Study finds brain changes during sleep

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PALO ALTO, Calif., Oct. 7 (UPI) -- The number of connections, or synapses, in a particular region of the brain varies between night and day and appears to be regulated by a gene, researchers say.

Stanford University scientists have been studying what happens in the brain while you sleep and how the circadian clock and sleep affect neuron-to-neuron connections, a university release says.

Why we need to sleep and how, exactly, sleep is restorative are unanswered questions in biology.

Using zebrafish, a popular aquarium fish that, like humans, are active during the day and sleep at night, they studied "synaptic plasticity," the ability of synapses to change strength and even form and erase.

"This is the first time differences in the number of synapses between day and night and between wake and sleep have been shown in a living animal," researcher Lior Appelbaum, said.

They theorize that nighttime changes in the number and strength of synapses -- the synaptic plasticity -- help recharge the brain and, in turn, benefits memory, learning and other functions.

"It gets ready for new activity by telling the neurons they have to shut down synapses during this time of day but increase them at other times of the day," he said.

They also identified a gene that appears to be involved in regulating the rhythmic changes in synapses.