Changes in the basal dendrites of cortical pyramidal cells from alcoholic patients--a quantitative Golgi study

Historical review: The golden age of the Golgi method in human neuropathology

Golgi methods were used to study human neuropathology in the 1970s, 1980s, and 1990s of the last century. Although a relatively small number of laboratories applied these methods, their impact was crucial by increasing knowledge about: (1) the morphology, orientation, and localization of neurons in human cerebral and cerebellar malformations and ganglionic tumors, and (2) the presence of abnormal structures including large and thin spines (spine dysgenesis) in several disorders linked to mental retardation, focal enlargements of the axon hillock and dendrites (meganeurites) in neuronal storage diseases, growth cone-like appendages in Alzheimer disease, as well as abnormal structures in other dementias. Although there were initial concerns about their reliability, reduced dendritic branches and dendritic spines were identified as common alterations in mental retardation, dementia, and other pathological conditions. Similar observations in appropriate experimental models have supported many abnormalities that were first identified using Golgi methods in human material. Moreover, electron microscopy, immunohistochemistry, fluorescent tracers, and combined methods have proven the accuracy of pioneering observations uniquely visualized as 3D images of fully stained individual neurons. Although Golgi methods had their golden age many years ago, these methods may still be useful complementary tools in human neuropathology.

Areas of Convergence and Divergence in Adolescent Social Isolation and Binge Drinking: A Review

Adolescence is a critical developmental period characterized by enhanced social interactions, ongoing development of the frontal cortex and maturation of synaptic connections throughout the brain. Adolescents spend more time interacting with peers than any other age group and display heightened reward sensitivity, impulsivity and diminished inhibitory self-control, which contribute to increased risky behaviors, including the initiation and progression of alcohol use. Compared to adults, adolescents are less susceptible to the negative effects of ethanol, but are more susceptible to the negative effects of stress, particularly social stress. Juvenile exposure to social isolation or binge ethanol disrupts synaptic connections, dendritic spine morphology, and myelin remodeling in the frontal cortex. These structural effects may underlie the behavioral and cognitive deficits seen later in life, including social and memory deficits, increased anxiety-like behavior and risk for alcohol use disorders (AUD). Although the alcohol and social stress fields are actively investigating the mechanisms through which these effects occur, significant gaps in our understanding exist, particularly in the intersection of the two fields. This review will highlight the areas of convergence and divergence in the fields of adolescent social stress and ethanol exposure. We will focus on how ethanol exposure or social isolation stress can impact the development of the frontal cortex and lead to lasting behavioral changes in adulthood. We call attention to the need for more mechanistic studies and the inclusion of the evaluation of sex differences in these molecular, structural, and behavioral responses.

Chronic intermittent ethanol during adolescence and adulthood alters dendritic spines in the primary motor and visual cortex in rats

Prolonged adolescent binge drinking can disrupt sleep quality and increase the likelihood of alcohol-induced sleep disruptions in young adulthood in rodents and in humans. Striking changes in spine density and morphology have been seen in many cortical and subcortical regions after adolescent alcohol exposure in rats. However, there is little known about the impact of alcohol exposure on dendritic spines in the same motor and sensory cortices that EEG sleep is typically recorded from in rats. The aim of this study is to investigate whether an established model of chronic intermittent ethanol vapor in rats that has been demonstrated to disrupt sleep during adolescence or adulthood, also significantly alters cortical dendritic spine density and morphology. To this end, adolescent and adult Wistar rats were exposed to 5 weeks of ethanol vapor or control air exposure. After a 13-day withdrawal, primary motor cortex (M1) and primary/secondary visual cortex (V1/V2) layer V dendrites were analyzed for differences in spine density and morphology. Spines were classified into four categories (stubby, long, filopodia, and mushroom) based on the spine length and the width of the spine head and neck. The main results indicate an age-specific effect of adolescent intermittent ethanol exposure decreasing spine density in the M1 cortex compared to age-matched controls. Reductions in the density of M1 long-shaped spine subclassifications were seen in adolescent ethanol-exposed rats, but not adult-exposed rats, compared to their air-controls. Irrespective of age, there was an overall reduction produced by ethanol exposure on the density of filopodia and the length of long-shaped spines in V1/V2 cortex as compared to their air-exposed controls. Together, these data add to growing evidence that some cortical circuits are vulnerable to the effects of alcohol during adolescence and begin to elucidate potential mechanisms that may influence brain plasticity following early alcohol use.

Alcohol Consumption, Brain Amyloid-β Deposition, and Brain Structural Integrity Among Older Adults Free of Dementia

BACKGROUND

Light to moderate alcohol consumption has been variably associated with lower or higher risk of dementia, but effects on Alzheimer's disease pathology are less clear.

OBJECTIVE

We determined whether late-life alcohol consumption was associated with Alzheimer's disease pathology among older adults.

METHODS

We assessed the associations of alcohol consumption self-reported in 2000-2002 with brain amyloid-β deposition on PET scans, and white matter lesion and hippocampal volume on MRIs measured 7-9 years later in 189 participants of the Ginkgo Evaluation of Memory Study (age 75-87 years at baseline) who were free of clinical dementia, using multivariable-adjusted and inverse probability-weighted robust linear regression models.

RESULTS

Alcohol consumption was not statistically significantly associated with amyloid-β deposition (standardized uptake value ratio difference per drink: -0.013 [95% CI: -0.027, 0.002]). Both non-drinkers and participants consuming ≥1 drink(s)/week had higher white matter lesion volume (% intracranial volume) than did the reference group of those consuming <1 drink/week (differences: 0.25 % [95% CI: 0.01, 0.50]; 0.26 % [95% CI: 0.02, 0.50]). The association of alcohol consumption and hippocampal volume was modified by age (p = 0.02). Among participants younger than 77 years, participants consuming 1-7 drinks/week had larger hippocampal volume compared with participants consuming <1 drink/week.

CONCLUSIONS

Alcohol consumption was not statistically significantly associated with amyloid-β deposition 7-9 years later. Non-drinking and greater alcohol consumption were associated with higher white matter lesion volume compared with drinking <1 drink/week. Moderate drinking was associated with higher hippocampal volume in younger individuals. Given the selective nature of this population and adverse health effects of excessive alcohol consumption, these findings warrant further investigation, but cannot be translated into clinical recommendations.

