ENIKO KUBINYIBecause humans and dogs have been co-evolving for thousands of years, comparing the neurological function of the two could improve scientists’ understanding of cognition in both species. Now, researchers from Eötvös Loránd University in Budapest and the Hungarian Academy of Sciences have used functional magnetic resonance imaging (fMRI) on both humans and dogs to compare areas of the brain that respond to sounds. Their work was published in Current Biology today (February 20).
“This whole idea of comparative cognitive neuroscience has always been interesting,” said canine cognitive neuroscientist Gregory Berns of Emory University in Atlanta, Georgia, who has also used fMRI to study dogs, but did not participate in this work. “With humans, it’s always been focused on chimpanzees and other primates, so this [research] is really interesting because it’s looking at comparative anatomy and auditory processing between dogs and humans.”
The researchers used a combination of positive reinforcement techniques and social learning to train pet dogs—border collies and golden retrievers—to climb into and lie down in an fMRI scanner. They taught the dogs to stay still for five to eight minutes, which was necessary for the researchers to gather fMRI data “You might think that it’s uncomfortable for the dog, but it’s not at all,” said coauthor Attila Andics, a postdoctoral fellow at Eötvös Loránd. “The dogs just love being in the scanner,” he added.
Andics and his colleagues performed scans on 11 dogs and 22 humans while the subjects listened to nearly 300 sounds—dog vocalizations, non-verbal human vocalizations, non-vocal sounds—and silent controls. The researchers identified sound-sensitive areas in the human and canine cortices, as well as in the subcortical regions of the brain. They found that the majority (87 percent) of human auditory regions were most responsive to human vocalizations, while canine sound-sensitive brain areas were most responsive to either dog vocalizations (39 percent) or non-vocal sounds (48 percent). Vocal-processing areas were located in similar places in both dogs and people and responded most strongly to conspecific vocalizations.
“Some of the differences that they see between humans and dogs could be due to motion,” said neuroimaging specialist Gopikrishna Deshpande of Auburn University in Alabama, who did not participate in the study. He cautioned that scientists must carefully control for movement when interpreting fMRI results because even minor motion can be interpreted as activity.
Berns agreed that movement artifacts can be problematic, but noted that they did not appear to be in this case. That the researchers found the canine auditory cortex in the top part of the temporal lobe, where the primary auditory area is in most species, suggested that their technique worked, Berns said.
Andics and his colleagues also found evidence to suggest that sounds associated with positive or negative vocal emotions are processed similarly in human and canine brains. “Dogs and humans have shared a similar social environment for several thousands of years,” said Andics. “This might help explain what made vocal communication between these two species so successful or what made the alliance of these two species so effective.”
Deshpande said that the authors have made a positive case for the impact of social interactions between dogs and humans on both species’ evolution. “But what I would really like to see is another species, which did not socially evolve with humans . . . and see whether their voice selective regions are the same as a dog or not,” he said. “Only then can you make this link between the social evolution of these two species and their voice selective regions.”
“The question that I—as a scientist, as well as a dog person—want to know is: Do dogs understand any component of human language, or is it just all sounds?” said Berns. Humans have specific brain regions that process language—like Wernicke’s and Broca’s areas. “It would be remarkable to find such homologous structures in another species, especially dogs,” he added.
A. Andics et al., “Voice-sensitive regions in the dog and human brain are revealed by comparative fMRI,” Current Biology, doi:10.1016/j.cub.2014.01.058, 2014.