A US team of scientists have made a fresh breakthrough in the case of the first night effect - a phenomenon where people find it difficult to sleep under a new roof, and often wake up the next day all tired and groggy.
The research said when we stay somewhere new, our brains seem to spend the first night in surveillance mode. While one hemisphere goes to sleep, the other half of the brain remains on night watch. Masako Tamaki, a sleep scientist at Brown University in Providence, said, “If we don't know whether a room is safe to sleep in, then we will have this night watch system so we can detect anything unusual. It's like a safeguard.”
The team of sleep scientists used magnetoencephalography (MEG), structural MRI and polysomnography, a combination of muscle tone and other measurements, to monitor how 35 people slept in the laboratory. The scientists are not sure whether the left hand side of the brain is always more alert during the first night effect. They recorded brain activity for only 90 minutes as people slept, so it is possible that, like the dolphin, the brain switches its night watch system from one side to the other while the person sleeps. “There’s certainly a possibility that the vigilant hemisphere changes over the night,” Tamaki said.
If the findings are confirmed with further studies, this effect might be the human equivalent of birds sleeping with one eye open, and one half of the brain awake, to ensure they are not eaten by night time predators.
The findings could shed light on an issue that comes up with some insomniacs who are studied in sleep research centres. Patients may say they did not sleep all night, when EEG recordings of their brain activity suggest that they did. “If you do high density EEG, you can sometimes see signs of arousal in some brain areas of these patients,” said Dijk. “So this finding adds to the data that sleep is not a complete global phenomena, there are local aspects to it. The brain can be locally awake, and maybe this is maybe what is happening in the first night effect.”