Sex and Age Effects on Neurobehavioral Toxicity Induced by Binge Alcohol

Historically, most alcohol neurotoxicity studies were conducted in young adult males and focused on chronic intake. There has been a shift towards studying the effects of alcohol on the adolescent brain, due to alcohol consumption during this formative period disrupting the brain's developmental trajectory. Because the most typical pattern of adolescent alcohol intake is heavy episodic (binge) drinking, there has also been a shift towards the study of binge alcohol-induced neurobehavioral toxicity. It has thus become apparent that binge alcohol damages the adolescent brain and there is increasing attention to sex-dependent effects. Significant knowledge gaps remain in our understanding of the effects of binge alcohol on the female brain, however. Moreover, it is unsettling that population-level studies indicate that the prevalence of binge drinking is increasing among American women, particularly those in older age groups. Although study of adolescents has made it apparent that binge alcohol disrupts ongoing brain maturational processes, we know almost nothing about how it impacts the aging brain, as studies of its effects on the aged brain are relatively scarce, and the study of sex-dependent effects is just beginning. Given the rapidly increasing population of older Americans, it is crucial that studies address age-dependent effects of binge alcohol, and given the increase in binge drinking in older women who are at higher risk for cognitive decline relative to men, studies must encompass both sexes. Because adolescence and older age are both characterized by age-typical brain changes, and because binge drinking is the most common pattern of alcohol intake in both age groups, the knowledge that we have amassed on binge alcohol effects on the adolescent brain can inform our study of its effects on the aging brain. In this review, we therefore cover the current state of knowledge of sex and age-dependent effects of binge alcohol, as well as statistical and methodological considerations for studies aimed at addressing them.

Review of Orbitofrontal Cortex in Alcohol Dependence: A Disrupted Cognitive Map?

Alcoholism is a persistent worldwide problem associated with long-lasting impairments to decision making processes. Some aspects of dysfunction are thought to reflect alcohol-induced changes to relevant brain areas such as the orbitofrontal cortex (OFC). In this review, we will examine how chronic alcohol exposure alters OFC function to potentially contribute to maladaptive decision making, and explore experimental behavioral approaches that may be better suited to test whether alcohol dependence disrupts OFC's function. We argue that although past works suggest impairments in aspects of OFC function, more information may be gained by specifically targeting tasks to the broader function of OFC as put forth by the recent hypothesis of OFC as a "cognitive map" of task space. Overall, we suggest that such a focus could provide a better understanding of how OFC function changes in alcohol dependence, and could inform better assessment tools and treatment options for clinicians working with this population.

Its complicated: The relationship between alcohol and microglia in the search for novel pharmacotherapeutic targets for alcohol use disorders

Alcohol use disorder (AUD) is a chronic relapsing disorder with wide-ranging health consequences. Alcohol targets the central nervous system producing neurodegeneration and subsequent cognitive and behavioral deficits, but the mechanisms behind these effects remain unclear. Recently, evidence has been mounting for the role of neuroimmune activation in the pathogenesis of AUDs, but our nascent state of knowledge about the interaction of alcohol with the neuroimmune system supports that the relationship is complicated. As the resident macrophage of the central nervous system, microglia are a central focus. Human and animal research on the interplay between microglia and alcohol in AUDs has proven to be complex, and though early research focused on a pro-inflammatory phenotype of microglia, the anti-inflammatory and homeostatic roles of microglia must be considered. How these new roles for microglia should be incorporated into our thinking about the neuroimmune system in AUDs is discussed in the context of developing novel pharmacotherapies for AUDs.

The Interplay of Inflammatory Processes and Cognition in Alcohol Use Disorders-A Systematic Review

Rationale: Of late, evidence emerges that the pathophysiology of psychiatric diseases and their affiliated symptomatologies are at least partly contributable to inflammatory processes. Also in alcohol use disorders (AUD), this interaction is strongly apparent, with severely immunogenic liver cirrhosis being one of the most critical sequelae of chronic abusive drinking. This somatic immune system activation negatively impacts brain functioning, and additionally, alcohol abuse appears to have a direct detrimental effect on the brain by actively stimulating its immune cells and responses. As cognitive decline majorly contributes to AUD's debility, it is important to know to what extent impairment of cognitive functioning is due to these (neuro-)inflammatory aberrations. Method: We hereby summarize the current existing literature on the interplay between AUD, inflammation, and cognition in a systematic review according to the PRISMA-P guidelines for the systematic review. Main findings: Although literature on the role of inflammation in alcohol use-related cognitive deficiency remains scarce, current findings indicate that pro-inflammatory processes indeed result in exacerbation of several domains of cognitive deterioration. Interestingly, microglia, the immune cells of the brain, appear to exert initial compensatory neuroprotective functionalities upon acute ethanol exposure while chronic alcohol intake seems to attenuate these responses and overall microglial activity. Conclusion: As these results indicate inflammation to be of importance in cognitive impairment following alcohol consumption and might as such provide alternate therapeutic avenues, a considerable increase in research efforts in this domain is urgently required.

Decreased subcortical volumes in alcohol dependent individuals: effect of polysubstance use disorder

Chronic alcohol use has widespread effects on brain morphometry. Alcohol dependent individuals are often diagnosed with comorbid substance use disorders. Alterations in brain morphometry may be different in individuals that are dependent on alcohol alone and individuals dependent on alcohol and other substances. We examined subcortical brain volumes in 37 individuals with alcohol dependence only (ADO), 37 individuals with polysubstance use disorder (PS) and 37 healthy control participants (HC). Participants underwent a structural MR scan and a model-based segmentation tool was used to measure the volume of 14 subcortical regions (bilateral thalamus, caudate, putamen, globus pallidus, hippocampus, amygdala and nucleus accumbens). Compared to HC, ADO had smaller volume in the bilateral hippocampus, right nucleus accumbens and right thalamus. PS only had volume reductions in the bilateral thalamus compared to HC. PS had a larger right caudate compared to ADO. Subcortical volume was negatively associated with drinking measures only in the ADO group. This study confirms the association between alcohol dependence and reductions in subcortical brain volume. It also suggests that polysubstance use interacts with alcohol use to produce limited subcortical volume reduction and at least one region of subcortical volume increase. These findings indicate that additional substance use may mask damage through inflammation or may function in a protective manner, shielding subcortical regions from alcohol-induced damage.

