Study Shows Repeat Exposure to Alcohol during Adolescence Results in Long-Term Brain Changes

Repeated use of alcohol during adolescent years leads to long-lasting, detrimental changes to the memory and learning areas of the brain, according to findings from a Duke University Medical Center research group.

A recently published study from the journal Alcoholism: Clinical & Experimental Research reveals that individuals over-exposed to alcohol at an age when the brain isn’t fully developed can experience synaptic and cellular abnormalities that have continuing effects on behavior.

Researchers say that while the United States legally recognizes individuals as adults at age 18, brain development and maturity continues until the mid-20s. “It's important for young people to know that when they drink heavily during this period of development, there could be changes occurring that have a lasting impact on memory and other cognitive functions,” said the study’s lead author, Mary-Louise Risher, PhD, in a news release. Risher is a post-doctoral researcher from the Duke Department of Psychiatry and Behavioral Sciences.

Risher and colleagues, including professor of Psychiatry and Behavioral Sciences at Duke and senior author Scott Swartzwelder, PhD, exposed young rodents at specific intervals to an alcohol level that would result in impairment, but not sedation, in humans. After completing the regiment, these animals were not exposed to anymore alcohol and matured into adulthood, which occurs from 24 to 29 days among rat populations.

The researchers measured a cellular mechanism known as long-term potentiation (LTP) by applying small, electrical stimuli to the hippocampus region of the brain. LTP is the brain’s process of strengthening synapses as they are utilized to recount memories or learn new tasks. LTP is highest in young people, and learning is optimal when this synaptic activity is robust enough to form strong signal transmissions between neurons.

From earlier studies, research has revealed that adolescent animals exposed to alcohol grow into adults that are substantially less skilled at memory tasks that normal animals, but it wasn’t understood how these impairments manifest in the hippocampus. The Duke team expected to find highly diminished LTP in the adult rats exposed to alcohol, but the opposite was detected. LTP was hyperactive in these animals compared to the test group unexposed to alcohol. 

"At first blush, you would think the animals would be smarter," Swartzwelder said in the news article. "But that's the opposite of what we found. And it actually does make sense, because if you produce too much LTP in one of these circuits, there is a period of time where you can't produce any more. The circuit is saturated, and the animal stops learning. For learning to be efficient, your brain needs a delicate balance of excitation and inhibition -- too much in either direction and the circuits do not work optimally."

Risher, Swatzwelder and colleagues discovered a structural change in each individual nerve cell that accompanied the LTP irregularity. Risher explains that this immature quality of the brain cells might be associated with behavioral immaturity as well as affect impulse and emotion control.

For a complete version of the study, click here.