By contrast, upwards of 2 million alcoholics develop permanent and debilitating conditions that require lifetime custodial care (Oscar-Berman and Evert 1997; Rourke and Løberg 1996). However, most problem drinkers have mild neuropsychological difficulties, which improve within a year of abstinence (Bartsch et al. 2007; Ende et al. 2005; Fein et al. 2006b). The present study was a cross-sectional design; therefore, it is unknown whether the functional connectivity abnormalities in the AUD group are a result of heavy drinking or a predisposition toward AUD. Although the average LOS within the AUD group was long (5.2 +/−7.2 years), we chose a wide range of abstinence by design to generalize our findings to the larger population of AUD men and women in our catchment area. However, we performed additional analyses that clearly indicated a correlation between LOS and connectivity patterns that were identified to be different between the AUD and CTRL groups.
- Chronic and excessive alcohol consumption is a significant public health problem in the USA and among the leading causes of onset of cognitive impairment and dementia.
- To complicate matters, Volkow et al. (1992) found that the right frontal cortex showed greater hypometabolism than the left, and the left parietal cortex showed greater hypometabolism than the right.
- Histopathology showed that treatment with rasagiline reduced the lesions in thalamus and colliculi observed in the thiamine-deficient brain (Eliash et al. 2009).
- If the cerebellum is less sensitive to alcohol during this period, this could account for the developmental difference in sensitivity to alcohol.
Structural MRI Findings in Alcoholism-Related Brain Diseases
Parsons (1994) reported that although alcoholic men and women showed impaired performance on neuropsychological tests relative to same-sex nonalcoholic control participants, only the alcoholic men differed from their controls on a measure of visually evoked event-related brain potentials. Other investigators found that alcoholic men and women displayed similar electrophysiological abnormalities (Hill and Steinhauer 1993). After correction for multiple comparisons, the cerebellar cortex and somatosensory cortex each approached having a significant age × sex × treatment × time interaction. Interestingly, adult males showed alcohol effects on both of these regions despite showing no overall effects on whole brain volume.
MRI Data Acquisition
Ultimately, research on these phenotypes and their underlying genetic variation is directly relevant for the development of new medications and models to guide the matching of medications with individuals most likely to benefit from them. Perhaps the most consistent evidence of greater RH dysfunction has come from studies utilizing electrophysiological measures, although this observation has to be tempered by the poor spatial resolution of ERPs. In one study, ERP abnormalities in alcoholics were particularly evident in the right frontal area (Porjesz and Begleiter 1982). In addition, the alcoholics did not show normal asymmetrical ERP responses (i.e., the finding that RH amplitudes are normally greater than LH amplitudes; see also Zhang et al. 1997).
These data indicated that alcohol’s sensory properties (a CS that predicts intoxication) were related to DA release, although DA and BAC were uncorrelated in time, again suggesting that striatal DA transmission is not a response to intoxication, per se. This idea is consistent with electrophysiological studies in animals that have shown an initial response of midbrain DA neurons to a reinforcer, but a shift of the DA response toward a predictive stimulus (CS) possessing a learned association with the reward. After the CS, DA neurons then signal unexpected outcomes by either increasing (unexpected reward following a CS indicating no reinforcement) or decreasing (unexpected reward absence) their firing rates (Schultz et al., 1997). In fact, data using the RAC PET technique with alcohol cues support the importance of the learned contingency and reward outcome (Yoder et al., 2009). In particular, alcohol’s visual and olfactory cues, which subjects were told would herald imminent intoxication from intravenous alcohol, resulted in decreased striatal DA transmission when alcohol was withheld; nonalcohol cues (which subjects understood would predict saline infusion) increased DA transmission during unexpected alcohol infusion. Elsewhere, IV-EtOH alone (dissociating drug action from its gustatory and olfactory qualities) has not reliably increased DA in humans (Yoder et al., 2005; but for other reasons why a response to alcohol itself could and does occur see also Yoder et al., 2007; Ramchandani et al., 2011).
- The authors thank all MOB lab members and collaborators who have been involved in any aspect of design, recruitment, assessment, data analyses, editing, or neuroimaging for this study.
- For these experiments, Acheson and colleagues (1999) administered alcohol to adolescent and adult rats for 5 days, then injected the animals with a chemical that induces seizures and rated the severity and duration of the seizures.
- Other cognitive, behavioral, and affective consequences have been reported after AIE, including impaired performance of executive functions, memory impairment, reduced cognitive flexibility, greater risk preference and disinhibition, and elevated social (and sometimes general) anxiety.
- In two recent studies (Dirksen et al. 2006; Oscar-Berman et al. 2004), we administered a series of neuropsychological tasks sensitive to dysfunction of frontal brain systems to abstinent alcoholics, including groups of patients with Korsakoff’s syndrome.
DTI Findings in Animal Models of Uncomplicated Alcoholism
As compared to working memory, less research has been conducted on alcohol’s effects on neural correlates of verbal learning (i.e., the process of acquiring, retaining, and recalling of verbal material). Heavy drinking adolescents (ages 16-18) displayed significantly increased amplitudes of a recollection-related ERP component (P540, predominately left parietal), and more forgetting after a delay, as compared to substance naïve controls with similar recognition performance on a modified version of the Rey Auditory Verbal Learning Test (Smith et al., 2017). Interestingly, adolescents who engaged in binge drinking and marijuana use evinced similar encoding-related BOLD responses to controls in frontal regions, whereas binge-drinking-only adolescents showed greater frontal BOLD response than controls, with similar task performance observed across all groups (Schweinsburg, Schweinsburg, Nagel, Eyler, & Tapert, 2011).
