impairment. Identification of a double dissociation provides further support for the role of selective white matter integrity in specific domains of performance.

MR diffusion tensor imaging: a window into white matter integrity of the working brain

As Norman Geschwind asserted in 1965, syndromes resulting from white matter lesions could produce deficits in higher-order functions and "disconnexion" or the interruption of connection between gray matter regions could be as disruptive as trauma to those regions per se. The advent of in vivo diffusion tensor imaging, which allows quantitative characterization of white matter fiber integrity in health and disease, has served to strengthen Geschwind's proposal. Here we present an overview of the principles of diffusion tensor imaging (DTI) and its contribution to progress in our current understanding of normal and pathological brain function.

Alcohol Pathophysiology

There is no specialized alcohol addiction area in the brain; rather, alcohol acts on a wide range of excitatory and inhibitory nervous networks to modulate neurotransmitters actions by binding with and altering the function of specific proteins. With no hemato-encephalic barrier for alcohol, its actions are strongly related to the amount of intake. Heavy alcohol intake is associated with both structural and functional changes in the central nervous system with long-term neuronal adaptive changes contributing to the phenomena of tolerance and withdrawal. The effects of alcohol on the function of neuronal networks are heterogeneous. Because ethanol affects neural activity in some brain sites but is without effect in others, its actions are analyzed in terms of integrated connectivities in the functional circuitry of neuronal networks, which are of particular interest because of the cognitive interactions discussed in the manuscripts contributing to this review. Recent molecular data are reviewed as a support for the other contributions dealing with cognitive disturbances related to alcohol acute and addicted consumption.

The effect of moderate to heavy alcohol consumption on neuropsychological performance as measured by the repeatable battery for the assessment of neuropsychological status

BACKGROUND

Excessive alcohol use is associated with damage to the structure and function of the brain and impairment of cognition and behavior. Traditional test batteries used to assess cognitive performance in alcoholics are extensive and costly, limiting their use across various clinical and research settings. The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) is a relatively new instrument that attempts to overcome some of these limitations. As yet the individual effect of moderate to heavy alcohol consumption on RBANS performance has not been examined. The primary aim of this study was to explore and quantify differences in performance between controls and drinkers on the RBANS and to examine the influence of age, gender, and alcohol use patterns on test performance.

METHODS

Data from a subset of "Using Our Brains" (UoB) donors (n = 28) still actively drinking and meeting criteria for moderate to heavy alcohol use (30 to 80 g of ethanol per day) (Harper, 1988) and 28 matched controls (age, education, and premorbid Intelligence Quotient) were compared.

RESULTS

Participants in the alcohol group performed below the healthy control group on the visuospatial and immediate memory index, and also on the RBANS total score p < 0.001 and showed a greater decline in RBANS scores from estimated cross-sectional premorbid levels. There was a positive association between alcohol ingestion in the preceding 12 months and the language index p < 0.03 and the semantic fluency subtest (p < 0.03). Age was negatively associated with story memory (p < 0.02), coding (p < 0.001), list recognition (p < 0.01), story recall (p < 0.03), and figure recall (p < 0.02).

CONCLUSION

Our results suggest that the RBANS is able to detect and characterize differences in verbal fluency, visuospatial skills, components of declarative memory, and psychomotor speed between healthy controls and moderate to heavy active alcohol users. Executive functions, commonly affected by alcoholism and not included in the RBANS, require assessment with additional measures.

Neurocognitive correlates of white matter quality in adolescent substance users

BACKGROUND

Progressive myelination during adolescence implicates an increased vulnerability to neurotoxic substances and enduring neurocognitive consequences. This study examined the cognitive manifestations of altered white matter microstructure in chronic marijuana and alcohol-using (MJ+ALC) adolescents.

METHODS

Thirty-six MJ+ALC adolescents (ages 16-19) and 36 demographically similar controls were evaluated with diffusion tensor imaging (Bava et al., 2009) and neurocognitive tests. Regions of group difference in fractional anisotropy (FA) and mean diffusivity (MD) were analyzed in relation to cognitive performance.

RESULTS

In users, lower FA in temporal areas related to poorer performance on attention, working memory, and speeded processing tasks. Among regions where users had higher FA than controls, occipital FA was positively associated with working memory and complex visuomotor sequencing, whereas FA in anterior regions was negatively associated with verbal memory performance.

CONCLUSIONS

Findings suggest differential influences of white matter development on cognition in MJ+ALC using adolescents than in non-using peers. Neuroadaptation may reflect additive and subtractive responses to substance use that are complicated by competing maturational processes.

The impact of chronic cigarette smoking on recovery from cortical gray matter perfusion deficits in alcohol dependence: longitudinal arterial spin labeling MRI

BACKGROUND

Neuroimaging studies reported cerebral perfusion abnormalities in individuals with alcohol use disorders. However, no longitudinal magnetic resonance imaging (MRI) studies of cerebral perfusion changes during abstinence from alcohol have been reported.

METHODS

Arterial spin labeling MRI was used to evaluate cortical gray matter perfusion changes in short-term abstinent alcohol dependent individuals in treatment and to assess the impact of chronic cigarette smoking on perfusion changes during abstinence. Seventy-six patients were scanned at least once. Data from 19 non-smoking (17 males, 2 females) and 22 smoking (21 males, 1 female) patients scanned at 1 and 5 weeks of abstinence were used to assess perfusion changes over time. Twenty-eight age-equated healthy controls (25 males, 3 females) were scanned for cross-sectional comparison, 13 of them were scanned twice. Given the age range of the cohort (28 to 68 years), age was used as a covariate in the analyses. Mean perfusion was measured in voxels of at least 80% gray matter in the frontal and parietal lobes and related to neurocognitive and substance use measures.

