“In the eyes of the law, once people reach the age of 18, they are considered adult, but the brain continues to mature and refine all the way into the mid-20s,” said lead author Mary-Louise Risher, a post-doctoral researcher in Duke’s Department of Psychiatry and Behavioral Sciences. “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.
Studies had shown that animals exposed to alcohol at an early age do not perform as well in memory tasks as those not exposed to it. The new study, which involved exposing young rodents to alcohol and waiting for them to grow into adulthood, found that the exposure also affects the hippocampus, the area of the brain that controls memory and learning. The researchers measured a cellular mechanism called long-term potentiation, which involves the strengthening of brain synapses being used to learn new tasks or bring up memories. Ideally, LTP should be high, especially in young people. The researchers found that the adult rodents exposed to the alcohol during adolescence had higher levels of LTP, which may seem to be a positive outcome but is actually not.
“If you produce too much LTP in one of these circuits, there is a period of time where you can’t produce any more,” said senior author Scott Swartzwelder, a Duke professor. “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.”
The researchers also observed a structural change in individual nerve cells: those exposed to alcohol at a young age have brain cells that appear immature, even in adulthood. “It’s quite possible that alcohol disrupts the maturation process, which can affect these cognitive functions later on,” Risher said. She also noted that the immature appearance of the cells might be associated with behavioral immaturity.