Korsakoff's syndrome: a critical review

In this review, we present a survey on Korsakoff's syndrome (KS), a residual syndrome in patients who suffered from a Wernicke encephalopathy (WE) that is predominantly characterized by global amnesia, and in more severe cases also by cognitive and behavioral dysfunction. We describe the history of KS and its definition, its epidemiology, and the lack of consensus criteria for its diagnosis. The cognitive and behavioral symptoms of KS, which include anterograde and retrograde amnesia, executive dysfunction, confabulation, apathy, as well as affective and social-cognitive impairments, are discussed. Moreover, recent insights into the underlying neurocognitive mechanisms of these symptoms are presented. In addition, the evidence so far on the etiology of KS is examined, highlighting the role of thiamine and alcohol and discussing the continuity hypothesis. Furthermore, the neuropathology of KS is reviewed, focusing on abnormalities in the diencephalon, including the mammillary bodies and thalamic nuclei. Pharmacological treatment options and nonpharmacological interventions, such as those based on cognitive rehabilitation, are discussed. Our review shows that thiamine deficiency (TD) is a crucial factor in the etiology of KS. Although alcohol abuse is by far the most important context in which TD occurs, there is no convincing evidence for an essential contribution of ethanol neurotoxicity (EN) to the development of WE or to the progression of WE to KS. Future research on the postmortem histopathological analysis of brain tissues of KS patients is crucial for the advancement of our knowledge of KS, especially for associating its symptoms with lesions in various thalamic nuclei. A necessary requirement for the advancement of studies on KS is the broad acceptance of a comprehensive definition and definite diagnostic criteria. Therefore, in this review, we propose such a definition of KS and draft outlines for prospective diagnostic criteria.

Prefrontal Cortical Thickness Deficit in Detoxified Alcohol-dependent Patients

Alcohol dependence is a serious disorder that can be related with a number of potential health-related and social consequences. Cortical thickness measurements would provide important information on the cortical structural alterations in patients with alcohol dependence. Twenty-one patients with alcohol dependence and 22 healthy comparison subjects have been recruited and underwent high-resolution brain magnetic resonance (MR) imaging and clinical assessments. T1-weighted MR images were analyzed using the cortical thickness analysis program. Significantly thinner cortical thickness in patients with alcohol dependence than healthy comparison subjects was noted in the left superior frontal cortical region, correcting for multiple comparisons and adjusting with age and hemispheric average cortical thickness. There was a significant association between thickness in the cluster of the left superior frontal cortex and the duration of alcohol use. The prefrontal cortical region may particularly be vulnerable to chronic alcohol exposure. It is also possible that the pre-existing deficit in this region may have rendered individuals more susceptible to alcohol dependence.

The importance of mammillary body efferents for recency memory: towards a better understanding of diencephalic amnesia

Despite being historically one of the first brain regions linked to memory loss, there remains controversy over the core features of diencephalic amnesia as well as the critical site for amnesia to occur. The mammillary bodies and thalamus appear to be the primary locus of pathology in the cases of diencephalic amnesia, but the picture is complicated by the lack of patients with circumscribed damage. Impaired temporal memory is a consistent neuropsychological finding in Korsakoff syndrome patients, but again, it is unclear whether this deficit is attributable to pathology within the diencephalon or concomitant frontal lobe dysfunction. To address these issues, we used an animal model of diencephalic amnesia and examined the effect of mammillothalamic tract lesions on tests of recency memory. The mammillothalamic tract lesions severely disrupted recency judgements involving multiple items but left intact both recency and familiarity judgements for single items. Subsequently, we used disconnection procedures to assess whether this deficit reflects the indirect involvement of the prefrontal cortex. Crossed-lesion rats, with unilateral lesions of the mammillothalamic tract and medial prefrontal cortex in contralateral hemispheres, were unimpaired on the same recency tests. These results provide the first evidence for the selective importance of mammillary body efferents for recency memory. Moreover, this contribution to recency memory is independent of the prefrontal cortex. More broadly, these findings identify how specific diencephalic structures are vital for key elements of event memory.

The effects of chronic smoking on the pathology of alcohol-related brain damage

Both pathological and neuroimaging studies demonstrate that chronic alcohol abuse causes brain atrophy with widespread white matter loss limited gray matter loss. Recent neuroimaging studies suggest that tobacco smoking also causes brain atrophy in both alcoholics and neurologically normal individuals; however, this has not been confirmed pathologically. In this study, the effects of smoking and the potential additive effects of concomitant alcohol and tobacco consumption were investigated in autopsied human brains. A total of 44 cases and controls were divided into four groups: 16 non-smoking controls, nine smoking controls, eight non-smoking alcoholics, and 11 smoking alcoholics. The volumes of 26 gray and white matter regions were measured using an established point-counting technique. The results showed trends for widespread white matter loss in alcoholics (p < 0.007) but no effect on gray matter regions. In contrast, smoking alone had no effect on brain atrophy and the combination of smoking and alcohol showed no additional effect. Neuronal density was analyzed as a more sensitive assay of gray matter integrity. Similar to the volumetric analysis, there was a reduction in neurons (29%) in the prefrontal cortex of alcoholics, albeit this was only a trend when adjusted for potential confounders (p < 0.06). There were no smoking or combinatorial effects on neuronal density in any of the three regions examined. These results do not support the hypothesis that smoking exacerbates alcohol-related brain damage. The trends here support previous studies that alcohol-related brain damage is characterized by focal neuronal loss and generalized white matter atrophy. These disparate effects suggest that two different pathogenic mechanisms may be operating in the alcoholic brain. Future studies using ultrastructural or molecular techniques will be required to determine if smoking has more subtle effects on the brain and how chronic alcohol consumption leads to widespread white matter loss.

Withdrawal from chronic intermittent alcohol exposure increases dendritic spine density in the lateral orbitofrontal cortex of mice

Alcohol use disorders (AUDs) are associated with functional and morphological changes in subfields of the prefrontal cortex. Clinical and preclinical evidence indicates that the orbitofrontal cortex (OFC) is critical for controlling impulsive behaviors, representing the value of a predicted outcome, and reversing learned associations. Individuals with AUDs often demonstrate deficits in OFC-dependent tasks, and rodent models of alcohol exposure show that OFC-dependent behaviors are impaired by chronic alcohol exposure. To explore the mechanisms that underlie these impairments, we examined dendritic spine density and morphology, and NMDA-type glutamate receptor expression in the lateral OFC of C57BL/6J mice following chronic intermittent ethanol (CIE) exposure. Western blot analysis demonstrated that NMDA receptors were not altered immediately following CIE exposure or after 7 days of withdrawal. Morphological analysis of basal dendrites of layer II/III pyramidal neurons revealed that dendritic spine density was also not affected immediately after CIE exposure. However, the total density of dendritic spines was significantly increased after a 7-day withdrawal from CIE exposure. The effect of withdrawal on spine density was mediated by an increase in the density of long, thin spines with no change in either stubby or mushroom spines. These data suggest that morphological neuroadaptations in lateral OFC neurons develop during alcohol withdrawal and occur in the absence of changes in the expression of NMDA-type glutamate receptors. The enhanced spine density that follows alcohol withdrawal may contribute to the impairments in OFC-dependent behaviors observed in CIE-treated mice.