RESULTS

At 1 week of abstinence, frontal and parietal gray matter perfusion in smoking alcoholics was not significantly different from that in non-smoking alcoholics, but each group's perfusion values were significantly lower than in controls. After 5 weeks of abstinence, perfusion of frontal and parietal gray matter in non-smoking alcoholics was significantly higher than that at baseline. However, in smoking alcoholics, perfusion was not significantly different between the time-points in either region. The total number of cigarettes smoked per day was negatively correlated with frontal gray matter perfusion measured at 5 weeks of abstinence. Lobar perfusion measures did not correlate significantly with drinking severity or cognitive domain measures at either time-point.

CONCLUSION

Although cerebral perfusion in alcohol dependent individuals shows improvement with abstinence from alcohol, cigarette smoking appears to hinder perfusion improvement.

Altered white matter integrity in adolescent binge drinkers

BACKGROUND

White matter integrity has been found to be compromised in adult alcoholics, but it is unclear when in the course of alcohol exposure white matter abnormalities become apparent. This study assessed microstructural white matter integrity among adolescent binge drinkers with no history of an alcohol use disorder.

METHODS

We used diffusion tensor imaging to examine fractional anisotropy (FA), a measure of directional coherence of white matter tracts, among teens with (n = 14) and without (n = 14) histories of binge drinking but no history of alcohol use disorder, matched on age, gender, and education.

RESULTS

Binge drinkers had lower FA than controls in 18 white matter areas (clusters > or =27 contiguous voxels, each with p < 0.01) throughout the brain, including the corpus callosum, superior longitudinal fasciculus, corona radiata, internal and external capsules, and commissural, limbic, brainstem, and cortical projection fibers, while exhibiting no areas of higher FA. Among binge drinkers, lower FA in 6 of these regions was linked to significantly greater lifetime hangover symptoms and/or higher estimated peak blood alcohol concentrations.

CONCLUSIONS

Binge drinking adolescents demonstrated widespread reductions of FA in major white matter pathways. Although preliminary, these results could indicate that infrequent exposure to large doses of alcohol during youth may compromise white matter fiber coherence.

The neuropathology of alcohol-related brain damage

Excessive alcohol use can cause structural and functional abnormalities of the brain and this has significant health, social and economic implications for most countries in the world. Even heavy social drinkers who have no specific neurological or hepatic problems show signs of regional brain damage and cognitive dysfunction. Changes are more severe and other brain regions are damaged in patients who have additional vitamin B1 (thiamine) deficiency (Wernicke-Korsakoff syndrome). Quantitative studies and improvements in neuroimaging have contributed significantly to the documentation of these changes but mechanisms underlying the damage are not understood. A human brain bank targeting alcohol cases has been established in Sydney, Australia, and tissues can be used for structural and molecular studies and to test hypotheses developed from animal models and in vivo studies. The recognition of potentially reversible changes and preventative medical approaches are important public health issues.

Frontal white matter and cingulum diffusion tensor imaging deficits in alcoholism

BACKGROUND

Alcoholism-related deficits in cognition and emotion point toward frontal and limbic dysfunction, particularly in the right hemisphere. Prefrontal and anterior cingulate cortices are involved in cognitive and emotional functions and play critical roles in the oversight of the limbic reward system. In the present study, we examined the integrity of white matter tracts that are critical to frontal and limbic connectivity.

METHODS

Diffusion tensor magnetic resonance imaging (DT-MRI) was used to assess functional anisotropy (FA), a measure of white matter integrity, in 15 abstinent long-term chronic alcoholic and 15 demographically equivalent control men. Voxel-based and region-based analyses of group FA differences were applied to these scans.

RESULTS

Alcoholic subjects had diminished frontal lobe FA in the right superior longitudinal fascicles II and III, orbitofrontal cortex white matter, and cingulum bundle, but not in corresponding left hemisphere regions. These right frontal and cingulum white matter regional FA measures provided 97% correct group discrimination. Working Memory scores positively correlated with superior longitudinal fascicle III FA measures in control subjects only.

CONCLUSIONS

The findings demonstrate white matter microstructure deficits in abstinent alcoholic men in several right hemisphere tracts connecting prefrontal and limbic systems. These white matter deficits may contribute to underlying dysfunction in memory, emotion, and reward response in alcoholism.

Frontal Callosal Fiber Integrity Selectively Predicts Coordinated Psychomotor Performance in Chronic Alcoholism

INTRODUCTION: Quantitative fiber tracking with diffusion tensor imaging (DTI) provides a new approach for assessing deficits in the microstructural integrity of white matter circuits that may underlie cognitive deficits associated with conditions affecting white matter, including chronic alcoholism. METHODS: Alcoholic men and women (n=87) and healthy controls (n=88) performed the Digit Symbol (DS) test and underwent structural and diffusion tensor imaging. Measures of fractional anisotropy (FA) of fibers passing through genu and splenium were computed, as were size of genu and splenium fiber target regions of interest (ROI). RESULTS: Alcoholics scored lower than controls on the DS and had even greater deficits in genu than splenium fiber FA. In alcoholics, fiber FA of the genu selectively predicted DS scores after accounting for splenium FA. Neither fiber FA measure predicted incidental recall of the symbols used in the task. Size of genu and splenium ROI, although reduced in alcoholics, did not predict DS score or incidental recall. CONCLUSIONS: Quantitative tractography of frontal fibers connecting left and right hemispheres selectively predicted performance by alcoholics on a coordinated psychomotor task and provide support for frontally based systems in Digit Symbol performance, both of which are compromised in recovering alcoholics.

