The effects of alcohol intoxication on neuronal activation at different levels of cognitive load

Effects of acute alcohol administration on working memory: a systematic review and meta-analysis

RATIONALE

Alcohol-induced executive function deficits may underlie associations between alcohol, self-regulation, and hazardous behaviors. Studies examining the effects of alcohol administration on working memory, an important executive functioning component, have produced mixed findings. Acute alcohol effects on working memory remain unclear.

OBJECTIVES

We aimed to conduct a systematic review and meta-analysis on the effects of acute alcohol administration on working memory outcomes in studies of healthy adults.

METHODS

We performed a systematic search of PubMed, MEDLINE, and PsycINFO from inception to June 2021. Studies were included if they met criteria, including healthy participants and administration of quantified alcohol doses against comparative controls. Data extracted included primary working memory outcomes, alcohol doses, and study characteristics. Study quality was assessed using an established validity measure. Working memory task type, alcohol dose, control condition type, and sex/gender composition were explored as moderators using mixed-effects models and meta-regressions.

RESULTS

Thirty-two studies (1629 participants) provided sufficient data for 54 comparisons between alcohol and control conditions. Random-effects meta-analysis indicated that alcohol administration produced significant, small- to medium-sized working memory decrements (g [95% CI] =  - 0.300 [- 0.390 to - 0.211], p < 0.001). Moderation analyses suggested that these effects differed as a function of task type, dose, control condition type, and sex/gender composition. The average quality rating across studies was good.

CONCLUSIONS

Alcohol administration significantly impaired working memory performance, particularly when executive-related manipulation processes were involved. Future research is needed to investigate how alcohol-induced working memory impairments relate to compromised self-regulation, hazardous behavior, and negative drinking consequences.

Effects of Mixing Energy Drinks With Alcohol on Driving-Related Skills

BACKGROUND

Energy drinks (EDs) reduce sleepiness and fatigue and improve driving performance whereas alcohol does just the opposite. Although it is a trendy combination among young people, the effects of alcohol mixed with EDs on driving performance have been poorly studied. The aim was to assess if there is an interaction between the effects of both drinks on driving-related skills as well as perceptions about driving ability.

METHODS

We conducted a randomized, double-blind, and placebo-controlled 4-way crossover clinical trial. Participants were 16 healthy volunteers. Interventions of 60 g of ethanol and 750 mL of Red Bull (RB) were administered in 2 separated doses. Conditions were alcohol + RB placebo, alcohol + RB, alcohol placebo + RB, and both placebos. Objective performance was assessed using a tracking test and simple reaction time, N-Back, and movement estimation tasks. Additionally, willingness to drive, other subjective effects, and ethanol and caffeine blood concentrations were also measured.

RESULTS

Alcohol increased the time outside the road in the tracking test and increased simple reaction time, but the addition of RB had no main or interaction effects on performance. Nonetheless, driving-related skills after alcohol + RB were better than after alcohol alone. Willingness to drive increased with the combination of drinks. RB also reduced alcohol-induced sedation whereas drunkenness did not change. These effects were seen even though alcohol + RB increased alcohol (14.8%) and caffeine plasma concentrations (17.6%).

CONCLUSIONS

Mixing EDs with alcohol predisposes consumers to drive under alcohol influence, perhaps in part because EDs counteract its detrimental effects on driving-related skills. Clinicaltrials.gov: NCT02771587.

Acute effects of alcohol on resting-state functional connectivity in healthy young men

Alcohol abuse and dependence remain significant public health issues, and yet the brain circuits that are involved in the rewarding effects of alcohol are poorly understood. One promising way to study the effects of alcohol on neural activity is to examine its effects on functional connectivity between brain areas involved in reward and other functions. Here, we compared the effects of two doses of alcohol (0.4 and 0.8 g/kg) to placebo on resting-state functional connectivity in brain circuits related to reward in 19 healthy young men without histories of alcohol problems. The higher, but not the lower, dose of alcohol, significantly increased connectivity from reward-related regions to sensory and motor cortex, and between seeds associated with cognitive control. Contrary to expectation, alcohol did not significantly change connectivity for the ventral striatum at either dose. These findings reveal unrecognized effects of alcohol on connectivity from reward-related regions to visual and sensory cortical areas.