Postdependent state in rats as a model for medication development in alcoholism

Rational development of novel therapeutic strategies for alcoholism requires understanding of its underlying neurobiology and pathophysiology. Obtaining this knowledge largely relies on animal studies. Thus, choosing the appropriate animal model is one of the most critical steps in pre-clinical medication development. Among the range of animal models that have been used to investigate excessive alcohol consumption in rodents, the postdependent model stands out. It was specifically developed to test the role of negative affect as a key driving force in a perpetuating addiction cycle for alcoholism. Here, we will describe our approach to make rats dependent via chronic intermittent exposure to alcohol, discuss the validity of this model, and compare it with other commonly used animal models of alcoholism. We will summarize evidence that postdependent rats fulfill several criteria of a 'Diagnostic and Statistical Manual of Mental Disorders IV/V-like' diagnostic system. Importantly, these animals show long-lasting excessive consumption of and increased motivation for alcohol, and evidence for loss of control over alcohol intake. Our conclusion that postdependent rats are an excellent model for medication development for alcoholism is underscored by a summary of more than two dozen pharmacological tests aimed at reversing these abnormal alcohol responses. We will end with open questions on the use of this model. In the tradition of the Sanchis-Segura and Spanagel review, we provide comic strips that illustrate the postdependent procedure and relevant phenotypes in this review.

Microglial proliferation in the brain of chronic alcoholics with hepatic encephalopathy

Hepatic encephalopathy (HE) is a common complication of chronic alcoholism and patients show neurological symptoms ranging from mild cognitive dysfunction to coma and death. The HE brain is characterized by glial changes, including microglial activation, but the exact pathogenesis of HE is poorly understood. During a study investigating cell proliferation in the subventricular zone of chronic alcoholics, a single case with widespread proliferation throughout their adjacent grey and white matter was noted. This case also had concomitant HE raising the possibility that glial proliferation might be a pathological feature of the disease. In order to explore this possibility fixed postmortem human brain tissue from chronic alcoholics with cirrhosis and HE (n = 9), alcoholics without HE (n = 4) and controls (n = 4) were examined using immunohistochemistry and cytokine assays. In total, 4/9 HE cases had PCNA- and a second proliferative marker, Ki-67-positive cells throughout their brain and these cells co-stained with the microglial marker, Iba1. These cases were termed 'proliferative HE' (pHE). The microglia in pHEs displayed an activated morphology with hypertrophied cell bodies and short, thickened processes. In contrast, the microglia in white matter regions of the non-proliferative HE cases were less activated and appeared dystrophic. pHEs were also characterized by higher interleukin-6 levels and a slightly higher neuronal density . These findings suggest that microglial proliferation may form part of an early neuroprotective response in HE that ultimately fails to halt the course of the disease because underlying etiological factors such as high cerebral ammonia and systemic inflammation remain.

CNS proteomes in alcohol and drug abuse and dependence

Drugs of abuse, including alcohol, can induce dependency formation and/or brain damage in brain regions important for cognition. 'High-throughput' approaches, such as cDNA microarray and proteomics, allow the analysis of global expression profiles of genes and proteins. These technologies have recently been applied to human brain tissue from patients with psychiatric illnesses, including substance abuse/dependence and appropriate animal models to help understand the causes and secondary effects of these complex disorders. Although these types of studies have been limited in number and by proteomics techniques that are still in their infancy, several interesting hypotheses have been proposed. Focusing on CNS proteomics, we aim to review and update current knowledge in this rapidly advancing area.

Implicit memory in Korsakoff's syndrome: a review of procedural learning and priming studies

Korsakoff's syndrome (KS) is characterized by dense anterograde amnesia resulting from damage to the diencephalon region, typically resulting from chronic alcohol abuse and thiamine deficiency. This review assesses the integrity of the implicit memory system in KS, focusing on studies of procedural learning and priming. KS patients are impaired on several measures of procedural memory, most likely due to impairment in cognitive functions associated with alcohol-related neural damage outside of the diencephalon. The pattern of performance on tasks of implicit priming suggests reliance on a residual, non-flexible memory operating more or less in an automatic fashion. Our review concludes that whether measures of implicit memory reveal intact or impaired performance in individuals with KS depends heavily on specific task parameters and demands, including timing between stimuli, the specific nature of the stimuli used in a task, and the integrity of supportive cognitive functions necessary for performance.

Alcoholism and cellular vulnerability in different brain regions

Alcohol-induced damage causes dysfunction of selected brain regions. Multidisciplinary studies have provided an extensive description of changes observed in neurons and glia following alcohol consumption. In this study the authors have elucidated preferential cellular vulnerability in three different brain regions. Autopsy material of the prefrontal cortex, striatum, and substantia nigra obtained from the brain tissue of alcoholic subjects was used in this study. We found that dendritic tree and astroglial damage is irreversible, while neuronal somata and most axons do not display irreversible changes.

Reduced fronto-cerebellar functional connectivity in chronic alcoholic patients

BACKGROUND

Alcohol dependence is associated with neurocognitive deficits related to neuropathological changes in structure, metabolism, and function of the brain. Impairments of motor functioning in alcoholics have been attributed to well-characterized neuropathological brain abnormalities in cerebellum.

METHODS

Using functional magnetic resonance imaging (fMRI), we studied in vivo the functional connectivity between cerebellar and cortical brain regions. Participants were 10 uncomplicated chronic alcoholic patients studied after 5 to 7 days of abstinence when signs of withdrawal had abated and 10 matched healthy controls. We focused on regions of prefrontal, frontal, temporal, and parietal cortex that exhibited an fMRI response associated with nondominant hand finger tapping in the patients but not in the controls. We predicted that fronto-cerebellar functional connectivity would be diminished in alcoholics compared with controls.