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.

Interaction of thiamine deficiency and voluntary alcohol consumption disrupts rat corpus callosum ultrastructure

The relative roles of alcohol and thiamine deficiency in causing brain damage remain controversial in alcoholics without the Wernicke-Korsakoff syndrome. Experimental control over alcohol consumption and diet are impossible in humans but can be accomplished in animal models. This experiment was designed to differentiate the separate and combined effects on the macro- and ultrastructure of the corpus callosum of thiamine deficiency and voluntary alcohol consumption. Adult male alcohol-preferring (P) rats (9 chronically alcohol-exposed and 9 water controls) received a thiamine-deficient diet for 2 weeks. There were four groups: five rats previously exposed to alcohol were treated with pyrithiamine (a thiamine phosphorylation inhibitor); five rats never exposed to alcohol were treated with pyrithiamine; four alcohol-exposed rats were treated with thiamine; and four rats never exposed to alcohol were treated with thiamine. On day 14, thiamine was restored in all 18 rats; 2 weeks later the 10 pyrithiamine-treated rats received intraperitoneal thiamine. The rats were perfused 61 days post-pyrithiamine treatment at age 598 days. Brains were dissected and weight and volumes were calculated. Sagittal sections were stained to measure white matter structures. The corpus callosum was examined using transmission electron microscopy to determine density of myelinated fibers, fiber diameter, and myelin thickness. The corpus callosum in the alcohol/pyrithiamine group was significantly thinner, had greater fiber density, higher percentage of small fibers, and myelin thinning than in the alcohol/thiamine and water/thiamine groups. Several measures showed a graded effect, where the alcohol/pyrithiamine group had greater pathology than the water/pyrithiamine group, which had greater pathology than the two thiamine-replete groups. Across all 16 rats, thinner myelin sheaths correlated with higher percentage of small fibers. Myelin thickness and axon diameter together accounted for 71% of the variance associated with percentage of small fibers. Significant abnormalities in the alcohol/pyrithiamine group and lack of abnormality in the alcohol-exposed/thiamine-replete group indicate that thiamine deficiency caused white matter damage. The graded abnormalities across the dually to singly treated animals support a compounding effect of alcohol exposure and thiamine depletion, and indicate the potential for interaction between alcohol and thiamine deficiency in human alcohol-related brain damage.

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.

Alcoholism and judgments of affective stimuli

This study sought to differentiate alcoholism-related changes in judgments of emotional stimuli from those of other populations in which such changes have been documented. Two sets of visual stimuli, one containing words and the other containing drawings of faces (representing a range of emotional content), were presented to abstinent alcoholic adults with and without Korsakoff's syndrome, as well as to a healthy control group and four groups of patients with other neurobehavioral disorders: Parkinson's disease, schizophrenia, depression, and posttraumatic stress disorder. Participants rated the stimuli according to emotional valence and intensity of emotion. Results implicated bi-hemispheric frontal and subcortical involvement in the abnormalities of emotion identification associated with alcoholism, and they also support the notion of age-related vulnerabilities in conjunction with alcoholism.

Deformation-based morphometry of brain changes in alcohol dependence and abstinence

Brain atrophy associated with chronic alcohol consumption is partially reversible after cessation of drinking. Recovering alcoholics (RA, 45+/-8 years) were studied with MRI within 1 week of entering treatment, with follow-up at 8 months. Light drinkers (LD) were studied with MRI twice 1 year apart. For each participant, deformation maps of baseline structure and longitudinal size changes between baseline and follow-up scans were created using nonlinear registration techniques. ANCOVA assessed group differences and regression methods examined relationships between deformation maps and measures of drinking severity or baseline atrophy. At baseline, RA showed significant atrophy in the frontal and temporal lobes. Longitudinally, abstainers recovered tissue volumes significantly faster than LD in parietal and frontal lobes. When comparing abstainers to relapsers, additional regions with significantly greater recovery in abstainers were temporal lobes, thalamus, brainstem, cerebellum, corpus callosum, anterior cingulate, insula, and subcortical white matter. Gray matter volume at baseline predicted volume recovery during abstinence better than white matter. Drinking severity was not significantly related to brain structural changes assessed with this method. Longitudinally, deformation-based morphometry confirmed tissue recovery in RAs who maintain long-term sobriety. Abstinence-associated tissue volume gains are significant in focal parts of the fronto-ponto-cerebellar circuit that is adversely affected by heavy drinking.

Brain morphometry and cognitive performance in detoxified alcohol-dependents with preserved psychosocial functioning

The extent of structural brain damage and related cognitive deficits has been little described in alcohol-dependent individuals with preserved social functioning. Thus, we investigated the relationship between regional alterations, executive performance, and drinking history. Volumes of gray and white matter were assessed using magnetic resonance imaging voxel-based morphometry in healthy men and in detoxified alcohol-dependent men with good psychosocial functioning. Their executive performance was assessed using neuropsychological tests. Regression analyses were carried out in the regions in which volume differences were detected. Decreases in gray matter were detected bilaterally in alcohol-dependents in the dorsolateral frontal cortex (up to 20% lower), and to a lesser extent in the temporal cortex, insula, thalamus, and cerebellum. Decreases in white matter volume were widespread, being up to 10% in corpus callosum. The degradation of neuropsychological performance correlated with gray matter volume decreases in the frontal lobe, insula, hippocampus, thalami and cerebellum, and with white matter decrease in the brainstem. An early age at first drinking was associated with decreased gray matter volumes in the cerebellum, brainstem (pons), and frontal regions. Regional alteration in gray and white matter volume was associated with impairment of executive function despite preserved social and somatic functioning in detoxified patients. Besides involving frontal regions, these findings are consistent with a cerebello-thalamo-cortical model of impaired executive functions in alcohol-dependent individuals.

