When someone has to learn new knowledge under stress, the brain uses unconscious rather than conscious learning processes. Now, neuroscience researchers at the Ruhr-Universität in Germany have found out that the switch from conscious to unconscious learning systems is triggered by the functioning of mineralocorticoid receptors.
The receptors are activated by stress hormones released by the adrenal cortex. Mineralocorticoids are a class of steroid hormones characterized by their influence on salt and water balances.
The team examined 80 subjects; 40 were given a drug blocking mineralocorticoid receptors in the brain. The other 40 participants were given a placebo drug. Twenty participants from each group were subjected to a stress-inducing experience.
Weather Prediction Test
After the stressful experience, all the participants took a learning test, the so-called weather prediction task. The subjects were shown playing cards with different symbols and had to learn which combinations of cards meant rain and which meant sunshine. The researchers used MRI to record the respective brain activity.
There were two different approaches to the weather prediction test. Some subjects tried consciously to formulate a rule that would enable them to predict sunshine and rain. Others learned unconsciously to give the right answer, winging it in other words.
The same research team had demonstrated in August 2012 that, under stress, the brain prefers unconscious to conscious learning.
“This switch to another memory system happens automatically,” says Dr. Lars Schwabe, lead author. “It makes sense for the organism to react in this manner. Thus, learning efficiency can be maintained even under stress.”
Mineralocorticoid Receptors Viral Role
However, the unconscious method works only with fully functional mineralocorticoid receptors. When researchers blocked these receptors by applying the drug Spironolactone, the participants switched over to the unconscious strategy less frequently, thus demonstrating a poorer learning efficiency.
The effects were also seen in MRI data. Normally, stress makes brain activity shift from the hippocampus, an area of conscious learning, to the dorsal striatum, which manages unconscious learning. However, this stress-induced switch took place only in the placebo group, not in subjects who had been given the mineralocorticoid receptor blocker.
It stands to reason then, the mineralocorticoid receptors play a crucial role in enabling the brain to adapt to stressful situations.
L. Schwabe, M. Tegenthoff, O. Höffken, O.T. Wolf (2013): Mineralcorticoid receptor blockade prevents stress-induced modulation of multiple memory systems in the human brain,
Biological Psychiatry, DOI: 10.1016/j.biopsych.2013.06.001