London, April 14 (Inditop) A developing foetus can enter a dream sleep-like state weeks before the first rapid eye movements are seen, according to a discovery by neuroscientists and mathematicians.
The first rapid eye movements are discernible during the seventh month of foetal development. The brain of the developing embryo appears to alternate every 20 to 40 minutes between REM sleep, in which brain activity rivals that of consciousness, and non-REM sleep, in which the brain rests.
Directly measuring the brain activity of a human foetus is impossible. What we know about our early sleep habits comes mostly from watching eye movements.
Some have tried to measure the brain activity of premature babies by hooking them up to an electroencephogram (EEG) after they are born early.
These measurements, according to mathematician Karin Schwab, are technically difficult and fraught with errors. So neurologists who study the development of the foetal brain do not know whether sleep cycles simply appear one day, or whether they develop slowly from other forms of brain activity.
Accordingly, Schwab of Friedrich Schiller University in Jena, Germany, studied sheep, an animal that typically carries one or two foetuses similar in size and weight to a human foetus.
They recorded electrical activity in the brain of a 106-day-old developing sheep foetus directly – something that had never been done before.
Besides, the course of brain development is also fairly similar in humans and sheep, lasting about 280 and 150 days, respectively.
Using sophisticated mathematical techniques, Schwab discovered cycles in the complexity of immature brain activity. Unlike sleep patterns in later stages of development, these cycles fluctuate every five to 10 minutes and change slowly as the foetus grows.
While it is difficult to imagine what the foetus experiences during these cycles in terms familiar to adults, the patterns shed new light on the origins of sleep, said a Friedrich Schiller release.
“Sleep does not suddenly evolve from a resting brain. Sleep and sleep state changes are active regulated processes,” said Schwab. The finding fits with other data showing that the brain cells (neurons) that generate sleep states, mature long before the rest of the brain is developed enough to fall into REM sleep.
A better understanding of brain development could provide clues about diseases later in life, like neurological disorders or crib death. The research may also shed light on fundamental questions about how the brain develops.
The research appeared in a special focus issue of Chaos, published by the American Institute of Physics (AIP).
