Dogs' Brains Reorganized by Breeding 

 (Very interesting read. It seems as if the changes in the position of the brain may have altered the dogs sense of smell, especially in some breeds more than others) ​

For thousands of years humans have changed the sizes, shapes, colors, and coats of dogs through selective breeding. Now it seems we've actually reordered many breeds' brains in the process.

A new brain-imaging study examined 11 carcasses from 11 different dog breeds, both long-snouted, such as the greyhound and Jack Russell terrier, and short-snouted, such as the mastiff and pug.

The team found that the brains of many short-snouted breeds have rotated forward by as much as 15 degrees.

Furthermore, in these breeds the brain region for smell, called the olfactory bulb, has drifted downward toward the base of the skull, perhaps significantly altering the dogs' all-important source of smell, researchers say.

Since the first wolf was domesticated an estimated 12,000 years ago, "selective breeding has produced a lot of [anatomical] variation, but probably the most dramatic is in terms of skull shape," said study co-author Michael Valenzuela, a neuroscientist at the University of New South Wales in Australia.

"Dogs are very unique in having such a massive diversity of skull shapes," Valenzuela added, "more than any other species really."

Dog Brain Changes Equal Changed Behavior?

It's unclear whether the brain rotation and olfactory bulb movement of short-snouted, or brachycephalic, dogs has affected their ability to smell, but Valenzuela and his colleagues note that short-snouted dogs are usually not used for scent work.

"We think of dogs living in a world of smell—but this finding strongly suggests that one dog's world of smell may be very different to another's," study co-author Paul McGreevy of the University of Sydney said in a statement.

One way the brain changes could have changed the dogs' olfactory sense is by affecting a pathway in the brain called the rostral migratory stream, or RMS, the team speculates. Other studies have suggested the RMS is important for a normal sense of smell.

"The RMS starts very deep in the middle......READ MORE

Ker Than

for National Geographic News

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