Body & Brain

The right speed for a caress, plus the punny brain, rocking babies and more in this week’s news

Touching at the right speed
A loving caress should be nice and slow. If the speed of the stroke is too rushed, a brain region that helps the body sense pleasurable touches doesn’t respond, a new study shows. Swedish researchers scanned the brains of volunteers as a soft goat-hair brush stroked their forearm. When the brush moved at the gentle pace of 3 centimeters per second, subjects showed heightened brain activity in part of the insula, a region important for emotions. That didn’t happen when the brush moved at a quick 30 centimeters per second, the team found. The insula also responded when volunteers watched a video of a pleasantly timed social touch, the team reports in the June 29 Journal of Neuroscience. —Laura Sanders

How punny jokes tickle the brain
Jokes that rely on double entendres tickle a wide swath of the brain, a new study finds. Generally, hearing a sentence that contains a word with a double meaning activates a particular part of the brain involved in language comprehension. But in the form of a joke, double meanings have a much wider impact on the brain, English and Canadian researchers report in the June 29 Journal of Neuroscience. A joke such as “Why don’t cannibals eat clowns? Because they taste funny!” tickles the same language-comprehension brain regions as an unfunny sentence, but is also linked to activity boosts in deep brain areas that handle rewards, including the amygdala and ventral striatum. —Laura Sanders

Peer pressure on memories
A new study shows what happens in the brain as one person’s memories are shaped by another’s. Twenty healthy volunteers watched a documentary that followed police as they arrested and deported illegal immigrants. Volunteers’ initial memories of events in the film were often accurate and strong, but after researchers fed the participants false memories, volunteers changed their recollections to conform to the lies, researchers from Israel and England report in the July 1 Science. Heightened activity in a brain structure called the amygdala went hand in hand with incorrect information creeping into volunteers’ memories, brain scans revealed. —Laura Sanders

Rocking puts brain to sleep
There’s a good reason people rock babies to sleep; it works. A study in the June 21 Current Biology shows that rocking also helps adults fall asleep faster and increased the number  and frequency of some sleep-associated brain waves. Researchers from the University of Geneva put adult volunteers in an experimental hammock for a nap. The volunteers fell asleep faster when the hammock was swinging than when it stayed still. Rocking volunteers also had more sleep spindles, a type of brain wave that recent studies have suggested helps keep the brain asleep. The researchers don’t know whether rocking will help isomniacs or people with other sleep disorders. —Tina Hesman Saey

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