RESULTS

Functional connectivity in a circuit involving premotor areas (Brodmann Area 6) and Lobule VI of the superior cerebellum was reduced in the patients compared with the controls. Functional connectivity was also reduced in a circuit involving prefrontal cortex (Brodmann Area 9) and Lobule VIII of the inferior cerebellum. Reductions in connectivity were specific to fronto-cerebellar circuits and were not found in other regions examined.

CONCLUSIONS

Our findings show a pattern in recently abstinent alcoholic patients of specific deficits in functional connectivity and recruitment of additional brain regions for the performance of a simple finger-tapping task. A small sample, differences in smoking, and a brief abstinence period preclude definitive conclusions, but this pattern of diminished fronto-cerebellar functional connectivity is highly compatible with the characteristic neuropathological lesions documented in alcoholics and may reflect brain dysfunction associated with alcoholism.

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.

Dual tasking and working memory in alcoholism: relation to frontocerebellar circuitry

Controversy exists regarding the role of cerebellar systems in cognition and whether working memory compromise commonly marking alcoholism can be explained by compromise of nodes of corticocerebellar circuitry. We tested 17 alcoholics and 31 age-matched controls with dual-task, working memory paradigms. Interference tasks competed with verbal and spatial working memory tasks using low (three item) or high (six item) memory loads. Participants also underwent structural MRI to obtain volumes of nodes of the frontocerebellar system. On the verbal working memory task, both groups performed equally. On the spatial working memory with the high-load task, the alcoholic group was disproportionately more affected by the arithmetic distractor than were controls. In alcoholics, volumes of the left thalamus and left cerebellar Crus I volumes were more robust predictors of performance in the spatial working memory task with the arithmetic distractor than the left frontal superior cortex. In controls, volumes of the right middle frontal gyrus and right cerebellar Crus I were independent predictors over the left cerebellar Crus I, left thalamus, right superior parietal cortex, or left middle frontal gyrus of spatial working memory performance with tracking interference. The brain-behavior correlations suggest that alcoholics and controls relied on the integrity of certain nodes of corticocerebellar systems to perform these verbal and spatial working memory tasks, but that the specific pattern of relationships differed by group. The resulting brain structure-function patterns provide correlational support that components of this corticocerebellar system not typically related to normal performance in dual-task conditions may be available to augment otherwise dampened performance by alcoholics.

Recruitment of additional brain regions to accomplish simple motor tasks in chronic alcohol-dependent patients

BACKGROUND

Chronic alcohol-dependent patients (ALC) exhibit neurocognitive impairments attributed to alcohol-induced fronto-cerebellar damage. Deficits are typically found in complex task performance, whereas simple tasks may not be significantly compromised, perhaps because of little understood compensatory changes.

METHODS

We compared finger tapping with either hand at externally paced (EP) or maximal self-paced (SP) rates and concomitant brain activation in ten pairs of right-hand dominant, age-, and gender-matched, severe, uncomplicated ALC and normal controls (NC) using functional magnetic resonance imaging (fMRI).

RESULTS

Mean tapping rates were not significantly different in ALC and NC for either task, but SP tapping variances were greater in ALC for both hands. SP tapping was more rapid with dominant hand (DH) than non-dominant hand (NDH) for both groups. EP and SP tapping with the non-dominant hand demonstrated significantly more activation in ALC than NC in the pre and postcentral gyri, inferior frontal gyrus, inferior parietal lobule, and the middle temporal gyrus. Areas activated only by ALC (not at all by NC) during NDH tapping included the inferior frontal gyrus, middle temporal gyrus, and postcentral gyrus. There were no significant group activation differences with DH tapping. No brain regions activated more in NC than ALC. SP tapping in contrast to EP activated fronto-cerebellar networks in NC, including postcentral gyrus, anterior cingulate, and the anterior lobe and vermis of the cerebellum, but only parietal precuneus in ALC.

CONCLUSIONS

These findings with NDH finger tapping support previous reports of neurocognitive inefficiencies in ALC. Inferior frontal activation with EP in ALC, but not in NC, suggests engagement of regions needed for planning, organization, and impulse regulation; greater contralateral parietal lobe activation with SP in ALC may reflect right hemispheric impairments in visuospatial performance. Contrasting brain activation during SP and EP suggests that ALC may not have enlisted a fronto-cerebellar network as did NC but rather employed a higher order planning mode by recruiting parietal lobe functions to attain normal mean finger tapping rates. Elucidation of the compensatory neural mechanisms that allow near normal performance by ALC on simple tasks can inform functional rehabilitation of patients in recovery.

Ethanol and cognition: indirect effects, neurotoxicity and neuroprotection: a review

Ethanol affects cognition in a number of ways. Indirect effects include intoxication, withdrawal, brain trauma, central nervous system infection, hypoglycemia, hepatic failure, and Marchiafava-Bignami disease. Nutritional deficiency can cause pellagra and Wernicke-Korsakoff disorder. Additionally, ethanol is a direct neurotoxin and in sufficient dosage can cause lasting dementia. However, ethanol also has neuroprotectant properties and in low-to-moderate dosage reduces the risk of dementia, including Alzheimer type. In fetuses ethanol is teratogenic, and whether there exists a safe dose during pregnancy is uncertain and controversial.

Postnatal binge-like alcohol exposure decreases dendritic complexity while increasing the density of mature spines in mPFC Layer II/III pyramidal neurons

Prenatal exposure to alcohol in humans can result in a wide range of deficits collectively referred to as fetal alcohol spectrum disorders. Of these deficits, cognitive impairments are among the most debilitating and long-lasting. Specifically, cognitive impairments in executive functioning suggest damage to the prefrontal cortex (PFC). Several external stimuli, such as morphine, chronic stress, and maternal stress have been found to alter the dendritic structure of cells within the PFC. In this study, three groups of rat pups were used: intubated with alcohol (5.25 g/kg/day; AE), sham intubated (SI), or suckle controls (SC) on PD 4-9. On PD 26-30 rats were anesthetized, perfused with saline and brains were processed for Golgi-Cox staining. Basilar dendritic complexity, spine density, and spine phenotypes were evaluated for Layer II/III neurons in the medial PFC. Results indicate that AE rats have an altered basilar dendritic complexity due to a significant decrease in both length and number of intersections in proximity to the neuronal soma. Furthermore, spine density patterns of basilar dendrites remain unchanged while the density of mature vs. immature spines significantly changes. These effects were not seen in the apical dendrites, indicating alcohol's influence on different neuronal parts in a single cell. In addition, these results suggest that the innervations of the soma and basilar dendrites by thalamic projections may play a role. Thus, our data demonstrates that postnatal exposure to alcohol produces changes in the neuronal organization of rat adolescent PFC that may affect the performance on prefrontal-dependant behavioral tasks.