Effects of alcohol and combined marijuana and alcohol use during adolescence on hippocampal volume and asymmetry

BACKGROUND

Converging lines of evidence suggest that the hippocampus may be particularly vulnerable to deleterious effects of alcohol and marijuana use, especially during adolescence. The goal of this study was to examine hippocampal volume and asymmetry in adolescent users of alcohol and marijuana.

METHODS

Participants were adolescent (aged 15-18) alcohol (ALC) users (n=16), marijuana and alcohol (MJ+ALC) users (n=26), and demographically similar controls (n=21). Extensive exclusionary criteria included prenatal toxic exposure, left handedness, and psychiatric and neurologic disorders. Substance use, cognitive, and anatomical measures were collected after at least 2 days of abstinence from all substances.

RESULTS

Adolescent ALC users demonstrated a significantly different pattern of hippocampal asymmetry (p<.05) and reduced left hippocampal volume (p<.05) compared to MJ+ALC users and non-using controls. Increased alcohol abuse/dependence severity was associated with increased right>left (R>L) asymmetry and smaller left hippocampal volumes while marijuana abuse/dependence was associated with increased L>R asymmetry and larger left hippocampal volumes. Although MJ+ALC users did not differ from controls in asymmetry, functional relationships with verbal learning were found only among controls, among whom greater right than left hippocampal volume was associated with superior performance (p<.05).

CONCLUSIONS

Aberrations in hippocampal asymmetry and left hippocampal volumes were found for adolescent heavy drinkers. Further, the functional relationship between hippocampal asymmetry and verbal learning was abnormal among adolescent substance users compared to healthy controls. These findings suggest differential effects of alcohol and combined marijuana and alcohol use on hippocampal morphometry and the relationship between hippocampal asymmetry and verbal learning performance among adolescents.

Developmental changes in visual line bisection in women throughout adulthood

It has been suggested that some hemispheric asymmetries change in a systematic way from young adulthood to older age. However, little is known whether these changes are due to differential aging of a single hemisphere or based on age-related alterations of interhemispheric interactions. A sample of 281 right-handed neurologically healthy participants (151 women), ranging from age 20 to 79, was investigated with a line-bisection task. Previous studies indicate the midpoint estimation shows a consistent leftward bias from the veridical center, which is accentuated when the left hand is used to bisect lines. These findings support the view of a right hemispheric superiority in spatial attention. This study revealed this pattern to be stable in men throughout adulthood. However, women from 50 to 69 years of age showed a reduced leftward bias and a reduced hand effect compared to men and younger women. The results suggest that developmental changes in hemispheric asymmetry of spatial attention are more pronounced in women and support the view that neuromorphological changes during adulthood differ between sexes.

Longitudinal brain magnetic resonance imaging study of the alcohol-preferring rat. Part II: effects of voluntary chronic alcohol consumption

BACKGROUND

Tracking the dynamic course of human alcoholism brain pathology can be accomplished only through naturalistic study and without opportunity for experimental manipulation. Development of an animal model of alcohol-induced brain damage, in which animals consume large amounts of alcohol following cycles of alcohol access and deprivation and are examined regularly with neuroimaging methods, would enable hypothesis testing focused on the degree, nature, and factors resulting in alcohol-induced brain damage and the prospects for recovery or relapse.

METHODS

We report the results of longitudinal magnetic resonance imaging (MRI) studies of the effects of free-choice chronic alcohol intake on the brains of 2 cohorts of selectively bred alcohol-preferring (P) rats. In the companion paper, we described the MRI acquisition and analysis methods, delineation of brain regions, and growth patterns in total brain and selective structures of the control rats in the present study. Both cohorts were studied as adults for about 1 year and consumed high doses of alcohol for most of the study duration. The paradigm involved a 3-bottle choice with 0, 15 (or 20%), and 30% (or 40%) alcohol available in several different exposure schemes: continuous exposure, cycles of 2 weeks on followed by 2 weeks off alcohol, and binge drinking in the dark.

RESULTS

Brain structures of the adult P rats in both the alcohol-exposed and the water control conditions showed significant growth, which was attenuated in a few measures in the alcohol-exposed groups. The region with the greatest demonstrable effect was the corpus callosum, measured on midsagittal images.

CONCLUSION

The P rats showed an age-alcohol interaction different from humans, in that normal growth in selective brain regions that continues in adult rats was retarded.

Longitudinal Brain Magnetic Resonance Imaging Study of the Alcohol-Preferring Rat. Part I: Adult Brain Growth

BACKGROUND

The alcohol-preferring (P) rat, a Wistar strain selectively bred to consume large amounts of alcohol voluntarily, has been used as an animal model of human alcoholism for 3 decades. Heretofore, knowledge about brain morphology has been confined to postmortem examination. Quantitative neuroimaging procedures make it feasible to examine the potential longitudinal effects of alcohol exposure in vivo, while controlling modifying factors, such as age, nutrition, and exercise. To date, few imaging studies have considered what morphological changes occur with age in the rodent brain, and none has systematically applied quantitative neuroimaging approaches to measure volume changes in regional brain structures over extended periods in the adult rat.

METHODS

We used structural magnetic resonance imaging (MRI) in a longitudinal design to examine 2 cohorts of adult P rats, never exposed to alcohol: Cohort A included 8 rats, 7 of which survived the entire study (578 days) and 4 MRI sessions; Cohort B included 9 rats, all of which survived the study (452 days) and 5 MRI sessions.

