Diffusion-weighted magnetic resonance imaging at 3.0 Tesla in alcohol intoxication

Effects of acute alcohol exposure and chronic alcohol use on neurite orientation dispersion and density imaging (NODDI) parameters

RATIONALE

Little is known about how acute and chronic alcohol exposure may alter the in vivo membrane properties of neurons.

OBJECTIVES

We employed neurite orientation dispersion and density imaging (NODDI) to examine acute and chronic effects of alcohol exposure on neurite density.

METHODS

Twenty-one healthy social drinkers (CON) and thirteen nontreatment-seeking individuals with alcohol use disorder (AUD) underwent a baseline multi-shell diffusion magnetic resonance imaging (dMRI) scan. A subset (10 CON, 5 AUD) received dMRI during intravenous infusions of saline and alcohol during dMRI. NODDI parametric images included orientation dispersion (OD), isotropic volume fraction (ISOVF), and corrected intracellular volume fraction (cICVF). Diffusion tensor imaging metrics of fractional anisotropy and mean, axial, and radial diffusivity (FA, MD, AD, RD) were also computed. Average parameter values were extracted from white matter (WM) tracts defined by the Johns Hopkins University atlas.

RESULTS

There were group differences in FA, RD, MD, OD, and cICVF, primarily in the corpus callosum. Both saline and alcohol had effects on AD and cICVF in WM tracts proximal to the striatum, cingulate, and thalamus. This is the first work to indicate that acute fluid infusions may alter WM properties, which are conventionally believed to be insensitive to acute pharmacological challenges. It also suggests that the NODDI approach may be sensitive to transient changes in WM. The next steps should include determining if the effect on neurite density differs with solute or osmolality, or both, and translational studies to assess how alcohol and osmolality affect the efficiency of neurotransmission.

Prospective memory deficits following acute alcohol consumption

BACKGROUND

Prospective memory is a critical neurocognitive capacity that refers to the ability to execute delayed intentions. To date, few studies have investigated the effects of acute alcohol consumption on prospective memory, and important questions remain about the mechanisms that might underpin acute alcohol-induced prospective memory impairment.

AIMS

The current study sought to clarify the nature and magnitude of prospective memory difficulties following acute alcohol consumption and to test the degree to which any problems with prospective remembering might be a secondary consequence of broader cognitive impairment. This study also investigated whether there were potential sex differences.

METHODS

In all, 124 healthy adult social drinkers were assigned to either the alcohol (n = 61) or placebo (n = 63) condition. Participants were administered a dose of 0.6 g/kg alcohol or a matched placebo drink and then asked to complete a measure of prospective memory. A broader neurocognitive test battery was also administered.

RESULTS

Relative to the placebo condition, acute alcohol intoxication led to significant impairment on all prospective memory tasks, with effects mostly large in magnitude. These difficulties could not be explained by broader problems in retrospective memory, executive function or episodic future thinking. In addition, females recorded a higher blood alcohol concentration than males; however, no sex differences in prospective memory performance were identified following acute alcohol use.

CONCLUSION

The results show that acutely, even a moderate dose of alcohol substantially impairs prospective memory function. These findings have potentially important implications for understanding many of the maladaptive behaviours associated with acute alcohol consumption.

Changes in the brain directly following alcohol consumption-a study of healthy male individuals, with the use of proton magnetic resonance spectroscopy (1HMRS) and diffusion (DWI)

AIMS

To use proton magnetic resonance spectroscopy (1HMRS) and diffusion weighted imaging (DWI) to identify ethanol in the brain directly after consumption, and examine changes in brain metabolite levels and brain microstructure relative to the duration of time following exposure to alcohol.

METHODS

The study involved 44 male volunteers (18-55 years). All brain changes were assessed in the frontal lobes, occipital lobes, basal ganglia and cerebellum, however the detailed analyses focused on the frontal lobes. All participants were examined four times, i.e. before and 0.5-hour, 1 hour and 2 hours after consumption of 150 mL pure vodka (60 g of ethanol).

