david 发表于 2019-9-10 14:30:55 | 显示全部楼层 |阅读模式
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Dogs are a weird bunch. They range in size from bearish behemoths like Newfoundlands to pipsqueaks like Milly, a Chihuahua who measures less than four inches tall and holds the Guinness record for World's Shortest Dog.


Some breeds are fast runners. Others are jumpers, swimmers or diggers. Bloodhounds specialize in sniffing, while greyhounds hunt primarily by sight. Border collies excel at herding, Jack Russell terriers at flushing foxes from dens.


Over at least 15,000 years, and especially since a Victorian-era dog-creation craze, selective breeding by humans has resulted in a single species with more physical variation than almost any other in the animal kingdom.


And now, scientists have provided the first evidence that all of this selective tweaking hasn't just changed dogs' sizes, shapes, colors and behaviors - it's also altered the way their brains are built.


Their research, published Monday in The Journal of Neuroscience, began with MRI scans from 62 dogs that had visited the University of Georgia Veterinary Teaching Hospital for neurological evaluations. All the dogs, representing 33 breeds, were discharged with clean bills of brain health. But their scans provided the scientists with a treasure trove of data.

他们的研究发表在周一的《神经科学杂志》(journal of neuroscience)上,首先对62只狗进行核磁共振扫描,这些狗曾到佐治亚大学兽医教学医院进行神经系统评估。所有的狗,代表33个品种,出院时大脑健康状况良好。但他们的扫描为科学家们提供了大量的数据。

"The first question we wanted to ask was, are the brains of different breeds of dogs different?" said Erin Hecht, a neuroscientist studying dog cognition at Harvard University and lead author of the study.


Indeed, from Dachshunds to Dobermans, the scientists found well-defined differences between dog brains, even after accounting for things such as the pooches' overall size and shape.


By looking at the areas of the dogs' brains that varied most across the breeds, the scientists were able to create maps of six neural networks linked to certain functions, such as the sense of smell or movement. The team found the shape of these networks "correlated significantly" with common traits associated with each breed, as described by the American Kennel Club.


"Brain anatomy varies across dog breeds," Hecht said, "and it appears that at least some of this variation is due to selective breeding for particular behaviors like hunting, herding and guarding."


In other words, not only do the shapes and sizes of canine brains vary by breed, the structures within those brains also are different. This discovery helps explain what makes a Maltese act like a Maltese, or a boxer like a boxer.


Jeffrey Stevens, director of the Canine Cognition and Human Interaction Lab at the University of Nebraska at Lincoln, called the study's use of existing MRI data "clever" and its premise "exciting." However, he offered some words of caution.

林肯内布拉斯加州大学犬类认知与人类互动实验室主任杰弗里·史蒂文斯(jeffrey stevens)称,这项研究利用现有的核磁共振数据是“聪明的”,其前提是“令人兴奋的”。不过,他也提出了一些警告。

"The one thing that I think there's a bit of disagreement on in the literature and in people's views is how useful it is to map behaviors to breeds," Stevens said. "There's often a lot of variation within a breed, across individuals."


Stevens also noted the MRI scans weren't performed as the dogs were performing breed-specific tasks, making it difficult to draw big conclusions linking breed to behavior.


"This is very well known in the human neuroimaging field, where you want to be really careful drawing any inferences about cognitive processes that are based on brain activity that you're not directly testing," Stevens said.


But this raises another intriguing question. Most dogs today do not actively fill the roles for which their breed was created.


In fact, all 63 study dogs were house pets, not working dogs. So even though they may be the descendants of great herders or hunters, they probably don't perform those tasks in any serious capacity. That could make a big difference.


"It's not like [your brain] gets a new wrinkle every time you learn something," Hecht said. "But there have been lots of studies that show your brain changes as you learn a new language or as you learn a new motor skill."


So it's quite possible that a Labrador retriever that does the job its kind was bred to do - retrieving birds shot by hunters - might have a brain that looks different from a Lab that retrieves popcorn stuck between couch cushions.


Stevens said he viewed this as a hint that the researchers might be onto something. If they've managed to find such significant variation in pets, he said, imagine what might be discovered in the brains of working dogs.


"The correlations actually could be stronger if you used animals that were still bred for those purposes," Stevens said.


Daniel Horschler, a PhD student at the University of Arizona's Canine Cognition Center, said the variation found across dog breeds could prove to be an important model for understanding how brains work in general.


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