A new study finds that drinking alcohol can improve recall of learning that occurs before a drinking session, and that this effect is stronger with greater alcohol consumption.
The reason for the finding is not fully understood, say researchers from the University of Exeter in the United Kingdom, who report it in the journal Scientific Reports.
It has been suggested, they note, that alcohol stops the brain being able to take on new information, freeing up resources to more firmly bed down earlier learning.
"The theory is that the hippocampus - the brain area really important in memory - switches to 'consolidating' memories, transferring from short- into longer-term memory," explains senior study author Celia Morgan, a professor of psychopharmacology at the University of Exeter.
However, she and her team wish people to realize that that their findings point to a "limited effect" that should be weighed up against the well-known negative consequences on memory and mental and physical health that result from excessive alcohol consumption.
First study in 'naturalistic setting'
In their study paper, the team explains that there is a lot of documented evidence on the effects of alcohol on memory performance. This shows, for example, that people under the influence of alcohol are less able to form new memories.
And, paradoxically, there is also evidence that alcohol can improve memory when the information is learned before intoxication takes place.
Thus, while the new study is not the first to observe this effect, it is the first to demonstrate it in a "naturalistic setting," outside the laboratory. The setting for the study was the participants' own homes.
The authors also note that, "Since alcohol is the most popular recreational drug worldwide, with an estimated 38.3 percent of the global population currently using it, investigating the naturalistic effects of alcohol is important in assessing the harms and potential benefits of this ubiquitous substance."
For their investigation, Prof. Morgan and colleagues recruited 88 social drinkers (31 men and 57 women), aged between 18 and 53, and they randomly assigned them to one of two groups: the alcohol group and the sober group.
All participants undertook a word-learning task in a quiet room at home in the early evening. This was followed by a first test of recall.
Those in the alcohol group were then invited to drink as much alcohol as they wished, and those in the sober group were asked to drink only nonalcoholic drinks.
Improved recall of pre-drinking learning
The next morning, the participants undertook a second test to recall the words that they had learned the evening before. This test took place around 18 hours after the learning task.
The results showed that the performance in the second recall test (that is, following the drinking session) was better than in the first recall test (before the drinking session) for the alcohol group only.
"Our research not only showed that those who drank alcohol did better when repeating the word-learning task, but that this effect was stronger among those who drank more."
Prof. Celia Morgan
The researchers suggest that the reason that greater consumption of alcohol might improve recall of pre-drinking learning might be that alcohol creates a state in the brain that "better facilitates cellular and systems consolidation as dose increases."
They also note that there could be an interaction between the effect of sleep and the effect of alcohol, as the second recall test was done the following morning, after a night's sleep.
The team suggests that future studies should attempt to "empirically rule out alternative neurobiological explanations for retrograde facilitation by controlling for sleep."
Memory no better after intoxicated learning
The participants also underwent a second experiment, in which the learning task took place under the influence of alcohol.
They completed the learning phase of the second experiment, which involved looking at images on a screen and then undergoing a first test of recall, shortly after the drinking session, before they went to bed.
The second test of recall for this post-drinking memory task also took place the next morning, shortly after the word-learning recall test.
The results showed no significant improvement in recall between the two tests for the alcohol group.
Prof. Morgan and team conclude that their findings "support the notion that alcohol can facilitate memory for previously learned information."