Equine Health Update Issue 1 Volume 16 - Page 10

SNIPPETS Horse gaits controlled by genetic mutation spread by humans From the Faroe Pony to the Spanish Mustang, fewer animals have played such a central role in human history as the horse. New research in Animal Genetics reveals that a horse’s gait, an attribute central to its importance to humans, is influenced by a genetic mutation, spread by humans across the world. The team, led by Dr. Leif Andersson from the Swedish University of Agricultural Sciences, explored the distribution of a mutation in the DMRT3 gene which affects the gait of horses, known as the ‘gait keeper.’ “All over the world, horses have been used for everyday transportation, in military settings, cattle herding and agricultural power, pulling carriages and carts, pleasure riding or racing,” said Dr. Andersson. “Over the centuries, horse populations and breeds have been shaped by humans based on the different purposes for which the animals were used.” The DMRT3 gene is central to the utility of horses to humans, as it controls a range of gaits as well as pace. From racing to pleasure riding, many species have been bred to encourage smoothness of gait. “For example, the Paso Fino is a breed from Latin America in which the frequency of the ‘gait keeper’ mutation is nearly 100%. It is claimed that the Paso Fino gait is so smooth that you can have a glass of wine in your hand without letting it spill,” said Dr. Andersson. The team analyzed 4,396 horses from 141 breeds around the world and found that the ‘gait keeper’ mutation is spread across Eurasia from Japan in the East, to the British Isles in West, on Iceland, in both South and North America, and also in breeds from South Africa. “Humans have spread this mutation across the world primarily because horses carrying this mutation are able to provide a very smooth ride, in some breeds referred to as a running walk,” said Dr. Andersson. “During such ambling gaits the horse has at least one foot on the ground that means that the vertical movement of the rider is minimal.” Human and dog brains both have dedicated ‘voice areas’ The first study to compare brain function between humans and any nonprimate animal shows that dogs have dedicated voice areas in their brains, just as 10 people do. Dog brains, like those of people, are also sensitive to acoustic cues of emotion, according to a study in the Cell Press journal Current Biology on February 20. The findings suggest that voice areas evolved at least 100 million years ago, the age of the last common ancestor of humans and dogs, the researchers say. It also offers new insight into humans’ unique connection with our best friends in the animal kingdom and helps to explain the behavioral and neural mechanisms that made this alliance so effective for tens of thousands of years. “Dogs and humans share a similar social environment,” says Attila Andics of MTA-ELTE Comparative Ethology Research Group in Hungary. “Our findings suggest that they also use similar brain mechanisms to process social information. This may support the successfulness of vocal communication between the two species.” Andics and his colleagues trained 11 dogs to lay motionless in an fMRI brain scanner. That made it possible to run the same neuroimaging experiment on both dog and human participants -- something that had never been done before. They captured both dogs’ and humans’ brain activities while the subjects listened to nearly 200 dog and human sounds, ranging from whining or crying to playful barking or laughing. The images show that dog and human brains include voice areas in similar locations. Not surprisingly, the voice area of dogs responds more strongly to other dogs while that of humans responds more strongly to other humans. The researchers also noted striking similarities in the ways the dog and human brains process emotionally loaded sounds. In both species, an area near the primary auditory cortex lit up more with happy sounds than unhappy ones. Andics says the researchers were most struck by the common response to emotion across species. There were some differences, too: in dogs, 48% of all sound-sensitive brain regions respond more strongly to sounds other than voices. That’s in contrast to humans, in which only 3% of sound-sensitive brain regions show greater response to nonvocal versus vocal sounds. The study is the first step toward understanding how • Equine Health Update •