Association between free-living sleep and memory and attention in healthy adolescents

In laboratory studies, imposed sleep restriction consistently reduces cognitive performance. However, the association between objectively measured, free-living sleep and cognitive function has not been studied in older adolescents. To address this gap, we measured one week of sleep with a wrist-worn GT3X+ actigraph in 160 adolescents (96 girls, 17.7 ± 0.3 years) followed by assessment of working memory with an n-back task and visual attention with a Posner cue-target task. Over the week, participants spent 7.1 ± 0.8 h/night in bed and slept 6.2 ± 0.8 h/night with 88.5 ± 4.8% efficiency and considerable intra-participant night-to-night variation, with a standard deviation in sleep duration of 1.2 ± 0.7 h. Sleep measures the night before cognitive testing were similar to weekly averages. Time in bed the night before cognitive testing was negatively associated with response times during the most challenging memory task (3-back; p = 0.005). However, sleep measures the night before did not correlate with performance on the attention task and weekly sleep parameters were not associated with either cognitive task. Our data suggests shorter acute free-living sleep may negatively impact difficult memory tasks, however the relationship between free-living sleep and cognitive task performance in healthy adolescents is less clear than that of laboratory findings, perhaps due to high night-to-night sleep variation.

Resting state functional connectivity of the amygdala and problem drinking in non-dependent alcohol drinkers

Alcohol misuse is associated with dysfunction of the amygdala-prefrontal cortical circuit. The amygdala and its cortical targets show decreased activity during a variety of task challenges in individuals engaged in problem drinking. On the other hand, it is less clear how amygdala resting state functional connectivity (rsFC) may be altered in association with alcohol misuse and whether such changes are restricted to prefrontal cortical structures. Further, the influences of comorbid substance use and depression and potential sex differences have not been assessed in earlier work. Here, with fMRI data from a Nathan Kline Institute/Rockland sample of 83 non-dependent alcohol drinkers (26 men), we addressed changes in whole brain rsFC of the amygdala in association with problem drinking as indexed by an alcohol involvement score. Imaging data were processed with Statistical Parametric Mapping following standard routines and all results were examined at voxel p < 0.001 uncorrected in combination with cluster p < 0.05 corrected for false discovery rate. Alcohol misuse was correlated with decreased amygdala connectivity with the dorsal anterior cingulate cortex (dACC) irrespective of depression and other substance use. Changes in amygdala-dACC connectivity manifested in the latero-basal subdivision of the amygdala. Further, men as compared to women showed a significantly stronger relationship in decreased amygdala-dACC connectivity and problem drinking, although it should be noted that men also showed a trend toward higher alcohol involvement score than women. The findings add to a growing literature documenting disrupted amygdala-prefrontal cortical functions in relation to alcohol misuse.

Pharmacological and Expectancy Effects of a Low Amount of Alcohol Drinking on Outcome Valuation and Risk Perception in Males and Females

The high-dose, alcohol-induced influences on risk perception and loss aversion depend on sex. On the other hand, low-dose alcohol has less effect on risky behavior. However, the effect of low-dose alcohol on subjective valuation of gain or loss and also the effect of placebo (expectancy of alcohol) on risk perception have not been fully investigated. We investigated the effects of low-dose alcohol (0.02 g/100 ml blood alcohol concentration) and placebo effects on subjective risk perception and subjective valuation of uncertain gain and loss in females and males. Participants in the control group and the placebo group were served alcohol-free, wine-flavored beverage and participants of alcohol group were served wine (14% alcohol). The placebo group was not informed that the drink was not alcohol but the control group was informed. Then paper-pencil tasks for subjective risk perception and valuation of gain or loss were performed 45 min after drinking the beverage. The participants were asked to draw the line on a 180 mm scale for each question. The placebo effects as well as the low-dose alcohol effects were observed in subjective valuations of gain or loss. Except for effect of beverages, a gender difference was also observed for subjective likelihood. The females estimated a low-probability loss as more likely and estimated a high-probability gain as less likely than did the males. From the Stevens' law fitting analysis, the placebo, not alcohol, significantly induced the psychophysical effect of the subjective valuation of gain or loss. These results indicate that the psychological effects of expectancy of alcohol (placebo) could be a major factor in changing the subjective valuation of gain or loss over the pharmacological effects of a small amount of alcohol (like a glass of wine). Furthermore, these results also indicate that gender differences should be taken into account when investigating pharmacological or psychological effect on decision-making.