Ethanol self-administration modulation of NMDA receptor subunit and related synaptic protein mRNA expression in prefrontal cortical fields in cynomolgus monkeys

BACKGROUND

Functional impairment of the orbital and medial prefrontal cortex underlies deficits in executive control that characterize addictive disorders, including alcohol addiction. Previous studies indicate that alcohol alters glutamate neurotransmission and one substrate of these effects may be through the reconfiguration of the subunits constituting ionotropic glutamate receptor (iGluR) complexes. Glutamatergic transmission is integral to cortico-cortical and cortico-subcortical communication, and alcohol-induced changes in the abundance of the receptor subunits and/or their splice variants may result in critical functional impairments of prefrontal cortex in the alcohol-addicted state.

METHODS AND RESULTS

The effects of chronic ethanol self-administration on glutamate receptor ionotropic NMDA (GRIN), as well as GRIN1 splice variant mRNA expression was studied in the orbitofrontal cortex (OFC; Area 13), dorsolateral prefrontal cortex (DLPFC; Area 46) and anterior cingulate cortex (ACC; Area 24) of male cynomolgus monkeys. Chronic ethanol self-administration resulted in significant changes in the expression of NMDA subunit mRNA expression in the DLPFC and OFC, but not the ACC. In DLPFC, the overall expression of NMDA subunits was significantly decreased in ethanol treated monkeys. Slight but significant changes were observed for synaptic associated protein 102 kD (SAP102) and neuronal nitric oxide synthase (nNOS) mRNAs. In OFC, the NMDAR1 variant GRIN1-1 was reduced while GRIN1-2 was increased. Furthermore, no significant changes in GFAP protein levels were observed in either the DLPFC or OFC.

CONCLUSION

Results from these studies provide the first demonstration of posttranscriptional regulation of iGluR subunits in the primate brain following long-term ethanol self-administration. Furthermore, changes in these transcripts do not appear to reflect changes in glial activation or loss. Further studies examining the expression and cellular localization of subunit proteins and receptor pharmacology would shed more light on the findings reported here.

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.

Proteomics approach in the study of the pathophysiology of alcohol-related brain damage

AIMS

Chronic, excessive drinking of alcohol can induce brain damage in the regions important for neurocognitive function. Some of the damage are permanent while some are appearantly reversible. It is our aim to understand the molecular mechanisms underlying alcohol-induced and/or related brain damage, particularly of that observed in 'medically uncomplicated' (without heptatic cirrhosis or Wernicke-Korsakoff Syndrome [WKS]) alcoholics.

METHODS

A high-throughput proteomics technology has been applied to several 'alcohol-sensitive' brain regions from uncomplicated and hepatic cirrhosis-complicated alcoholics to understand the mechanisms of alcohol-related brain damage at the level of protein expression.

RESULTS

It was clearly demonstrated that each brain region reacts in significantly different manner to chronic alcohol ingestion. Appearant abnormalities in vitamin B1 (thiamine)-related biochemical pathways were observed in several brain regions, such as the dorsolateral prefrontal cortex, genu (a frontal part of the corpus callosum) and cerebellar vermis in uncomplicated alcoholics, suggesting that the reduction of this important nutritional component might be associated with brain damage even without the signs of WKS. In addition, in the two different subregions of the corpus callosum (genu and splenium [a posterior part of the corpus callosum]) and the cerebellar vermis, significant differences in protein expression profiles between uncomplicated and complicated alcoholics with hepatic cirrhosis were identified, suggesting that hepatic factors such as ammonia have significant additive influences on brain protein expression, which might lead to the structural changes and/or damage in these brain regions. Furthermore, in the hippocampus, significant change of the level of glutamine synthetase expression was observed, suggesting once again the importance of ammonia as a cause of brain damage in this region.

CONCLUSIONS

Although our data did not show any evidence of "direct" alcohol effects to induce the alteration of protein expression in association with brain damage, high-throughput neuroproteomics approaches are proven to have a potential to dissect the mechanisms of complex brain disorders.

Alcohol enhances Abeta42-induced neuronal cell death through mitochondrial dysfunction

Mitochondrial dysfunction is a hallmark of beta-amyloid (Abeta)-induced neuronal toxicity in Alzheimer's disease (AD). Epidemiological studies have indicated that alcohol consumption plays a role in the development of AD. Here we show that alcohol exposure has a synergistic effect on Abeta-induced neuronal cell death. Abeta-treated cultured neurons displayed spontaneous generation of reactive oxygen species (ROS), disruption of their mitochondrial membrane potential, induction of caspase-3 and p53 activities, and loss of cell viability. Alcohol exposure facilitated Abeta-induced neuronal cell death. Our study shows that alcohol consumption enhances Abeta-induced neuronal cell death by increasing ROS and mitochondrial dysfunction.

Impact of alcohol abuse on protein expression of midkine and excitatory amino acid transporter 1 in the human prefrontal cortex

BACKGROUND

Alcoholism is associated with shrinkage of brain tissue and reduction in the number of neurons and dendritic arbors particularly in the prefrontal cortex. These changes correlate with the cognitive defects common in alcoholics. A recent study investigated the mRNA expression of selected genes in the prefrontal cortex and found that the levels of mRNA encoding the neurotrophic factor, midkine (MDK), and the excitatory amino acid transporter 1 (EAAT1) were significantly higher in alcoholics compared with nonalcoholic controls. This study aimed to investigate, whether the transcriptional changes observed result in alterations to protein expression. Additionally, the study aimed to expand our understanding of MDK and EAAT1 action by localizing their expression within morphologically and functionally distinct layers of this brain region.

METHODS

Quantitative changes in protein levels of MDK and EAAT1 were investigated in alcoholic and control cases using Western blots. Immunohistochemistry was utilized to localize proteins expression in formalin-fixed sagittal sections of the prefrontal cortex.

RESULTS

A marked increase was revealed in protein expression of both genes in the prefrontal cortex of chronic alcoholics. MDK-like immunofluorescence in alcoholic and control cases was present in nuclei throughout the prefrontal cortex and was particularly apparent in cell bodies of astrocytes in cortical layer II. Immunolabeling of the EAAT1 was densest in cortical layer II in control cases and induced in deeper layers in alcoholic cases.