RESULTS

Growth in whole-brain volume reached maximal levels by about 450 days of age, whereas body weight continued its gain without asymptote. Growth was not uniform across the brain structures measured. Over the initial 12 months of the study, the corpus callosum area expanded 36%, cerebellum 17%, and hippocampus 10%, whereas ventricle size was unchanged. Factors affecting growth rate estimates included litter effects, MR image signal-to-noise ratio, and measurement error.

CONCLUSION

Unlike longitudinal human reports of regional volume declines in aging brain tissue, several brain structures in adult rats continued growing, and some growth patterns were litter-dependent. Determining normal regional growth patterns of brain and of the substantial variance exerted by litter differences, even in selectively bred rats, is essential for establishing baselines against which normal and aberrant dynamic changes can be detected in animal models of aging and disease.

Age-related degeneration of corpus callosum measured with diffusion tensor imaging

The corpus callosum is the major commissure connecting the cerebral hemispheres, and there is evidence of its change with aging. The sub-regions of the corpus callosum (genu, rostral body, anterior midbody, posterior midbody, isthmus, splenium) respectively comprise fibers connecting heteromodal- and unimodal-associated cortical regions, and it is known that abnormalities of the corpus callosum are correlated with abnormalities in cognition and behavior. Yet, little is known about changes in the tissue characteristics of its sub-regions. We assessed age-related changes in fractional anisotropy and mean diffusivity in the sub-regions of the corpus callosum using diffusion tensor imaging. We studied 42 healthy right-handed individuals aged 21-73 years. There were no significant interactions of sex x region. Age has significant negative correlation with fractional anisotropy in the genu (P < 0.001), rostral body (P < 0.001), and isthmus (P = 0.005). Fractional anisotropy of the anterior midbody was correlated negatively with age at a trend level (P = 0.022). Age was significantly positively correlated with mean diffusivity in the genu (P = 0.001), rostral body (P = 0.002), anterior midbody (P = 0.001), and isthmus (P = 0.001). Age-related changes were detected in the sub-regions where their projection areas are thought to be vulnerable to normal aging. This suggested that fractional anisotropy and mean diffusivity values of the corpus callosum sub-regions could serve as markers of disturbance across the respective projection areas.

Dysmorphology and microstructural degradation of the corpus callosum: Interaction of age and alcoholism

Chronic alcohol abuse is a ubiquitous health and societal problem, with a growing prevalence in the older population. Alcoholism is a source of substantial deterioration in brain tissue and has been consistently observed in vivo and postmortem in white matter. To quantify the potential compounded effect of age and alcoholism, we used conventional structural MRI and diffusion tensor imaging (DTI) to examine the macrostructural and microstructural integrity of the corpus callosum, one of the most prominent white matter structures of the brain, in 131 adults, age 27-75 years. Compared with the 74 controls, the 40 alcoholic men and 17 alcoholic women, who were abstinent from alcohol for an average of 3 months, showed similar patterns and extents of callosal shrinkage, which was greatest in the genu and body and less prominent in the splenium. Microstructural integrity was measured with DTI as fractional anisotropy, an index of intravoxel orientational coherence of white matter fibers, and bulk mean diffusivity, an index of the amount of intravoxel water motility. The macrostructural shrinkage was accompanied by abnormalities in anisotropy and diffusivity of the microstructural environment of these callosal regions, indicative of disruption of structural constituents of local brain white matter. Correlational analyses revealed an age-alcohol interaction, where older alcoholics had smaller genu and splenium and higher diffusivity in these regions than younger alcoholics. Significant correlations between regional MRI and DTI measures and performance on working memory, visuospatial ability, and gait and balance provided evidence for the functional ramifications of the callosal abnormalities in the alcoholics. Thus, despite abstinence from alcohol, the interaction of age and recent alcoholism history exerted a compounded untoward effect on callosal macrostructure and microstructure.

Corpus Callosum Volume in Railroad Workers With Chronic Exposure to Solvents

OBJECTIVE

Changes to cognition and behavior have been reported after long-term exposure to solvents. Solvents are hypothesized to affect brain white matter. To test this, we examined the volume of the corpus callosum in workers with a history of exposure to solvents.

METHODS

We manually traced (blind to group membership) the volume of the corpus callosum in 31 railroad workers and 31 matched controls.

RESULTS

There was a decrease in the genu of the corpus callosum in the solvent-exposed workers compared with controls. A smaller volume of the genu of the corpus callosum was associated with greater exposure and worse performance on cognitive tasks.

CONCLUSIONS

This study supports the hypothesis that occupational exposure to solvents affects the anterior white matter of the brain and is related to extent of exposure and degree of cognitive change.

Deformation-based brain morphometry to track the course of alcoholism: differences between intra-subject and inter-subject analysis