Alcohol Hits You When It Is Hard: Intoxication, Task Difficulty, and Theta Brain Oscillations

Background

Alcohol intoxication is known to impair decision making in a variety of situations. Previous neuroimaging evidence suggests that the neurofunctional system subserving controlled processing is especially vulnerable to alcohol in conflict‐evoking tasks. The present study investigated the effects of moderate alcohol intoxication on the spatiotemporal neural dynamics of event‐related total theta (4 to 7 Hz) power as a function of task difficulty.

Methods

Two variants of the Simon task manipulated incongruity via simple spatial stimulus‐response mismatch and, in a more difficult version, by combining spatial and semantic interference. Healthy social drinkers participated in both alcohol (0.6 g/kg ethanol for men, 0.55 g/kg for women) and placebo conditions in a counterbalanced design. Whole‐head magnetoencephalography (MEG) signals were acquired and event‐related total theta power was calculated on each trial with Morlet wavelets. MEG sources were estimated using anatomically constrained, noise‐normalized, spectral dynamic statistical parametric mapping.

Results

Longer reaction times and lower accuracy confirmed the difficulty manipulation. Response conflict (incongruity) increased and alcohol intoxication decreased event‐related theta power overall during both tasks bilaterally in the medial and ventrolateral prefrontal cortices. However, alcohol‐induced theta suppression was selective for conflict only in the more difficult task which engaged the dorsal anterior cingulate (dAC) and anterior inferolateral prefrontal cortices. Theta power correlated negatively with drinking levels and disinhibition, suggesting that cognitive control is susceptible in more impulsive individuals with higher alcohol intake.

Conclusions

The spatiotemporal theta profile across the 2 tasks supports the concept of a rostrocaudal activity gradient in the medial prefrontal cortex that is modulated by task difficulty, with the dAC as the key node in the network subserving cognitive control. Conflict‐related theta power was selectively reduced by alcohol only under the more difficult task which is indicative of the alcohol‐induced impairment of conflict monitoring and top‐down regulation. Compromised executive control under alcohol may underlie a range of adverse effects including reduced competency in conflict‐inducing or complex situations.

On the existence of a generalized non-specific task-dependent network

In this paper we suggest the existence of a generalized task-related cortical network that is up-regulated whenever the task to be performed requires the allocation of generalized non-specific cognitive resources, independent of the specifics of the task to be performed. We have labeled this general purpose network, the extrinsic mode network (EMN) as complementary to the default mode network (DMN), such that the EMN is down-regulated during periods of task-absence, when the DMN is up-regulated, and vice versa. We conceptualize the EMN as a cortical network for extrinsic neuronal activity, similar to the DMN as being a cortical network for intrinsic neuronal activity. The EMN has essentially a fronto-temporo-parietal spatial distribution, including the inferior and middle frontal gyri, inferior parietal lobule, supplementary motor area, inferior temporal gyrus. We hypothesize that this network is always active regardless of the cognitive task being performed. We further suggest that failure of network up- and down-regulation dynamics may provide neuronal underpinnings for cognitive impairments seen in many mental disorders, such as, e.g., schizophrenia. We start by describing a common observation in functional imaging, the close overlap in fronto-parietal activations in healthy individuals to tasks that denote very different cognitive processes. We now suggest that this is because the brain utilizes the EMN network as a generalized response to tasks that exceeds a cognitive demand threshold and/or requires the processing of novel information. We further discuss how the EMN is related to the DMN, and how a network for extrinsic activity is related to a network for intrinsic activity. Finally, we discuss whether the EMN and DMN networks interact in a common single brain system, rather than being two separate and independent brain systems.

The effects of acute alcohol administration on the human brain: insights from neuroimaging

Over the last quarter century, researchers have peered into the living human brain to develop and refine mechanistic accounts of alcohol-induced behavior, as well as neurobiological mechanisms for development and maintenance of addiction. These in vivo neuroimaging studies generally show that acute alcohol administration affects brain structures implicated in motivation and behavior control, and that chronic intoxication is correlated with structural and functional abnormalities in these same structures, where some elements of these decrements normalize with extended sobriety. In this review, we will summarize recent findings about acute human brain responses to alcohol using neuroimaging techniques, and how they might explain behavioral effects of alcohol intoxication. We then briefly address how chronic alcohol intoxication (as inferred from cross-sectional differences between various drinking populations and controls) may yield individual brain differences between drinking subjects that may confound interpretation of acute alcohol administration effects. This article is part of the Special Issue Section entitled 'Neuroimaging in Neuropharmacology'.

