When children hit puberty, their ability to learn a second language drops, they find it harder to learn their way around a new location and they are worse at detecting errors in cognitive tests.

Why is this? Sheryl Smith and her colleagues at the State University of New York now reckon that all of these behavioural changes could be due to a temporary increase in a chemical receptor that inhibits brain activity in an area responsible for learning.

In 2007, Smith’s team discovered that the number of these receptors soared in mice when they hit puberty, before falling back in adulthood. In their latest study, Smith’s team set about finding out if these receptor changes in mice might lead to impaired learning abilities, rather like those seen in pubescent humans.

The group examined the hippocampus – a region known to be involved in learning – in mouse brains. Sure enough, pubertal mice had seven times as many of the receptors as infant mice. In adulthood, the number of these receptors fell back to an intermediate level. The team was also able to examine individual neurons and could see that the extra receptors were being expressed specifically at “neural projections” – sites within the hippocampus known to be involved in learning. This was further evidence that the increase in receptors might affect learning. Finally, the group measured spatial learning abilities in the mice. The creatures were placed on a rotating platform, on which a stationary section delivered a mild electric shock. After a single shock, the infant mice learnt to dodge the danger zone. The pubertal mice, however, failed to learn to avoid it even after several rounds.

Smith reckons that the same mechanism might underlie the learning deficits teenagers experience in teenagers.

Read the article to find out how this might be reversed.