RESULTS

The highest ethanol levels were identified between 0.5 and 1 hour following alcohol intake. There were significant increases in the concentrations of lipids and lactates approximately one hour after alcohol consumption, and the concentration levels were found to normalise during the following two hours. Some statistically insignificant trends of changes were found for tCr, tCho, mI, GABA, Glc, Glx and tNAA. For the DWI and ADC (Apparent Diffusion Coefficient of water) values, the findings showed statistically insignificant decrease and increase, followed by a tendency towards normalisation. Similar associations in changes of metabolite concentrations and DWI and ADC values were found in the other locations investigated in the study.

CONCLUSION

A single dose of alcohol as used in this experiment produces increases in lipids and lactates in brain tissues that appear reversible.

Effects of Acute Alcohol Consumption on the Human Brain: Diffusional Kurtosis Imaging and Arterial Spin-Labeling Study

BACKGROUND AND PURPOSE

Brain function and microstructure are affected by alcohol consumption. Until recently, the effect of alcohol on neural mechanisms has not been fully elucidated. Our aim was to explore the acute effects of alcohol on healthy human brains by diffusional kurtosis imaging and 3D arterial spin-labeling and elucidate structural and functional changes in the brain on acute alcohol intake.

MATERIALS AND METHODS

Conventional MR imaging, diffusional kurtosis imaging, and 3D arterial spin-labeling were performed on 24 healthy volunteers before and 0.5 and 1 hour after drinking alcohol. Participants were divided into 2 groups according to the response to alcohol: blushing (n = 12) and unblushing (n = 12) groups. Twenty brain regions were analyzed.

RESULTS

Diffusional kurtosis imaging revealed an increase in mean kurtosis and fractional anisotropy at 0.5 hour post-alcohol intake in most brain regions, whereas mean diffusion was decreased in several brain regions at 1 hour after drinking. 3D arterial spin-labeling showed increased cerebral blood flow in most brain regions, particularly in the frontal regions. However, perfusion in the anterior commissure decreased. Regional changes in the brain correlated with various behavioral performances with respect to blush response and sex. In general, blushing individuals and men are more sensitive to alcohol with acute effects.

CONCLUSIONS

Physiologic and microstructural alterations in the brain on alcohol consumption were examined. Brain areas with blood flow alteration detected by 3D arterial spin-labeling were highly consistent with susceptible areas detected by diffusional kurtosis imaging. The current study provides new insight into the effects of alcohol on the brain and behavioral performance in different blush response and sex populations.

Effects of acute alcohol intoxication on executive functions controlling self-regulated behavior

Alcohol consumption may lead to deficits in the executive functions that govern self-regulation. These deficits could lead to risk-taking behaviors; therefore, it is important to determine the magnitude of these deficits on executive functioning. The purpose of this experiment was to investigate the acute effects of alcohol on three of the executive functions that are hypothesized to affect self-regulation, which are inhibition, set shifting, and working memory, using a mixed-methods study design. The participants were 75 moderate or heavy drinkers between the ages of 21 and 35 who were randomized into one of three beverage conditions (control, placebo, or 0.65-g alcohol dose/kg body weight). Performance on working memory, set shifting, and inhibition were measured pre- and post-beverage consumption. The results showed only a significant interaction in the working memory data, as there was an increase in performance post-beverage relative to pre-beverage for the control participants as compared to the alcohol and placebo participants. It was concluded that the dose of alcohol (BAC = 0.063%) given to moderate to heavy drinkers was not sufficient to cause significant impairment in the executive functions tested. The results were further discussed and methodological concerns were considered, such as the low BAC achieved, practice effects, and insensitivity of tasks.