Acute alcohol effects on attentional bias are mediated by subcortical areas associated with arousal and salience attribution

Acute alcohol ingestion increases attentional bias to alcohol-related stimuli; however, the underlying cognitive and brain mechanisms remain unknown. We combined functional magnetic resonance imaging (fMRI) with performance of a dual task that probed attentional distraction by alcohol-related stimuli during 'conflict' processing: the Concurrent Flanker/Alcohol-Attentional bias task (CFAAT). In this task, an Eriksen Flanker task is superimposed on task-unrelated background pictures with alcohol-associated or neutral content. Participants respond to the direction of a central 'target' arrow and ignore adjacent congruent (low cognitive load) or incongruent (high cognitive load) 'flanking' arrows. Using a between-subject design, 40 healthy moderate-to-heavy social drinkers received either no alcohol (placebo), 0.4 g/kg (low dose), or 0.8 g/kg (high dose) of alcohol, and underwent fMRI while performing the CFAAT. The low alcohol dose, relative to placebo, increased response latencies on trials with alcohol-associated backgrounds and, under low cognitive load, increased the activity evoked by these pictures within a medial hypothalamic region. Under high cognitive load, the low alcohol dose, relative to placebo, elicited greater activity within a more lateral hypothalamic region, and reduced activity within frontal motor areas. The high alcohol dose, relative to placebo, did not reliably affect response latencies or neural responses to background images, but reduced overall accuracy under high cognitive load. This effect correlated with changes in reactivity within medial and dorsal prefrontal cortices. These data suggest that alcohol at a low dose primes attentional bias to alcohol-associated stimuli, an effect mediated by activation of subcortical hypothalamic areas implicated in arousal and salience attribution.

Brain modifications after acute alcohol consumption analyzed by resting state fMRI

Resting-state functional magnetic resonance imaging (fMRI) is a recent breakthrough in neuroimaging research able to describe "in vivo" the spontaneous baseline neuronal activity characterized by blood oxygen level dependent (BOLD) signal fluctuations at slow frequency (0.01-0.1Hz) that, in the absence of any task, forms spatially distributed functional connectivity networks, called resting state networks (RSNs). The aim of this study was to investigate, in the young and healthy population, the changing of the RSNs after acute ingestion of an alcohol dose able to determine a blood concentration (0.5g/L) that barely exceeds the legal limits for driving in the majority of European Countries. Fifteen healthy volunteers underwent two fMRI sessions using a 1.5T MR scanner before and after alcohol oral consumption. The main sequence acquired was EPI 2D BOLD, one per each session. To prevent the excessive alcohol consumption the subjects underwent the estimation of blood rate by breath test and after the stabilization of blood alcohol level (BAL) at 0.5g/L the subjects underwent the second fMRI session. Functional data elaboration was carried out using the probabilistic independent component analysis (PICA). Spatial maps so obtained were further organized, with MELODIC multisession temporal concatenation FSL option, in a cluster representing the group of pre-alcohol sessions and the group of post-alcohol sessions, followed by the dual regression approach in order to evaluate the increase or decrease in terms of connectivity in the RSNs between the two sessions at group level. The results we obtained reveal that acute consumption of alcohol reduces in a significant way the BOLD signal fluctuations in the resting brain selectively in the sub-callosal cortex (SCC), in left temporal fusiform cortex (TFC) and left inferior temporal gyrus (ITG), which are cognitive regions known to be part of the reward brain network and the ventral visual system.