Substantial changes in brain morphology mark the course of alcoholism from development through dependence, recovery, and relapse. These changes can be characterized with deformation-based morphometry, which quantifies shape differences between anatomical structures, either in different subjects (cross-sectional) or in the same subject over time (longitudinal). Here we present analyses of data from a longitudinal magnetic resonance imaging (MRI) study on the effects of alcoholism on brain structure. Images were acquired from alcoholic women (n=7, mean age 47.8+/-8.3 years) and age-matched control women (n=16, mean age 51.2+/-7.5 years). From each subject, we acquired two structural MR brain images, separated by approximately 2 years (mean 21.6+/-7 months). We performed two types of morphometry using log-Jacobian maps of inter-subject and intra-subject nonrigid coordinate transformations, justified by the invariance of relevant statistics (mean, standard deviation, z-score, and t-test) under changes of the spatial and temporal reference coordinate system. With all images from one time point, a cross-sectional inter-subject morphometry determined group differences between alcoholics and normal controls. We compared these results with longitudinal intra-subject morphometry based on two images per subject acquired at different times (approximately 2 years apart). Inter- and intra-subject analysis produced partially conflicting results. Whereas the intra-subject analysis indicated faster ventricular volume increases in the alcoholics (+11% per year) than in the controls (+2% per year), the inter-subject analysis showed, on average, smaller absolute ventricle volumes in the alcoholics than in the controls (-33% relative volume). These differences were confirmed by manual planimetry and were statistically significant whether tested based on difference or change, integrated over the volume of the ventricles. Other changes and group differences were consistent between the two analyses, e.g., reduction of white matter (including corpus callosum) and increase in CSF volume, and these are in agreement with established effects of alcoholism on brain structure. We conclude that intra-subject morphometry of longitudinal data is preferable to inter-subject morphometry for detecting dynamic changes due to a disease, especially when only small samples are available. Our analysis demonstrates that the distinction between group differences observed at a point in time vs. over time is not merely academic but can substantially reduce the validity of the outcomes of actual morphometric studies. This discrepancy in results underscores the importance of distinguishing between volume differences and volume changes in morphometric analyses.

Supratentorial profile of white matter microstructural integrity in recovering alcoholic men and women

BACKGROUND

Postmortem and in vivo studies consistently report degeneration of brain white matter in alcohol-dependent men and women. The full extent of the white matter involvement in uncomplicated alcoholism, however, is unknown, yet knowledge of the distribution of white matter degradation might provide clues to mechanisms underlying the pathology.

METHODS

To examine whether the white matter involvement is widespread or, alternatively, is regionally restricted in uncomplicated alcoholism, we used in vivo magnetic resonance diffusion tensor imaging (DTI) to quantify the microstructure of brain tissue. Accordingly, we acquired DTI data in 57 alcoholics (40 men, 17 women) who had been sober, on average, for 3 months and 74 demographically-matched control subjects (32 men, 42 women). Alcoholic men had consumed about twice as much alcohol in their lifetimes as the alcoholic women. Supratentorial white matter fractional anisotropy (FA), a DTI measure of intravoxel orientational coherence of tissue, was calculated across the full anterior-posterior extent of the brain in coronal sections, and a slice profile of the mean white matter FA was created for each subject. Group differences between alcoholics and control subjects were tested for each slice in three regions: the left and right hemispheres and a midsagittal sample; men and women were tested separately.

RESULTS

Alcoholic men and women each showed widespread FA deficits in all three regions relative to their gender-matched control subjects that were evident on a slice-by-slice basis. Furthermore, the number of slices showing FA deficits was significantly greater in the alcoholic men than women.

CONCLUSIONS

The widespread distribution of white matter deficits is in contrast to the highly regional-specific deficits seen in nutritional deficiency syndromes that can accompany alcoholism.

Effect of vision, touch and stance on cerebellar vermian-related sway and tremor: a quantitative physiological and MRI study

Postural balance is impaired in individuals with pathology of the anterior superior vermis of the cerebellum. Chronic alcoholism, with its known vermian pathology, provides a viable model for studying the relationship between cerebellar pathology and postural stability. Decades of separate study of recovering alcoholics and post-mortem neuroanatomical analysis have demonstrated vermian pathology but few studies have used quantitative posturography, acquired concurrently with quantitative neuroimaging, to establish whether this brain structure-function relationship is selective in vivo. Here, 30 healthy men and 39 chronic alcoholic men, abstinent from alcohol for several months, underwent MRI for volumetric quantitation of the cerebellar vermis and three comparison brain regions, the cerebellar hemispheres, supratentorial cortex and corpus callosum. All subjects also participated in an experiment involving a force platform that measured sway path length and tremor during static standing balance under four sensory conditions and two stance conditions. Three novel findings emerged: (i) sway path length, a physiological index of postural control, was selectively related to volume of the cerebellar vermis and not to any comparison brain region in the alcoholics; (ii) spectral analysis revealed sway prominence in the 2-5 Hz band, another physiological sign of vermian lesions and also selectively related to vermian volume in the alcoholics; and (iii) despite substantial postural sway in the patients, they successfully used vision, touch and stance to normalize sway and reduce tremor. The selective relationship of sway path to vermian but not lateral cerebellar volume provides correlational evidence for functional differentiation of these cerebellar regions. Improvement to virtual normal levels in balance and reduction in sway and tremor with changes in vision, touch and stance provide evidence that adaptive mechanisms recruiting sensorimotor integration can be invoked to compensate for underlying cerebellar vermian-related dysfunction.

Selective Age-related Degradation of Anterior Callosal Fiber Bundles Quantified In Vivo with Fiber Tracking

