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New study explains why some drinkers black out

By Jennifer Welsh

After a night of heavy partying, you might need a few clues to piece together your night. New research suggests that some people are more susceptible than others to blackouts and memory loss after tossing a few back.

The differences between the two "party types" are visible in their brains, with those prone to blackouts showing different responses in brain areas involved in memory and attention processes after ingesting just a slight amount of alcohol, compared with people who don't blackout.

"It could be that their brains are just wired differently. Or it could be underlying things going on, like differences in dopamine levels," study researcher Reagan Wetherill, Ph.D., at the University of Pennsylvania, told LiveScience. "Some people are made differently and are able to handle things such as alcohol and others just aren't."

The researchers are studying what's technically called an "alcohol-induced fragmentary blackout" — what some might call a brownout — a time when memories get spotty due to alcohol drinking.

"The fragmentary blackout is basically partial memory loss after a drinking episode. You can remember bits and pieces of things, once you are given clues," Wetherill said. "You are conscious and participating in these complex behaviors, but the brain isn't necessarily online, taking in the information and remembering what's going on."

These blackouts can have negative consequences, like not remembering risky sex or driving while intoxicated and not remembering it. They aren't studying full-on blackouts, but those would be a logical extension of this work: The more alcohol, the more complete the blackout, Wetherill said.

The researchers studied 24 college students who routinely have two or three nights out with about five drinks per night, an amount considered binge drinking in science circles. They separated them into two groups: those who have a history of blackouts and those who don't (though they were matched up in pairs based on their level of drinking experience), and scanned their brains while they were performing a memory task, either sober or after a few drinks.

When sober, these two groups showed very similar brain patterns. After even slight amounts of drinking, to the legal limit of 0.08, or two beers or glasses of wine (depending on your size), the researchers saw big differences in brain activity during the games.

For instance, those prone to blackouts showed decreased activity in parts of the brain responsible for turning experiences into memories and those involved with attention and cognitive functioning.

The day after the drunken memory trial, the researchers called to check in on their subjects. None of the participants reported having fragmented memories of the test while it was happening, even though brain scans would beg to differ; the mismatch suggests the "blackout brain" was acting differently even before it started forgetting.

"What could be happening is that some individuals have a brain which can handle or compensate to a certain point but if you put a cognitive load on it, like alcohol, it just gets overloaded," Wetherill said. "Things just aren't working as efficiently."

The study will be published in the June 2012 issue of the journal Alcoholism: Clinical & Experimental Research.

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