Striatocortical pathway dysfunction in addiction and obesity: differences and similarities

Neuroimaging techniques are starting to reveal significant overlap in the brain circuitry underlying addiction and disorders of dyscontrol over rewarding behaviors (such as binge eating disorder and obesity). Positron emission tomography (PET) has demonstrated impaired striatal dopamine (DA) signaling (decreased D2 receptors) in drug addiction and obesity that is associated with reduced baseline glucose metabolism in medial and ventral prefrontal brain regions. Functional magnetic resonance imaging (fMRI) has documented brain activation abnormalities that also implicate DA-modulated striato-cortical pathways. In this review we map findings from recent neuroimaging studies that differentiate brain activation in drug/food addiction from those in controls within brain networks functionally connected with ventral and dorsal striatum. We show that regions found to be abnormal in addiction and obesity frequently emerge at the overlap of the dorsal and the ventral striatal networks. Medial temporal and superior frontal regions functionally connected with dorsal striatum display greater vulnerability in obesity and eating disorders than in drug addictions, indicating more widespread abnormalities for obesity and eating disorders than for addictions. This corroborates involvement of both ventral striatal (predominantly associated with reward and motivation) and dorsal striatal networks (associated with habits or stimulus response learning) in addiction and obesity but also identify distinct patterns between these two disorders.

How acute and chronic alcohol consumption affects brain networks: insights from multimodal neuroimaging

BACKGROUND

Multimodal imaging combining 2 or more techniques is becoming increasingly important because no single imaging approach has the capacity to elucidate all clinically relevant characteristics of a network.

METHODS

This review highlights recent advances in multimodal neuroimaging (i.e., combined use and interpretation of data collected through magnetic resonance imaging [MRI], functional MRI, diffusion tensor imaging, positron emission tomography, magnetoencephalography, MR perfusion, and MR spectroscopy methods) that leads to a more comprehensive understanding of how acute and chronic alcohol consumption affect neural networks underlying cognition, emotion, reward processing, and drinking behavior.

RESULTS

Several innovative investigators have started utilizing multiple imaging approaches within the same individual to better understand how alcohol influences brain systems, both during intoxication and after years of chronic heavy use.

CONCLUSIONS

Their findings can help identify mechanism-based therapeutic and pharmacological treatment options, and they may increase the efficacy and cost effectiveness of such treatments by predicting those at greatest risk for relapse.

Biomechanical correlates of symptomatic and asymptomatic neurophysiological impairment in high school football

Concussion is a growing public health issue in the United States, and chronic traumatic encephalopathy (CTE) is the chief long-term concern linked to repeated concussions. Recently, attention has shifted toward subconcussive blows and the role they may play in the development of CTE. We recruited a cohort of high school football players for two seasons of observation. Acceleration sensors were placed in the helmets, and all contact activity was monitored. Pre-season computer-based neuropsychological tests and functional magnetic resonance imaging (fMRI) tests were also obtained in order to assess cognitive and neurophysiological health. In-season follow-up scans were then obtained both from individuals who had sustained a clinically-diagnosed concussion and those who had not. These changes were then related through stepwise regression to history of blows recorded throughout the football season up to the date of the scan. In addition to those subjects who had sustained a concussion, a substantial portion of our cohort who did not sustain concussions showed significant neurophysiological changes. Stepwise regression indicated significant relationships between the number of blows sustained by a subject and the ensuing neurophysiological change. Our findings reinforce the hypothesis that the effects of repetitive blows to the head are cumulative and that repeated exposure to subconcussive blows is connected to pathologically altered neurophysiology.

Acute alcohol intoxication impairs top-down regulation of Stroop incongruity as revealed by blood oxygen level-dependent functional magnetic resonance imaging

Functional neuroanatomy of executive functions has been delineated in a large number of neuroimaging studies using conflict-inducing tasks. The neural basis of alcohol's effects on cognitive control is poorly understood despite the evidence of impaired ability to evaluate competing demands and to inhibit maladaptive responses. To investigate the effects of moderate intoxication, healthy social drinkers participated in both alcohol (0.60 g/kg ethanol for men, 0.55 g/kg for women) and placebo conditions while being scanned using blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI). A modified four-color Stroop task combined reading and color naming and used manual responses. Twenty subjects (10 women) were instructed to press a button corresponding to the font color except when a word was written in gray in which case they had to respond to the meaning of the word. Alcohol increased reaction times and a tendency to make more errors on incongruent trials. Behavioral indices of alcohol-induced premature responding correlated with the current drinking levels and impulsivity traits, suggesting an interaction between alcohol effects and personality predispositions. A distributed frontoparietal cortical network was activated by incongruity. However, moderate alcohol inebriation selectively attenuated anterior cingulate cortex (ACC) activation during both high-conflict trials and erroneous responses, indicating vulnerability of the regulative function subserved by the ACC. By disrupting top-down, strategic processing, alcohol may interfere with goal-directed behavior, resulting in poor self control. The present results support models proposing that alcohol-induced prefrontal impairments diminish inhibitory control and are modulated by dispositional risk factors and levels of alcohol consumption.

