We have collected full, volumetric T-1 weighted MR images using a 1.5 T scanner to measure intracranial volumes in 350 alcoholics (248 males and 112 females) and 163 healthy, non-alcoholic comparison subjects (82 males and 81 females). An automated segmentation program was used to divide the intracranial contents into CSF, gray and white matter (Human Brain Mapping, 5:194-205, 1997). When we measure brain volume we are measuring the combined effect of two processes: growth and degeneration. Growth determines maximum brain size achieved during life. Maximal brain growth can be estimated by intracranial volume (ICV) and since ICV remains constant throughout life, measuring ICV anytime after adolescence provides reliable data on maximal brain growth. In addition, degeneration can be measured by the ratio of cerebral volume or gray matter or white matter volume to the remainder of the intracranial contents. Alcoholics show greater brain degeneration than non-alcoholics. Alcoholic women are more affected than alcoholic men. Alcoholics also show significantly greater brain shrinkage than controls by their mid to late twenties. In addition, alcoholics have smaller intracranial volumes than controls suggesting that pre-morbid differences in brain size may contribute to the risk for alcoholism. Despite the significant difference in intracranial volume brain, degeneration accounts for a greater amount of the difference in brain volume between alcoholics and controls than brain growth does. Similarly, presence or absence of co-morbid psychiatric disorder or other substance abuse does not affect brain shrinkage among alcoholics. Over the past few years we have made several methodological advances in the automated measurement of brain volumes. An automated method for dividing the brain into right and left hemispheres was developed and validated. In addition, we have developed an automated method for measuring the volume of mesial and orbital frontal cortex, as well as the entire striatum. These regions are known to be involved in motivation and social behavior. We have begun to investigate the normal and pathological development of the striatum. It appears that children and adolescents at risk for the development of alcoholism have significantly smaller striatums, including nucleus accumbens, than child not at high risk for the development of alcoholism. In addition, we have also examined how a family history (FH) of heavy drinking affects both brain shrinkage as measured by the ratio of brain volumes to intracranial volume 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 motr 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. Late-onset FH positive patients also have significantly lower IQ scores than late-onset FH negative patients, and IQ scores are correlated with ICV. 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. We have also completed specific investigations of frontal lobe volume in alcoholics and controls. Alcoholics appear to have smaller frontal lobe volumes than controls. This reduction in frontal volume is restricted to the mesial surface of the right frontal lobe. We have also found that among healthy subjects that the tendency to devalue delayed rewards (delay discounting), which is considered an excellent laboratory measure of impulsivity, is associated with shrinkage of the lateral surface of the frontal lobes. The lateral frontal lobe is the same region that has been shown to be activated during delayed discounting tasks during functional imaging. Thus our results are consistent with the functional neuroanatomy of human impulsivity and may be important in understanding brain differences associated with risk for the development of substance abuse.