Acute ethanol-induced changes in edema and metabolite concentrations in rat brain

The aim of this study is to describe the acute effects of EtOH on brain edema and cerebral metabolites, using diffusion weight imaging (DWI) and proton magnetic resonance spectroscopy ((1)H-MRS) at a 7.0T MR and to define changes in apparent diffusion coefficient (ADC) values and the concentration of metabolites in the rat brain after acute EtOH intoxication. ADC values in each ROI decreased significantly at 1 h and 3 h after ethanol administration. ADC values in frontal lobe were decreased significantly compared with other regions at 3 h. For EtOH/Cr+PCr and cerebral metabolites (Cho, Tau, and Glu) differing over time, no significant differences for Ins, NAA, and Cr were observed in frontal lobes. Regression analysis revealed a significant association between TSEtOH/Cr+PCr and TSCho, TSTau, TSGlu, and TSADC. The changes of ADC values in different brain regions reflect the process of the cytotoxic edema in vivo. The characterization of frontal lobes metabolites changes and the correlations between TSEtOH/Cr+PCr and TSCho, TSTau, and TSGlu provide a better understanding for the biological mechanisms in neurotoxic effects of EtOH on the brain. In addition, the correlations between TSEtOH/Cr+PCr and TSADC will help us to understand development of the ethanol-induced brain cytotoxic edema.

Dose-related effects of alcohol on cognitive functioning

We assessed the suitability of six applied tests of cognitive functioning to provide a single marker for dose-related alcohol intoxication. Numerous studies have demonstrated that alcohol has a deleterious effect on specific areas of cognitive processing but few have compared the effects of alcohol across a wide range of different cognitive processes. Adult participants (N = 56, 32 males, 24 females aged 18–45 years) were randomized to control or alcohol treatments within a mixed design experiment involving multiple-dosages at approximately one hour intervals (attained mean blood alcohol concentrations (BACs) of 0.00, 0.048, 0.082 and 0.10%), employing a battery of six psychometric tests; the Useful Field of View test (UFOV; processing speed together with directed attention); the Self-Ordered Pointing Task (SOPT; working memory); Inspection Time (IT; speed of processing independent from motor responding); the Traveling Salesperson Problem (TSP; strategic optimization); the Sustained Attention to Response Task (SART; vigilance, response inhibition and psychomotor function); and the Trail-Making Test (TMT; cognitive flexibility and psychomotor function). Results demonstrated that impairment is not uniform across different domains of cognitive processing and that both the size of the alcohol effect and the magnitude of effect change across different dose levels are quantitatively different for different cognitive processes. Only IT met the criteria for a marker for wide-spread application: reliable dose-related decline in a basic process as a function of rising BAC level and easy to use non-invasive task properties.

Effects of alcohol on tests of executive functioning in men and women: a dose response examination

Alcohol has been shown to affect performance on tasks associated with executive functioning. However, studies in this area have generally been limited to a single dose or gender or have used small sample sizes. The purpose of this study was to provide a more nuanced and systematic examination of alcohol's effects on commonly used tests of executive functioning at multiple dosages in both men and women. Research volunteers (91 women and 94 men) were randomly assigned to one of four drink conditions (alcohol doses associated with target blood alcohol concentrations of .000%, .050%, .075%, and .100%). Participants then completed three tasks comprising two domains of executive functioning: two set shifting tasks, the Trail Making Test and a computerized version of the Wisconsin Card Sorting Task, and a response inhibition task, the GoStop Impulsivity Paradigm. Impaired performance on set shifting tasks was found at the .100% and .075% dosages, but alcohol intoxication did not impair performance on the GoStop. No gender effects emerged. Thus, alcohol negatively affects set shifting at moderately high levels of intoxication in both men and women, likely attributable to alcohol's interference with prefrontal cortex function. Although it is well established that alcohol negatively affects response inhibition as measured by auditory stop-signal tasks, alcohol does not appear to exert a negative effect on response inhibition as measured by the GoStop, a visual stop-signal task.