The Inner Workings of an Alcohol Blackout

The Inner Workings of an Alcohol Blackout

Story and Photo by Hudson Lofchie

Published January 24th, 2011 in the Californa Aggie (theaggie.org)

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Whisky, Gin, what a night it has been. Taste unbearable, potency strong. Takes the mind from right to wrong.

The signs of drunkenness are familiar to anyone on a college campus. The stumbling, slurred speech, unadulterated arrogance and machismo all combine to paint a humorous picture of what alcohol can do to a body. That humor ends, however, when we see what havoc the brew is wreaking on our brains.

“Excess alcohol in the system causes brain cells to go to sleep, but since the body stays awake, there is no memory of what was said or done,” said Stephanie Lake, the Alcohol and Drug Abuse Prevention and Treatment coordinator at UC Davis.

When alcohol enters the body, it is processed in the liver by an enzyme called alcohol dehydrogenase. This enzyme breaks down alcohol into a chemical called acetaldehyde, which combines with oxygen to make carbon dioxide. That carbon dioxide is what we exhale into breathalyzers. Leftover acetaldehyde is the second leading cause of hangovers, after dehydration.

“High blood alcohol content (BAC) impairs the ability of the brain to create new long-term memories of event and facts,” said Lauren Liets, a neurobiology, physiology and behavior professor here at UC Davis. “Blackouts are a form of anterograde amnesia.”

That means that memories before the blackout remain intact.

According to a National Institutes of Health alcohol study, “the liver has the ability to metabolize only about .25 ounces of alcohol per hour.” This leaves the remaining alcohol to travel through the bloodstream, and to the brain. For comparison, a shot of Skyy vodka and a can of Heineken each have three-fifths of an ounce of alcohol, more than we can process per hour. It is this remaining alcohol that causes the impairments associated with drinking.

Nearly all toxins are prevented from entering the brain by the blood-brain barrier. However, alcohol’s molecular structure allows it to pass through the barrier uninhibited. Once in the brain, alcohol effects the hippocampus, where memories are formed, and the frontal cortex, where critical thinking, decision making and risk assessment are located. This interference with frontal lobe function is what causes the cocky, careless behavior indicative of intoxication.

Our memories are formed in the hippocampus by interactions between neurons and a receptor known as N-methyl-D-asparate (NMDA). Alcohol binds to NMDA and renders it unable to properly form memories. When alcohol is present in excess, it can lead to a complete lack of memory formation. Until your liver’s enzymes can process the remaining alcohol, the frontal lobe will be unable to properly create memories.

Other affected areas of the brain include the limbic system and hypothalamus.

“Alcohol in the limbic system affects the reward response, and triggers mechanisms of addiction, as well as affecting balance and movement,” said Liets.

Alcohol in the limbic system also causes an exaggerated emotional state and increased sexual desire. Ironically, at the same time that alcohol increases feelings of sexual desire in the limbic system, it adversely affects hormone production in the hypothalamus and pituitary gland, resulting in greatly decreased sexual function and performance.

Some science sounds like it’s straight out of Beerfest. In 1995, researchers from Washington University in St. Louis, found that alcohol can create “context or state dependent memories,” or in layman’s terms, Drunken Recall. This means that while sober, you may be completely unable to remember what you did while intoxicated, but when you return to an intoxicated state, you can more easily remember where you hid all of your roommate’s textbooks.

HUDSON LOFCHIE can be reached at science@theaggie.org. Follow him on Twitter @HudtacularSci.

Written by Hudson Lofchie

Science Writer

Published on Jan 12, 2011 in The California Aggie (theaggie.org)

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