MR Volumetric Measurements: We have collected full, volumetric T-1 weighted MR images to measure intracranial volumes several hundred alcoholics and healthy, non-alcoholic subjects. Alcoholics show greater brain degeneration than non-alcoholics. In addition, alcoholics have smaller ICVs than controls suggesting that pre-morbid differences in brain size may contribute to the risk for alcoholism. Despite the significant difference in ICV, degeneration accounts for a greater amount of the difference in brain volume between alcoholics and controls than brain growth does. We have examined how a family history (FH) of heavy drinking affects both brain shrinkage as measured by the ratio of brain volumes to ICV as well as maximal brain growth as measured by ICV in early-onset and late-onset alcoholics. FH positive alcoholic patients have significantly smaller ICVs than FH negative patients, suggesting smaller premorbid brain growth among alcoholics with a heavy drinking mother or father. Brain shrinkage was not affected by FH. Late-onset alcoholics show a greater difference in ICV between FH positive and FH negative patients than early-onset alcoholics. These data provide evidence that heavy parental alcohol use may increase risk for alcoholism in offspring in part by a genetic and/or environmental effect resulting in reduced brain growth. Insula Morphometry: The insula, a structure involved in higher order representation of interoceptive states, has recently been implicated in drug craving and social stress. Here, we performed brain MRI to measure volumes of the insula and subcortical regions with direct insular connections in 26 alcohol dependent patients (ADPs) and 26 healthy volunteers (HVs). In ADPs, anterior insula volumes were bilaterally reduced compared with controls. This reduction was selective, as neither posterior insula nor total brain gray matter volumes differed between groups. In ADPs, we also found increased volume of several subcortical structures that have direct afferent, efferent or reciprocal connections with the insula. Specifically, left and right amygdala, left and right thalami, and the right nucleus accumbens were larger in ADPs than HVs. The amygdala, which demonstrated the greatest volume increase in the alcoholics, has strong reciprocal connections with the insula. Postmortem studies of the anterior insula showed that decrease in the volume of the anterior insula was associated with a diminished population of Von Economo neurons in the subjects with a history of alcoholism (n=6) as compared with the subjects without a history of alcoholism (n=6). The pattern of neuroanatomical change observed in our alcohol dependent patients might result in a loss of top-down control of amygdala function, potentially contributing to an inability to control negatively reinforced alcohol seeking and use (Senatorov et al., manuscript in preparation). MR Diffusion Tensor Measurements: Many brain imaging studies have demonstrated reductions in gray and white matter volumes in alcoholism, with fewer investigators using diffusion tensor imaging (DTI) to examine the integrity of white matter pathways. Among various medical conditions, alcoholism and post-traumatic stress disorder (PTSD) are two comorbid diseases that have similar degenerative effects on the white matter integrity. It is widely believed that these types of abnormalities in both alcoholism and PTSD are related to fronto-limbic dysfunction. DTI was used to measure white matter fractional anisotropy (FA), which provides information about tissue microstructure. We quantitatively investigated the microstructure of white matter through whole brain DTI analysis in 19 healthy volunteers (HV) and 19 alcohol dependent subjects without PTSD (ALC) and with 17 PTSD (ALC+PTSD). These data show significant differences in FA between alcoholics and non-alcoholic HVs, with no significant differences in FA between ALC and ALC+PTSD in any white matter structure. We performed a post-hoc region of interest analysis that allowed us to incorporate multiple covariates into the analysis and found similar results. Relative to all alcoholics, HV had higher FA in several areas implicated in the reward circuit, emotion, and executive functioning, suggesting that there may be microstructural abnormalities in white matter pathways that contribute to neurocognitive and executive functioning deficits observed in alcoholics. Furthermore, our data do not reveal any differences between ALC and ALC+PTSD, suggesting that the effect of alcohol on white matter microstructure may be more significant than any effect caused by PTSD (Durkee et al., manuscript in review). Morphometric Measures: Alcoholism has been associated with a widespread pattern of gray matter atrophy. We sought to investigate the spectrum of volume alterations in a population of alcoholics with only alcohol dependence, polysubstance abusing alcoholics, and a comparison population of healthy controls. Thirty-seven pure alcoholics, 93 polysubstance abusing alcoholics, and 69 healthy controls underwent structural T1 MRI scans. Voxel-based morphometry was performed to investigate gray matter alterations. Alcoholic dependent inpatients (both with and without a history of DSM-IV substance abuse/dependence diagnosis) displayed significant gray matter differences in the mesial region of the frontal lobe and right temporal lobe. Pure alcoholics exhibited a pattern of subcortical changes similar to that seen in Wernicke-Korsakoff Syndrome when compared to polysubstance abusing alcoholics. Pure alcoholics and polysubstance abusing alcoholics did not differ significantly in measures of cortical gray matter, liver function, or nutrition. This study calls for additional research in order to investigate the spectrum from uncomplicated alcoholism to Wernicke-Korsakoff Syndrome (Grodin et al., 2013). Cortical Thickness: Alterations of brain structures have been seen in patients suffering from drug abuse or mental disorders. Similar changes in volume of brain structures have been observed in both alcoholic men and women. We examined the thickness of gray matter in the cerebral cortex in control men and women (n=69, 47 men) and alcohol dependent subjects (n=130, 83 men) to test the hypothesis that alcoholic inpatients would have more cortical damage than controls. Covarying for age and years of education, we confirmed significant differences between alcoholics and healthy controls in cortical thickness in both the left and right hemispheres. Significant differences in cortical thickness between control men and women were also observed. These differences may reflect sexual dimorphisms in the human brain, a genetic predisposition to alcoholism and comorbid drug use, and the extent of gray matter damage in alcoholism and substance use (Momenan et al., 2013). MR Spectroscopy of acute alcohol infusion: We are collaborating with Section on Human Psychopharmacology (Dr. Ramchandani) to measure the effect of acute alcohol infusion on brain metabolites, particularly glutamate, in heavy and light drinkers. We bring human subjects to a steady state BAC of 0.08 g/dl while using MRS scans to measure the concentrations of alcohol, glutamate and other brain metabolites in the subject's brain. Our preliminary results not surprisingly indicate significant differences between brain Ethanol/NAA concentration ratio before and after infusion. However, there was no difference in pre- and post-infusion Glutamate/NAA ratio. When separating the only two Heavy Drinkers in current data set, the Light Drinkers had higher Glutamate/NAA ratio than Heavy Drinkers both before and after the infusion. Interestingly, the Light Drinkers had higher Glutamate/NAA ratio after the infusion. But, the Heavy Drinker subjects had decreased Glutamate/NAA ratio after the infusion.
|Bjork, James M; Momenan, Reza; Hommer, Daniel W (2009) Delay discounting correlates with proportional lateral frontal cortex volumes. Biol Psychiatry 65:710-3|