The corpus callosum, the principal white matter structure enabling interhemispheric information transfer, is heterogeneous in its microstructural composition, heterotopic in its anteroposterior cortical connectivity, and differentially susceptible to aging. In vivo characterization of callosal features is possible with diffusion tensor imaging (DTI), a magnetic resonance imaging method sensitive to the detection of white matter's linear structure. We implemented a quantitative fiber tracking approach to examine age-related variation in regional microstructural characteristics [fractional anisotropy (FA) and apparent diffusion coefficient (ADC)] of callosal fibers in 10 younger (29 +/- 5 years) and 10 older (72 +/- 5 years) healthy adults. Fiber tracking was performed on 2.5 mm isotropic voxels collected at 3 T. Fiber targets comprised the midsagittal corpus callosum, divided into six regions based on known callosal anatomical projections. FA and ADC for each voxel of each fiber identified were determined; lower FA and higher ADC reflect degraded microstructural tissue integrity. Older subjects had lower FA (P < 0.002), higher ADC (P < 0.006), and fewer (P < 0.005) fibers than younger subjects. Group x region interactions indicated disproportionately lower FA (P = 0.0001) and higher ADC (P < 0.006) in the older than younger group in frontal fiber bundles relative to posterior bundles. As a test of the functional significance of the fiber bundle metrics, the older subjects were administered the Stroop Task, which showed significant correlations between regional fiber bundle integrity and performance. These results validate this quantitative fiber tracking approach and confirm the selective vulnerability of frontal white matter systems to normal aging, likely substrates of age-related declines in cognitive processes dependent on prefrontal circuitry integrity.

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.

Striatal and forebrain nuclei volumes: contribution to motor function and working memory deficits in alcoholism

BACKGROUND

Striatal structures are involved in dopaminergic alcohol reward mechanisms and aspects of motor control. Basal forebrain structures hold cholinergic mechanisms influencing memory formation, vulnerable to chronic alcoholism; however, alcoholism's effect on volumes of these structures has seldom been considered with in vivo measurement.

METHODS

We measured bilateral volumes of caudate nucleus, putamen, nucleus accumbens, and medial septal/diagonal band (MS/DB) in 25 men with alcohol dependence and 51 age-matched control men. Six alcoholic subjects had been drinking recently, and 19 had been sober.

RESULTS

Volumes of caudate and putamen were smaller in the alcoholics than in the control subjects, regardless of length of sobriety. Recent drinkers showed greater deficits in nucleus accumbens than sober alcoholics. Putamen volume was positively correlated with grip strength; MS/DB volume was positively correlated with verbal working memory independently of the negative association between age-standardized MS/DB and age in alcoholics.

CONCLUSIONS

Caudate and putamen volume deficits occur and endure in chronic alcoholism. Nucleus accumbens might be especially sensitive to recent alcohol exposure. Striatal volumes should be considered in functional imaging studies of alcohol craving that target striatal brain regions. The age-alcohol interaction for MS/DB volumes is consistent with a cholinergic mechanism for the working memory impairment observed in the alcoholics.

Chronic active heavy drinking and family history of problem drinking modulate regional brain tissue volumes

The goals of this study were to measure if chronic active heavy drinking is associated with brain volume loss in non-treatment seeking men and women, and to assess the effect of positive family history of problem drinking on brain structure in heavy drinkers. Automated image processing was used to analyze high-resolution T1-weighted magnetic resonance images from 49 active heavy drinkers and 49 age- and sex-matched light drinkers, yielding gray matter, white matter and cerebrospinal fluid (CSF) volumes within the frontal, temporal, parietal and occipital lobes. Regional brain volume measures were compared as a function of group, sex and their interaction. Within heavy drinkers, volumes were correlated with measures of alcohol consumption and compared as a function of family history of problem drinking. Deformation morphometry explored localized patterns of atrophy associated with heavy drinking or severity of drinking. We found significant gray matter volume losses, but no white matter losses, in active heavy drinkers compared with light drinkers. Women had greater gray matter and smaller white matter and CSF volumes as a percentage of intracranial vault than men. Within heavy drinkers, smaller gray matter volumes were associated with higher current levels of drinking and older age, while a positive family history of problem drinking was associated with smaller CSF volumes. Community-dwelling heavy drinkers who are not in alcoholism treatment have dose-related gray matter volume losses, and family history of problem drinking ameliorates some structural consequences of heavy drinking.

Disruption of brain white matter microstructure by excessive intracellular and extracellular fluid in alcoholism: evidence from diffusion tensor imaging

Magnetic resonance diffusion tensor imaging (DTI) has revealed the disruption of brain white matter microstructure in normal aging and alcoholism undetectable with conventional structural MR imaging. The metrics of DTI can be useful in establishing the nature of the observed microstructural aberrations. Abnormally low fractional anisotropy (FA), a measure of diffusion orientation and coherence, may result from increased intracellular or extracellular fluid, which would be reflected in complementary high apparent diffusion coefficients (bulk mean diffusivity) and low FA, or from disorganization of fiber structure, which would be reflected in low FA but with a lack of the inverse FA and diffusivity relationship. To test these competing possibilities, we examined 15 alcoholic men and 31 control men with DTI to quantify diffusivity in the genu and splenium of the corpus callosum and centrum semiovale. In addition to the previously observed FA deficits in all the three brain regions, the alcoholics had abnormally high white matter diffusivity values in the genu and centrum. Further, inverse correlations between FA and diffusivity were significant in the genu (r=-0.52, p<0.05) and centrum (r=-0.92, p=0.0001). Multiple regression analyses examining diffusivity and age as predictors of FA identified diffusivity as a significant unique contributor to FA in both regions. These results suggest that decreased orientational coherence of brain white matter in alcoholism is attributable, at least in part, to the accumulation of intracellular and extracellular fluid in excess of that occurring in aging, and that the differential influence of these fluid compartments can vary across brain regions.