Acute effects of alcohol on the human brain: diffusion tensor imaging study

BACKGROUND AND PURPOSE

DTI can provide information about brain ultrastructure by quantifying water diffusion. Our objective was to assess the value of DTI in detecting the acute effects of alcohol on healthy human brains.

MATERIALS AND METHODS

Sixteen healthy volunteers were studied with conventional MR imaging and DTI before and 0.5, 1, 2, and 3 hours after the initiation of acute alcohol administration. Two DTI parameters, FA and ADC, were measured in the frontal lobe, internal capsule, external capsule, precentral gyrus, postcentral gyrus, thalamus, middle cerebellar peduncle, and brain stem. BrACs were measured at each time point after drinking to estimate BACs.

RESULTS

No abnormalities were found by conventional MR imaging at any time point in all subjects. ADC values of the frontal lobe, thalamus, and middle cerebellar peduncle were significantly reduced, reaching a minimum value at 1 or 2 hours, and FA values of the frontal lobe were significantly increased, reaching a maximal value at 0.5 hour in both doses. BrAC (BAC) was significantly increased to reach a peak at 0.5 hour in both doses and decreased gradually.

CONCLUSIONS

DTI can detect changes in brains after acute alcohol consumption that are not detectable by conventional MR imaging. The frontal lobe, thalamus, and middle cerebellar peduncle are more vulnerable to the effects of acute alcohol consumption. DTI is more effective than BrAC or BAC for the detection of alcohol-induced changes on the human brain.

Effects of alcohol intoxication and gender on cerebral perfusion: an arterial spin labeling study

An increasing number of studies use functional MRI (fMRI) and blood oxygen level-dependent (BOLD) signal to investigate the neurofunctional basis of acute alcohol effects on the brain. However, the BOLD signal reflects neural activity only indirectly as it depends on regional hemodynamic changes and is therefore sensitive to vasoactive substances, such as alcohol. We used MRI-based pulsed arterial spin labeling (ASL) method to quantify effects of acute intoxication on resting cerebral perfusion. Gender effects have not been previously examined and yet they are of particular interest given the differences in hormonal dynamics, alcohol metabolism, and hemodynamic regulation. Nineteen young, healthy individuals (nine women) with no personal or familial alcohol- or drug-related problems served as their own controls by participating in both alcohol (0.6g/kg ethanol for men, 0.55g/kg for women) and placebo scanning sessions in a counterbalanced manner. Regionally specific effects of the moderate alcohol dose on gray matter perfusion were examined with voxel-wise and region-of-interest analyses suggesting an interaction between gender and alcohol beverage. Acute intoxication increased perfusion in bilateral frontal regions in men but not in women. Under placebo, stronger cortical perfusion was observed in women compared with men primarily in the left hemisphere in frontal, parietal, and temporal areas. These results emphasize gender differences and regional specificity of alcohol's effects of cerebral perfusion possibly because of interactive influences on hormonal, metabolic, and hemodynamic autoregulatory systems. Alcohol-induced perfusion increase correlated positively with impulsivity/antisocial tendencies, consistent with dopaminergic mediation of reward, and its effects on cortical perfusion. Additional ASL studies are needed to investigate dose- and time-dependent effects of alcohol intoxication and gender on the hemodynamic factors that conjointly influence BOLD signal to disambiguate the vascular/metabolic mechanisms from the neurally based changes.

