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Slice of Science: Ringing heads, Cracking knuckles, Puppy emotions

What causes a concussion?

Between 1.6 and 3.8 million sports and recreation-related concussions are estimated to occur in the United States each year, however scientists remain unsure of how a blow to the head produces the symptoms. New research suggests that concussions originate not necessarily from the collision of the brain with the skull, but likely in the stretching and tearing of tissue that "ringing" causes deep within the brain. The study, utilizing a new modeling technique, finds that this ringing is a result of the brain oscillating at different frequencies, similar to a real bell. New research implies new safety standards: researchers suggest that better helmets could be designed to dampen the most damaging low-frequency vibrations.

Pop goes your knuckle!

But what makes the sound? Scientists have struggled to discern an answer because the "cracking" all happens so fast; instead they now to mathematical formulas. They tested a popular theory: bubbles form in a fluid-filled space between the finger and hand bones, and when the joint expands during the act of knuckle-cracking, the subsequent collapse of those bubbles causes the popping sound. The model indeed confirmed that "mathematical" bubbles in the knuckle joint generated sound waves that look just like the ones created in real life. Blame it on the bubble!

"Yeah, I feel you," says Fido

Any dog lover will tell you that our canine friends are good at reading faces, able to discern between emotions such as happiness and anger. Scientists know that, like humans, dogs watch the left side of people's faces, where emotions first appear. However, what neural mechanisms underlie this ability? To find out, researchers trained eight border collies to lie still in a fMRI scanner, and presented them with photos of humans' either happy or neutral expressions. Results showed that a happy human face produces a distinctive signature in a dog's temporal lobe and other neural regions. Researchers summarize "human emotions are specifically represented in dogs' brains, highlighting their importance for interspecies communication."

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