Alcohol’s Effects on the Adolescent Brain
Alcoholics, however, showed the exact opposite pattern, and the degree to which this modulation was deviant to that of controls was predicted by the amount of lifetime alcohol consumption. Thus, the observed brain activity differences can be explained, at least in part, by past heavy drinking and may include conditions mitigating lifetime alcohol consumption, some of which possibly predating the onset of alcoholism. Human studies offer a full depiction of the consequences of chronic alcohol exposure but are limited by ethical considerations.
DTI Findings in Uncomplicated Alcoholism
This technique allows identifying clusters of connections that show similar patterns of temporal functional variation in their functional connectivity over time. The present study was designed to test the hypothesis that sex and age are critical factors in influencing the brain’s response to binge EtOH exposure. Further, we hypothesised that stronger effects would be observed in the developing brain, with female mice at greater risk than male mice. Indeed, age and sex interacted with EtOH to influence whole‐brain volumes across time, suggesting that both factors influence the brain’s response to binge EtOH. Analysing the effects within groups revealed treatment × time interactions in adolescent females with EtOH resulting in decreased brain growth at both the post‐treatment and recovery timepoints. Whilst adolescent males showed a similar pattern, the treatment × time interaction failed to reach significance in this group, and adolescent females showed an effect size almost double than that of adolescent males (0.174 vs 0.08).
Although the number of neurons and neuronal connections in the prefrontal cortex appear to decline during adolescence, the relative importance of the frontal lobes increases. KS patients show FA deficits in the fornix (Nahum et al., 2015), Papez and medial limbic circuits compared to alcoholics without KS (Segobin et al., 2015). HE patients have MD elevations in corpus callosum, internal capsule, frontal white matter (Kale et al., 2006), and occipital white matter (R. Kumar et al., 2008). CPM patients show elevated MD in middle cerebellar peduncles (Min, Park, & Hwang, 2012; Nair, Ramli, Rahmat, & Mei-Ling, 2012). These findings suggest that low NAA levels initially observed in recently sober alcoholics reflect neurodegeneration without cell death, and increases with abstinence may reflect healing without cell generation.
Hepatic Encephalopathy (HE) is believed to arise from high levels of ammonia circulating in the blood stream, occurring during acute or chronic liver disease, often as a consequence of alcoholism. Altered ammonia levels in the body directly influence brain metabolism and can lead to glial swelling and neuronal cell death (Kundra, Jain, Banga, Bajaj, & Kar, 2005; Rama Rao & Norenberg, 2014). HE patients may appear confused, disoriented, and have poor coordination (Prakash & Mullen, 2010; Vaquero, Chung, Cahill, & Blei, 2003). MRI images show bilateral, symmetrical high-intensity signals in the basal ganglia, prominent in globus pallidus, and substantia nigra (Figure 1C) (Binesh et al., 2006; Cordoba, Sanpedro, Alonso, & Rovira, 2002; Naegele et al., 2000), as well as along the cortico-spinal tract and white-matter of the cerebral hemispheres (Rovira et al., 2002). (A) Brain scan of an alcoholic man with Wernicke’s encephalopathy showing the typical hypertensities in the mammilary bodies and colliculi (reprint with permission from (Sullivan & Zahr, 2008)).
Although it is beyond the scope of this article to review the changes occurring in various brain structures and neurotransmitter systems in more detail, this brief description demonstrates that adolescence is a period of profound alterations in brain function. Therefore, it is reasonable to expect that alcohol’s effects on the brain and behavior may differ for adolescents and adults. The following sections will review some of the differences in sensitivity to alcohol that have been identified using animal models. In vivo imaging studies in humans and animal models will continue to provide an evolving picture of the course of alcoholic brain disease through remissions and exacerbations as long-term studies follow human alcoholics as they age and as new initiatives evaluate adolescents before they are exposed to alcohol. Short-term (6 weeks) abstinence seems sufficient to observe some brain-volume recovery but does not result in equivalent brain volumes between recovering chronic alcoholics and healthy controls (Mann et al. 2005). That is, older alcoholics exhibit reduced capacity for recovery compared with younger alcoholics (Fein et al. 1990; Munro et al. 2000; Reed et al. 1992; Rourke and Grant 1999).
How Acute and Chronic Alcohol Consumption Affects Brain Networks: Insights from Multimodal Neuroimaging
Widespread anatomical connections of the ACC with lateral prefrontal cortex, motor cortex, spinal cord, and limbic structures make the ACC suitable for its multifaceted role in self-regulation (Devinsky et al., 1995). Neuroimaging studies of acute alcohol effects on cognitive control are scant (Gundersen et al., 2008; Paulus et al., 2006). 1 (Marinkovic et al., 2011), show that acute moderate intoxication (0.6 g/kg EtOH for men, 0.55 g/kg for women) selectively attenuates the ACC activity during both high-conflict trials and erroneous responses across different inhibitory tasks, indicating the vulnerability of the top-down control to intoxication (Ridderinkhof et al., 2002). Even though caution is warranted in interpreting fMRI-BOLD magnitude changes because of alcohol’s vasoactive properties (Rickenbacher et al., 2011), this effect alcohols effects on the brain: neuroimaging results in humans and animal models pmc persists when alcohol-induced changes in cerebral perfusion are taken into account. To assess age-dependent effects of alcohol, Markwiese and colleagues (1998) compared the performance of alcohol-exposed adolescent and adult rats in the Morris water maze task.
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