Authors: Louise White
In a new study recently published in Science Advances, a team of researchers from Washington State University Spokane (WA, USA) were able to document the effects of sleep on vision development in young animals. The findings, which highlighted the importance of rapid eye movement (REM) sleep for consolidating changes in brain circuits, help to extend current understanding of children’s sleep requirements but also bring into question the increasing use of REM-disrupting medications.
Despite it being known that the amount of REM sleep is higher during the perinatal period compared to in adulthood, prior to the study little was understood about the importance of REM sleep for young brain development. The researchers discovered that the activation of ERK, an enzyme that is stimulated only during REM sleep, enables the brain to consolidate changes in the visual cortex that occur in response to new experiences.
Using cats as the test subject, the team of researchers were able to show that REM sleep is required in order to promote ocular dominance plasticity. During the experiments, patches were placed over one eye of each of the young animals and their brain activity was monitored both while awake and while asleep. In order to measure the effect of REM sleep, the cats were individually housed in a recording chamber, the floor of which was made up of a motorized platform that could be activated to awaken the animal intermittently during REM sleep. Another group of cats were subjected to fragmented sleep, but instead were awakened during non-REM sleep. A final group was allowed completely undisturbed sleep.
Cats with undisturbed sleep exhibited shifts in ocular dominance plasticity following monocular deprivation, as expected. This effect was reduced in the group subjected to REM sleep deprivation, and in which consequently normal vision did not develop. Shifts in ocular dominance plasticity were again preserved in the group subjected to non-REM fragmented sleep, illustrating that it was the disruption of REM sleep that was responsible for the non-preservation of cortical changes. In addition to this ERK was not activated, meaning brain changes could not be solidified.
“The visual cortex is very sensitive to information it is receiving and there are critical periods for its development,” explained lead author, Marcos Frank (Washington State University Spokane).
“There is a lot of data accumulating that says the amount of sleep a child gets impacts his/her ability to do well in school. This study helps explain why this might be – and why we should be cautious about restricting sleep in our children,” he added.
Frank finished by highlighting the increasing prescription of drugs that disrupt brain activity earlier in life by pediatricians: “The fact is, we have very little pre-clinical research data to tell us what these drugs are doing to developing brains in both the short and long term.”
Sources: Bridi MCD, Aton SJ, Seibt J, Renouard L, Coleman T, Frank, MG. Rapid eye movement sleep promotes cortical plasticity in the developing brain. Science Advances, 1(6), e1500105 (2015); Washington State University press release