If you've ever crammed for an exam, then you probably remember how stressful it was trying to learn everything you read as your exam loomed closer. But how exactly were you able to remember all those things, with stress levels rising and your frustration growing? Well, one group of researchers has figured out precisely what happens within the brain, when it needs to learn under stress.

A team of researchers at Ruhr-University Bochum, discovered that the brain utilizes both conscious and unconscious learning mechanisms in order to compensate for the effects of stress on the brain. Specifically, this switch from completely conscious learning to subconscious learning is triggered by mineralocorticoid receptors, which are released in response to stress by the adrenal cortex.

The discovery was a result of an experiment in which 80 people participated. Of these people, 40 were given the drug, Spironolactone, which blocks the mineralocorticoid receptors from activating. The other participants were given placebos. Then, 20 participants from each group were subjected to a stressful experience.

Next, all participants engaged in a learning test in which they were shown different symbols on playing cards, and they had to learn which combinations of cards meant sunshine or rain. Some participants tried to consciously learn these combinations by creating a specific formula that would predict sunshine or rain. Others, however, relied on their "gut feeling," to unconsciously give the right answer.

Using magnetic resonance imagining (MRI), they found that the stress induced by trying to figure out the card game forced the participants' brains to switch to unconscious learning. However, those who took the mineralocorticoid receptor-blocking drug showed much less frequent use of their unconscious-learning system.

"This switch to another memory system, happens automatically," Dr. Lars Schwabe, of the Institute of Cognitive Neuroscience, said in a statement. "It makes sense for the organism to react in this manner. Thus, learning efficiency can be maintained even under stress."

The researchers say that these transitions are mediated by the amygdala, a part of the brain that's responsible for both memory and emotional reactions, and it makes sense.

Another study that looked at the effects of stress on learning had one group of participants put their hands under ice-cold water for three minutes while another group placed their hands in warm water for three minutes. Thirty minutes later, both groups were asked to memorize a list of words, which they were tested on 24 hours later.

The researchers found that men were affected by the stress induced from the ice bath more than women, as measured by cortisol levels in their blood. Because of this, they weren't able to list as many of the words as men in the warm-water group, or women in both groups. Women exposed to the ice-cold water did better than the control groups, however, the difference was small.

"Males appear to be more sensitive to stress- and cortisol-related impairments of learning and memory," Phillip R. Zoladz, co-author of the study and professor of psychology at Ohio Northern University, said.


Schwabe L, Tegenthoff M, Hoffken O, et al. Mineralocorticoid Receptor Blockade Prevents Stress-Induced Modulation of Multiple Memory Systems in the Human Brain. Biological Psychiatry. 2013.