Researchers know that years of alcohol abuse can damage someone’s brain. Although both genders seem to be affected by alcohol’s toxic neurological effects, women often have shorter histories of heavy drinking before experiencing the same effects. This suggests that women may have a more heightened sensitivity to the effects of alcohol. A study in the February issue of Alcoholism: Clinical & Experimental Research uses a variant of magnetic resonance imaging (MRI) to closely examine brain function in young alcoholic women.
"Previous studies have shown that alcoholic women perform just as poorly as alcoholic men on thinking and memory tests," said Susan F. Tapert, first author of the study, "even though the women hadn't been drinking as long as the men had." Furthermore, added Tapert, also an assistant adjunct professor at the VA San Diego Healthcare System and the University of California at San Diego, recent research using MRI has found that alcoholic teens may have shrinkage of a brain part - called the hippocampus - that is critical for memory.
"We have ourselves done several studies comparing thinking and memory abilities in teens with and without drinking problems," Tapert continued, "and found that remembering information, solving spatial problems like working with maps or puzzles, and doing mental arithmetic were less accurate in heavy-drinking youth. With our brain imaging study, we wanted to understand what parts of the brain might explain these thinking and memory problems. We wanted to examine what brain parts might have been affected by heavy drinking during these women’s youth, and how those brain parts function when called upon." Tapert and her colleagues used what is called functional MRI (fMRI) to identify the areas of disturbed brain functioning.
The human brain is composed of approximately 90 percent water. Structural MRI is especially sensitive to the detection of water molecules, which means it can yield remarkably high-resolution images of the brain. Scientists can then manipulate image data to differentiate among the three principal tissue types in the brain: gray matter (cell bodies), white matter (fiber tracts connecting cell bodies), and cerebrospinal fluid (which fills cavities in the brain). Functional MRI uses the same hardware as MRI but is more sensitive to changes in blood flow related to changes in cognitive, motor, or sensory tasks performed by individuals while they are being scanned. Typically, fMRI reflects a change in activity between two tasks that differ in only one aspect. The signals obtained from the two different conditions are then subtracted from one another and the remaining regions of the brain that demonstrate significant activation are interpreted as having contributed to the task. In other words, MRI provides a very clear picture of the brain so that the size and shape of brain parts can be examined. FMRI takes pictures of the brain every few seconds, so that researchers can paste together what Tapert calls a "movie" of activity in the brain while the subject is doing a mental task.
"FMRI allowed us to examine very subtle changes in blood and oxygen use in the brain while our subjects did tasks that are difficult for young heavy drinkers," said Tapert. After ensuring that all study participants had been abstinent from alcohol for at least 72 hours, researchers tested their cognitive (or thinking) abilities and mood before the fMRI, and working memory abilities both before and during the fMRI.
Certain areas of the frontal and parietal lobes of the brain, even though they are physically distant from each other, are intimately connected through brain circuitry. A number of studies have shown that this brain circuit becomes active when subjects perform working memory tasks. In most people, working memory tasks that require spatial processing of visually presented material rely more heavily on right than left hemisphere function. In this study, the alcoholic women failed to show a ‘normal’ pattern of activation while performing their visual spatial working memory task.
"Compared with the nonalcoholics," explained Edith V. Sullivan, associate professor of psychiatry at Stanford University School of Medicine, "the young women with alcohol dependence appeared to engage their cortical systems less vigorously. In some cases, the brain systems activated by the alcoholic women were different from those activated by individuals with no alcohol problems. One interpretation of these differences is that the alcoholic women tend to invoke brain systems that are less appropriately tuned for the task at hand, or perhaps the activation is not as intense as it might be without their history of alcohol dependence."
"The main finding," said Tapert, "was that the alcohol-dependent women showed less activation in brain areas that are needed for spatial tasks like puzzles, maps and mechanics, and for working with information that is held mentally, like doing math inside your head or making sense of a lecture or set of complex instructions. The brain parts that showed the differences are in areas that we need for finding our way around, and working with all the information we are bombarded with in everyday life." Furthermore, Tapert added, these findings suggest that even young and physically healthy individuals, particularly if they are female, risk damaging their brains through chronic, heavy use of alcohol.
"It is now well-established," said Sullivan, "that adults with years of chronic alcoholism suffer enduring mild to moderate cognitive and motor deficits even long after detoxification and with long-term sobriety. Before the advent of functional imaging technologies, we could only speculate what areas of the brain caused the performance deficits observed in life. Now, fMRI enables us to identify with reasonably good precision circumscribed fields of brain activation occurring in conjunction with specific, experimentally controlled tasks. Previous studies that relied on behavioral testing had consistently reported alcoholism-related deficits in visuospatial nonverbal working memory. The Tapert study has both confirmed and extended speculations about the neural substrates of visuospatial nonverbal working memory deficits. In short, this study has demonstrated that even young women with alcohol dependence suffer significant aberrations in brain and cognitive function and that this pattern of abnormalities is similar to that documented in older alcoholics with many years of abusive drinking."
Both Tapert and Sullivan see the need for researchers to continue tracking the changes in cognitive and motor abilities that are caused by chronic alcohol abuse.
"We want to better understand if drinking directly causes the brain abnormalities," said Tapert, "or if there were pre-existing differences. We would also like to understand how much drinking is required to produce these changes and how these problems recover with abstinence." Tapert said that teens, college-age people, and their parents need to be aware that abstinence from alcohol may not necessarily reverse the negative changes caused by alcohol abuse. "It may pay off later to drink less now," she said.