New findings support a controversial hypothesis about the biological role of sleep: Snoozing may be a way for the brain to clear clutter accumulated after a hard day of synapse forming and strengthening. Two __Science__ studies published today suggest that the brains of sleeping __Drosophila__ undergo an overall depression in synaptic strength and number, eliminating some minor neuronal connections while merely weakening stronger ones.
Expression of synaptic markers is low after
sleep (left) and high after waking (right)
in most regions of the fly brain

Image courtesy of
Chiara Cirelli
"Essentially you're reducing the signal to noise ratio," linkurl:Paul Shaw,; a Washington University neurobiologist and lead author on one of the papers, told __The Scientist__. The hypothesis was first proposed about five years ago by linkurl:Chiara Cirelli; and linkurl:Giulio Tononi,; neurobiologists based at the University of Wisconsin-Madison and coauthors on the other __Science__ paper. (You can read more about their...
Shaw's team found newly-formed
synapses in the brains of fruit fly's
kept in a stimulus rich environment.
The cells are highlighted on the
upper right side of the image.

Image courtesy of Washington University
School of Medicine

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