Brain waves common during sleep also show up in awake sheep

If humans have similar ‘wake’ spindles, they may play a daytime role in holding onto memories


Sleeping sheep have brain bursts called spindles that, in people, are thought to help solidify memories. Spindles also flicker in the brains of awake sheep, a new study finds.

Jacobo Hernández/agefotostock/Alamy Stock Photo

Here’s something neat about sleeping sheep: Their brains have fast zags of neural activity, similar to those found in sleeping people.

Here’s something even neater: These bursts zip inside awake sheep’s brains, too. These spindles haven’t been spotted in healthy, awake people’s brains. But the sheep findings, published March 2 in eNeuro, raise that possibility.

The purpose of sleep spindles, which look like jagged bursts of electrical activity on an electroencephalogram, isn’t settled. One idea is that these bursts help lock new memories into the brain during sleep. Daytime ripples, if they exist in people, might be doing something similar during periods of wakefulness, the researchers speculate.

Jenny Morton, a neurobiologist at the University of Cambridge, and her colleagues studied six female merino sheep with implanted electrodes that spanned their brains. The team collected electrical patterns that emerged over two nights and a day. As the sheep slept, sleep spindles raced across their brains. These spindles are akin to those in people during non-REM sleep, which accounts for the bulk of an adult’s sleeping night (SN: 8/10/10).

But the electrodes also caught spindles during the day, when the sheep were clearly awake. These “wake” spindles “looked different from those we saw at night,” Morton says, with different densities, for instance. Overall, these spindles were also less abundant and more localized, captured at single, unpredictable spots in the sheep’s brains.

As to the job of these daytime bursts, “I have no idea,” Morton says. But the results hint that these spindles may somehow help the brain handle certain kinds of information during the day, not just at night.

In humans, changes in sleep spindles have been linked to aging, as well as diseases including Alzheimer’s, Parkinson’s and Huntington’s. Studying these spindles over time in sheep may reveal clues about these human disorders, the researchers suspect.

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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