Corpus callosal microstructural integrity influences interhemispheric processing: a diffusion tensor imaging study

Normal aging and chronic alcoholism result in disruption of brain white matter microstructure that does not typically cause complete lesions but may underlie degradation of functions requiring interhemispheric information transfer. We examined whether the microstructural integrity of the corpus callosum assessed with diffusion tensor imaging (DTI) would relate to interhemispheric processing speed. DTI yields estimates of fractional anisotropy (FA), a measure of orientation and intravoxel coherence of water diffusion usually in white matter fibers, and diffusivity (<D>), a measure of the amount of intracellular and extracellular fluid diffusion. We tested the hypothesis that FA and <D> would be correlated with (i) the crossed-uncrossed difference (CUD), testing visuomotor interhemispheric transfer; and (ii) the redundant targets effect (RTE), testing parallel processing of visual information presented to each cerebral hemisphere. FA was lower and <D> higher in alcoholics than in controls. In controls but not alcoholics, large CUDs correlated with low FA and high <D> in total corpus callosum and regionally in the genu and splenium. In alcoholics but not controls, small RTEs, elicited with equiluminant stimuli, correlated with low FA in genu and splenium and high <D> in the callosal body. The results provide in vivo evidence for disruption of corpus callosum microstructure in normal aging and alcoholism that has functional ramifications for efficiency in interhemispheric processing.

Information fusion in biomedical image analysis: combination of data vs. combination of interpretations

Information fusion has, in the form of multiple classifier systems, long been a successful tool in pattern recognition applications. It is also becoming increasingly popular in biomedical image analysis, for example in computer-aided diagnosis and in image segmentation. In this paper, we extend the principles of multiple classifier systems by considering information fusion of classifier inputs rather than on their outputs, as is usually done. We introduce the distinction between combination of data (i.e., classifier inputs) vs. combination of interpretations (i.e., classifier outputs). We illustrate the two levels of information fusion using four different biomedical image analysis applications that can be implemented using fusion of either data or interpretations: atlas-based image segmentation, "average image" tissue classification, multi-spectral classification, and deformation-based group morphometry.

Abnormal EEG synchronisation in heavily drinking students

OBJECTIVE

In alcoholics, grey and white brain matter is damaged. In addition, functional brain connectivity as measured by EEG coherence is abnormal. We investigated whether heavily drinking students, although drinking for a shorter period than alcoholics, already show differences in functional connectivity compared to light-drinking controls.

METHODS

EEG was recorded in 11 light and 11 heavy male student drinkers during eyes closed, and eyes closed plus mental rehearsal of pictures. Functional connectivity was assessed with the Synchronisation Likelihood method.

RESULTS

Heavily drinking students had more synchronisation in the theta (4-8 Hz) and gamma (30-45 Hz) band than lightly drinking students during eyes closed, both with and without a mental-rehearsal task.

CONCLUSIONS

Heavy student drinkers have increases in EEG synchronisation that are indicative of changes in hippocampal-neocortical connectivity.

SIGNIFICANCE

Heavy student drinkers show differences in functional connectivity as compared to their lightly drinking counterparts, even though they have a relatively short drinking history.

Compromised pontocerebellar and cerebellothalamocortical systems: speculations on their contributions to cognitive and motor impairment in nonamnesic alcoholism

BACKGROUND

Corticopontocerebellar and cerebellothalamocortical circuits underlie a wide range of neuropsychological processes compromised by alcoholism. The analyses herein tested whether abnormalities of volumes of brain structures forming nodes of these separate feed-forward and feedback systems are selectively related to each other and whether any of these noncortical regions can account for cognitive and motor deficits occurring as sequelae of chronic alcoholism.

METHODS

Regional brain measures originated from our prior neuroimaging studies, showing in alcoholics significant volume deficits in the principal structures of interest: cerebellar hemispheres, vermis, pons, and thalamus as well as prefrontal, frontal, and parietal cortex. Neuropsychological functions targeted for analysis-problem solving, visuospatial ability, and static postural stability-showed 0.6 to 1.6 SD deficits in these alcoholic men.

RESULTS

In alcoholics, the patterns of correlations were consistent with dissociation of thalamic and pontine circuitry. Pontine and thalamic volumes were not correlated with each other. Pontine volumes correlated with white matter volumes of anterior superior vermis and gray and white matter volumes of the cerebellar hemispheres but not with cortical regional volumes. Thalamic volumes correlated with gray matter volumes of the cerebellar hemispheres, parietal cortex, and inferior posterior vermian lobule, which itself correlated with parietal, prefrontal, and frontal cortical volumes. Controls did not show these correlational patterns. Brain structure-function relationships in alcoholics examined with multiple regression identified anterior vermian but not prefrontal or parietal volume as a unique predictor of balance scores; vermian and thalamic but not prefrontal cortical volumes as predictors of card sorting scores; and cerebellar hemispheric white matter but not parietal cortical volume as a predictor of visuospatial ability.

CONCLUSIONS

Each major node of frontocerebellar circuitry shows volume deficits in alcoholics but can be independently compromised. Disruption of these circuits may underlie alcoholism-related neuropsychological deficits, either by abnormalities present in individual nodes or by disconnection via interruption of selective circuitry.

Effects of age and sex on volumes of the thalamus, pons, and cortex

Volumes of thalamus, pons, cortical gray matter, and white matter were derived from MR brain images of healthy men and women spanning the adult age range in order to delineate patterns of aging and to compare age and sex effects in thalamus and pons with such effects in cortical gray and white matter volumes. Men had larger intracranial volume (ICV) than women, but ICV did not correlate with age in either sex. Thalamic, pontine, and cortical white matter volumes did not differ between men and women once ICV differences were taken into account, but men had more cortical gray matter than women even after accounting for ICV. Volumes of pons and thalamus were associated, independent of ICV, in women but not in men. Thalamic volume declined linearly with age at a similar rate in both men and women, whereas cortical gray matter volume declined more steeply with age in men than women. Both pontine and cortical white matter volumes remained stable across the age span in both men and women.