CONCLUSION

Midkine promotes neuronal outgrowth and survival. The up-regulation of MDK protein expression may indicate the induction of reparative processes. The amino acid transporter is vital for the removal of glutamate from the synaptic cleft. At alcohol withdrawal, extracellular glutamate is thought to reach excitotoxic concentrations. Up-regulation of EAAT1 throughout the cortical layers may indicate an attempt to combat elevated glutamate concentrations. The predominant expression of the two proteins in layer II of the cortex implies a region-specific role of astrocytes.

Social cognition in alcoholism: a link to prefrontal cortex dysfunction?

AIMS

Alcoholism is associated with a range of cognitive deficits. These deficits might be explained by the 'frontal lobe hypothesis' which suggests a specific vulnerability of the prefrontal cortex (PFC) to the neurotoxic effects of alcohol. Social cognition is thought to be processed in the PFC, but so far only few studies have addressed the issue of social cognition deficits in alcoholism. This review aims to evaluate the deficits in social cognition in alcoholic patients. In addition an outline for future perspectives is given.

METHODS

Medline and Psyclit searches were performed for a 30-year period (1977-2007).

RESULTS

Alcoholism is associated clearly with social cognition impairments which include emotional face and prosody perception problems, theory of mind deficits and humour processing difficulties.

CONCLUSIONS

In summary, the social cognition impairments are consistent with the frontal lobe hypothesis of alcoholism. Future studies should focus on (i) the delineation of the basic cognitive processes which underlie social cognition deficits; and (ii) their relevance as predictors of treatment outcome in alcoholism.

Motor functioning and alcohol dependence

BACKGROUND

Autopsy and neuroimaging research in stably abstinent alcoholics illuminated structural and functional abnormalities in brain areas that organize and coordinate motor functioning. Researchers that used behavioural tasks to measure motor functioning found that abstinent alcoholics perform worse than healthy controls. These researchers however did not analyze timed responses into their cognitive and motor components. They thus were unable to decide which aspects of information processing are impaired. We here used a Fitts' task to examine differences in cognitive and motor components between abstinent alcoholics and healthy controls.

METHODS

Fifty-two abstinent alcoholics and 52 healthy controls participated in this research design. Fine motor functioning was assessed by means of the Fitts' task.

RESULTS

Abstinent alcoholics needed more time to perform timed responses than healthy controls. As both reaction and movement times were higher in abstinent alcoholics, both cognitive and motor processes seem to be impaired. When the task became more difficult (small targets instead of large targets) abstinent alcoholics needed proportionally more time to give the correct response than healthy controls. This phenomenon solely applied to movement times.

CONCLUSIONS

These research data indicate that abstinent alcoholics are somewhat impaired on a behavioral level. The execution of timed responses indeed was lengthier in abstinent alcoholics than in healthy controls. As both cognitive and motor processes were impaired, we here assume that both central and peripheral processes are affected by progressive alcohol intake. Abstinent alcoholics also have more difficulties to adapt their motor responses to changing task conditions.

The neurotoxicity of alcohol

Patterns of drinking are changing throughout the world and in many countries this will be detrimental to the health and welfare of the local population. Even uncomplicated alcoholics who have no specific neurological or hepatic problems show signs of regional brain damage and cognitive dysfunction. Many of these changes are exaggerated and other brain regions damaged in patients who have additional vitamin B1 (thiamine) deficiency (Wernicke-Korsakoff syndrome). Quantitative neuropathology techniques 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 provides fresh and frozen tissue for alcohol researchers. The tissues can be used to test hypotheses developed from structural neuropathological studies or from animal models and in vitro studies. Identification of reversible pathological changes and preventative medical approaches in alcoholism should enhance rehabilitation and treatment efforts, thereby mitigating debilitating morbidities and reducing mortality associated with this universal public health problem.

Current and future applications of magnetic resonance imaging and spectroscopy of the brain in hepatic encephalopathy

Hepatic encephalopathy (HE) is a common neuro-psychiatric abnormality, which complicates the course of patients with liver disease and results from hepatocellular failure and/or portosystemic shunting. The manifestations of HE are widely variable and involve a spectrum from mild subclinical disturbance to deep coma. Research interest has focused on the role of circulating gut-derived toxins, particularly ammonia, the development of brain swelling and changes in cerebral neurotransmitter systems that lead to global CNS depression and disordered function. Until recently the direct investigation of cerebral function has been difficult in man. However, new magnetic resonance imaging (MRI) techniques provide a non-invasive means of assessment of changes in brain volume (coregistered MRI) and impaired brain function (fMRI), while proton magnetic resonance spectroscopy (¹H MRS) detects changes in brain biochemistry, including direct measurement of cerebral osmolytes, such as myoinositol, glutamate and glutamine which govern processes intrinsic to cellular homeostasis, including the accumulation of intracellular water. The concentrations of these intracellular osmolytes alter with hyperammonaemia. MRS-detected metabolite abnormalities correlate with the severity of neuropsychiatric impairment and since MR spectra return towards normal after treatment, the technique may be of use in objective patient monitoring and in assessing the effectiveness of various treatment regimens.

Monitoring the effects of chronic alcohol consumption and abstinence on brain metabolism: a longitudinal proton magnetic resonance spectroscopy study

BACKGROUND

This study focused on metabolic brain alterations in recently detoxified alcohol-dependent patients (S1) and their possible reversibility after 3 (S2) and 6 months (S3) of abstinence.

METHODS

Thirty-three alcohol-dependent patients and 30 healthy control subjects were studied with multislice proton magnetic resonance spectroscopic imaging (echo time = 135 msec at 1.5 T at three time points).

RESULTS

In the patient group, we found that choline-containing compounds (Ch) in three frontal and cerebellar subregions at S1 were significantly below normal, whereas N-acetyl aspartate (NAA) differences did not reach significance but showed a trend toward below-normal values in frontal white matter. Abstinent patients showed a significant increase of Ch in all subregions at S2. At S3, no further significant metabolite changes in abstinent patients compared with S2 could be detected. No significant increase of NAA could be detected at follow-up.

CONCLUSIONS

The increase of the Ch signal in the follow-up measurement after 3 months in abstinent alcohol-dependent patients supports the hypotheses of an alcohol- or alcohol detoxification-induced altered cerebral metabolism of lipids in membranes or myelin, which seems to be reversible with duration of alcohol abstinence.