A selective review of simulated driving studies: Combining naturalistic and hybrid paradigms, analysis approaches, and future directions

Naturalistic paradigms such as movie watching or simulated driving that mimic closely real-world complex activities are becoming more widely used in functional magnetic resonance imaging (fMRI) studies both because of their ability to robustly stimulate brain connectivity and the availability of analysis methods which are able to capitalize on connectivity within and among intrinsic brain networks identified both during a task and in resting fMRI data. In this paper we review over a decade of work from our group and others on the use of simulated driving paradigms to study both the healthy brain as well as the effects of acute alcohol administration on functional connectivity during such paradigms. We briefly review our initial work focused on the configuration of the driving simulator and the analysis strategies. We then describe in more detail several recent studies from our group including a hybrid study examining distracted driving and compare resulting data with those from a separate visual oddball task (Fig. 6). The analysis of these data was performed primarily using a combination of group independent component analysis (ICA) and the general linear model (GLM) and in the various studies we highlight novel findings which result from an analysis of either 1) within-network connectivity, 2) inter-network connectivity, also called functional network connectivity, or 3) the degree to which the modulation of the various intrinsic networks were associated with the alcohol administration and the task context. Despite the fact that the behavioral effects of alcohol intoxication are relatively well known, there is still much to discover on how acute alcohol exposure modulates brain function in a selective manner, associated with behavioral alterations. Through the above studies, we have learned more regarding the impact of acute alcohol intoxication on organization of the brain's intrinsic connectivity networks during performance of a complex, real-world cognitive operation. Lessons learned from the above studies have broader applicability to designing ecologically valid, complex, functional MRI cognitive paradigms and incorporating pharmacologic challenges into such studies. Overall, the use of hybrid driving studies is a particularly promising area of neuroscience investigation.

Functional imaging of cognitive control during acute alcohol intoxication

BACKGROUND

The anterior cingulate and several other prefrontal and parietal brain regions are implicated in error processing and cognitive control. The effects of different doses of alcohol on activity within these brain regions during a functional magnetic resonance imaging (fMRI) task where errors are frequently committed have not been fully explored.

METHODS

This study examined the impact of a placebo [breath alcohol concentration (BrAC) = 0.00%], moderate (BrAC = 0.05%), and high (BrAC = 0.10%) doses of alcohol on brain hemodynamic activity during a functional MRI (fMRI) Go/No-Go task in 38 healthy volunteers.

RESULTS

Alcohol increased reaction time and false alarm errors in a dose-dependent manner. fMRI analyses showed alcohol decreased activity in anterior cingulate, lateral prefrontal cortex, insula, and parietal lobe regions during false alarm responses to No-Go stimuli.

CONCLUSIONS

These findings indicate that brain regions implicated in error processing are affected by alcohol and might provide a neural basis for alcohol's effects on behavioral performance.

Atrophy of the parahippocampal gyrus and regional cerebral blood flow in the limbic system in chronic alcoholic patients

This study investigated regional cerebral flood flow (CBF) in chronic alcoholic patients, focusing primarily on the limbic system, including the hippocampus and the callosomarginal region, because of their susceptibility to damage in such patients. The degree of hippocampal atrophy in such patients was also examined. Regional CBF and the degree of parahippocampal gyrus atrophy were studied in 22 chronic alcoholic male patients with no neurological or psychological symptom (mean age, 59.3+/-4.1 years). Their findings were compared with those of 22 age-matched, male, normal controls (mean age, 59.7+/-3.9 years). Single-photon emission computed tomography was performed using the (99m)Tc-ethylcysteinate dimer ( (99m)Tc-ECD) Patlak Plot method, and the three-dimensional stereotaxic region of interest (ROI) template (3DSRT) and the fine stereotaxic ROI template (fine SRT) developed by Takeuchi et al were used to evaluate regional CBF, focusing primarily on the limbic system. These methods make it possible to precisely and objectively measure the details of regional CBF. The voxel-based specific regional analysis system for Alzheimer's disease (VSRAD) was used to determine the degree of parahippocampal gyrus atrophy in chronic alcoholic patients. VSRAD is a method developed by Hirata et al for evaluating the degree of atrophy of the parahippocampal gyrus. The results were analyzed using Z scores (>2 indicating significant atrophy). Blood flows in the callosomarginal region, pericallosal region, thalamus, hippocampus, parahippocampal gyrus, amygdaloid body, anterior cingulate gyrus, and middle cingulate gyrus were lower in the chronic alcoholic group than in the control group. Parahippocampal gyrus atrophy was not observed in the control group (average Z score, 0.62+/-0.29). In contrast, an atrophic tendency was observed in the chronic alcoholic group (average Z score, 1.88+/-0.44). Clinically intact, chronic alcoholic patients with no neurological or psychological symptom had decreased CBF in the limbic system and a tendency to parahippocampal gyrus atrophy.