WASHINGTON

NEW Year’s Eve tends to be the day of the year with the most binge drinking (based on drunken driving fatalities), followed closely by Super Bowl Sunday. Likewise, colleges have come to expect that the most alcohol-filled day of their students’ lives is their 21st birthday. So, some words of caution for those who continue to binge and even for those who have stopped: just as the news is not so great for former cigarette smokers, there is equally bad news for recovering binge-drinkers who have achieved a sobriety that has lasted years. The more we have binged — and the younger we have started to binge — the more we experience significant, though often subtle, effects on the brain and cognition.

Much of the evidence for the impact of frequent binge-drinking comes from some simple but elegant studies done on lab rats by Fulton T. Crews and his former student Jennifer Obernier. Dr. Crews, the director of the University of North Carolina Bowles Center for Alcohol Studies, and Dr. Obernier have shown that after a longstanding abstinence following heavy binge-drinking, adult rats can learn effectively — but they cannot relearn.

When put into a tub of water and forced to continue swimming until they find a platform on which to stand, the sober former binge-drinking rats and the normal control rats (who had never been exposed to alcohol) learned how to find the platform equally well. But when the experimenters abruptly moved the platform, the two groups of rats had remarkably different performances. The rats without previous exposure to alcohol, after some brief circling, were able to find the new location. The former binge-drinking rats, however, were unable to find the new platform; they became confused and kept circling the site of the old platform.

This circling occurs, Dr. Crews says, because the former binge-drinking rats continued to show neurotoxicity in the hippocampus long after (in rat years) becoming sober. On a microscopic level, Dr. Crews has shown that heavy binge-drinking in rats diminishes the genesis of nerve cells, shrinks the development of the branchlike connections between brain cells and contributes to neuronal cell death. The binges activate an inflammatory response in rat brains rather than a pure regrowth of normal neuronal cells. Even after longstanding sobriety this inflammatory response translates into a tendency to stay the course, a diminished capacity for relearning and maladaptive decision-making.

Studies have also shown that binge drinking clearly damages the adolescent brain more than the adult brain. The forebrain — specifically the orbitofrontal cortex, which uses associative information to envision future outcomes — can be significantly damaged by binge drinking. Indeed, heavy drinking in early or middle adolescence, with this consequent cortical damage, can lead to diminished control over cravings for alcohol and to poor decision-making. One can easily fail to recognize the ultimate consequences of one’s actions.

Does the research on rats have relevance for the more complex brains and behavior of humans? We have come to think so. Dr. Crews has shown that the cingulate cortex in the human brain shows signs of neuroinflammation after repeated alcohol binges, similar to that in rats. Sidney Cohen, one of the clearest thinkers and researchers on the effects of alcohol and drugs on humans (now deceased, he was at one time the director of the drug abuse division at the National Institute of Mental Health), pointed out that we are programmed as a species for accelerated learning in adolescence and young adulthood. This heightened capacity is the reason we go into apprenticeships or on to college and graduate school in these crucial years.

As Dr. Cohen noted, we not only learn specific skills during these years, with our brains having developed more fully, we also learn in a more subtle way how to deal with ambiguity. Ambiguity comes into play when the goalposts are moved. Can we change course? Can we deal with this ambiguity and with nuances?

The one piece of good news is that exercise has been shown to stimulate the regrowth and development of normal neural tissue in former alcohol-drinking mice. In fact, this neurogenesis was greater in the exercising former drinking mice than that induced by exercise in the control group that had never been exposed to alcohol.

So, some possible resolutions for the New Year:

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Stop after one or two drinks. Studies of the Mediterranean diet have shown that one or two drinks on a consistent basis leads to a longer life than pure teetotaling.

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If you must binge, start at age 40, not at age 16 — and always have someone else drive. Just as youth is wasted on the young, so perhaps is alcohol.

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If you have binged excessively when younger, follow it up with some regular exercise. Get those brain cells regenerated.

As Shakespeare once pointed out without the benefit of studies on lab rats, “O God, that men should put an enemy in their mouths to steal away their brains!”