Striatal dopamine D1 receptors in type 1 and 2 alcoholics measured with human whole hemisphere autoradiography

A considerable number of human and animal studies have implied the importance of dopamine system and alterations in dopamine receptors in the context of alcoholism. However, it has remained unclear if the alcohol-abuse related dopaminergic deficit is specifically associated with certain receptor subtype. The aim of this study was to compare putative alterations of dopamine D(1) receptors in caudate and putamen of nine type 1 alcoholics, eight type 2 alcoholics and 10 healthy controls by using [(3)H]SCH 23390 as a radioligand in postmortem human whole hemisphere autoradiography. In addition, we compared the present results to our earlier studies on dopamine transporters and dopamine D(2) receptors in these same subjects and evaluated the putative correlations of dopamine D(1) receptor densities between the nucleus accumbens and the above-mentioned structures. Our results show that alcoholics do not have significantly different striatal dopamine D(1) receptor densities compared to controls. Neither were there any significant correlations between the dopamine D(1) receptors and the two other dopamine binding sites. However, the correlations of the dopamine D(1) receptors between nucleus accumbens and dorsal striatal structures were consistently and mostly statistically significantly positive in alcoholics, but not in controls, which may suggest some pathology related to addiction. In addition, considering the facts that dopamine D(1) receptors were more abundant in the mesolimbic nucleus accumbens than in the caudate or putamen and that there was a strong tendency towards lower binding among type 1 alcoholics may suggest the importance of dopamine D(1) receptors in reward and/or alcoholism.

Dopamine and alcoholism: neurobiological basis of ethanol abuse

The role of the dopamine (DA) system in brain reward mechanisms and the development of substance abuse has been well established. We review earlier animal and human studies on DA and alcoholism with some relevant issues relating to those studies. The present animal and human data suggest several alterations in the DA system in the context of alcoholism. Receptor studies imply that DA D(2) receptor density and function are lower at least among type 1 alcoholics, which suggests that they could benefit from drugs that enhance DAergic activity, such as partial DA agonists. These drugs could help to restore suboptimal levels of DAergic activity by reducing both the craving for alcohol in abstinence and the euphoria subsequent to alcohol's release of DA in the nucleus accumbens (NAC), thus providing negative reinforcement for relapse.

Myelinated nerve fibres in the subcortical white matter of cerebral hemispheres are preserved in alcoholic subjects

Previous studies have found that the primary change in the brain of chronic alcoholics is a selective loss of white matter in cerebral hemispheres. It is unknown whether the loss of white matter is due to alcohol-induced degeneration of axons in white matter, and this hypothesis has never been tested. We used a newly developed stereological method to investigate whether the length and diameter of myelinated fibres change in the subcortical white matter of male alcoholic subjects. We found no significant differences between control and alcoholic subjects with respect to the total volume, total length, and mean diameter of myelinated fibres in white matter. Our results do not find any support for the hypothesis that chronic alcoholic subjects may suffer from a degeneration of axons (myelinated fibres) in white matter in cerebral hemispheres.

Direct recording of the output of the motor cortex produced by transcranial magnetic stimulation in a patient with cerebral cortex atrophy

OBJECTIVE

To examine the descending motor activity evoked by transcranial magnetic stimulation (TMS) in a chronic alcoholic patient with a slight atrophy of the peri-central cortex and compare with that observed in neurologically intact subjects.

METHODS

EMGs from the first dorsal interosseous (FDI) muscle, and descending activity from an electrode implanted in the high cervical epidural space for relief of pain were recorded after TMS of the hand area of motor cortex. A figure-of-8 coil was used to induce either a posterior-anterior (PA) or a latero-medial (LM) flow across the central sulcus.

RESULTS

In intact subjects, LM stimulation evoked the earliest volley, which we termed a D wave. This was followed by later, presumed I waves at intervals of about 1.5 ms. At a stimulus intensity of 120% resting threshold (RMT), up to 5 I waves were seen. PA stimulation rarely evoked D waves at intensities up to 120% RMT, but 3 or 4 I waves were visible in all subjects. The patient had an increased resting threshold, and the descending volleys were dominated by a D wave. I waves were unclear, with two possible small peaks at 5.5 and 7.2 ms.

CONCLUSIONS

The lack of I waves in the patient was probably due to an impairment of interneuronal circuitry in the context of the brain damage related to chronic alcohol abuse, and is consistent with a trans-synaptic origin of the I waves in humans. The intact D wave is consistent with the assumption that the D wave represents direct stimulation of the axons of intact corticospinal neurones in the subcortical white matter. The patient's increased RMT reflects the fact that usually multiple descending volleys are needed to discharge resting spinal motoneurones.

Neuropathological alterations in alcoholic brains. Studies arising from the New South Wales Tissue Resource Centre

Alcohol dependence and abuse are among the most costly health problems in the world from both social and economic points of view. Patterns of drinking appear to be changing throughout the world with more women and young people drinking heavily. Excessive drinking can lead to impairment of cognitive function and structural brain changes--some permanent, some reversible. Patterns of damage appear to relate to lifetime alcohol consumption but, more importantly, to associated medical complications. The most significant of these is the alcohol-related vitamin deficient state, the Wernicke-Korsakoff syndrome (WKS), which is caused by thiamin deficiency but is seen most commonly in alcoholics. Careful selection and classification of alcoholic cases into those with and without these complications, together with detailed quantitative neuropathological analyses has provided data that gives clues to the most vulnerable regions and cells in the brain. Brain shrinkage is largely accounted for by loss of white matter. Some of this damage appears to be reversible. Alcohol-related neuronal loss has been documented in specific regions of the cerebral cortex (superior frontal association cortex), hypothalamus and cerebellum. No change is found in basal ganglia, nucleus basalis, or serotonergic raphe nuclei. Many of these regions which are normal in uncomplicated alcoholics are damaged in those with the WKS. Dendritic and synaptic changes have been documented in alcoholics and these, together with receptor and transmitter changes, may explain functional changes and cognitive deficits, which precede more severe structural neuronal changes. A resource to provide human brain tissues for these types of studies has been developed at the University of Sydney--the New South Wales Tissue Resource Centre. The aim of this facility is to provide research groups throughout the world with fresh and/or frozen tissues from well-characterized cases of alcohol-related brain damage and matched controls. The development of new technologies in pathology and molecular biology means that many more questions can be addressed using appropriately stored human brain tissues. Examples of the application of some of these techniques, involving neurochemical, neuropharmacological, neuroimaging and gene expression studies are included in this paper. Important public health outcomes have arisen from some of these studies including the enrichment of bread flour with thiamin for the whole of Australia. Researchers with an interest in alcohol studies can access tissues from this brain bank.