Clue to why some drinkers blackout found

Washington: Do you often experience a blackout after a night of heavy partying? Then, it could be that your brain has been wired differently, scientists say.

Researchers at the University of Pennsylvania in the US found differences in brain activities among individuals prone to alcohol-induced fragmentary blackouts compared with people who don`t experience such conditions.

They found that the two "party types" did not differ in performance on a memory task while sober, but did exhibit different brain-response patterns after alcohol intoxication.

This suggests a neurobiological mechanism associated with alcohol-induced fragmentary blackouts, the researchers said.

"It could be that their brains are just wired differently. Or it could be underlying things going on, like differences in dopamine levels," study author Reagan Wetherill was quoted as saying by 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 -- 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.

For their study, to be published in the June edition of journal Alcoholism: Clinical & Experimental Research, the team studied a group of 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 were then divided into two groups: those who have a history of blackouts and those who don`t, 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, the team 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," he said, adding that these blackouts can have negative consequences, like not remembering risky sex or driving while intoxicated and not remembering it.