Did you ever wonder what’s happening in your dog’s brain while they’re napping? A group of Hungarian researchers say your four-legged friend may be learning. Their study, published in Scientific Reports on Oct. 11, looked at dogs’ brain activity during sleep and found patterns, similar to patterns seen in humans, indicating the dogs’ brains were sorting and storing new information. Dogs’ brain waves have been observed before, but this is the first time these particular patterns have been analyzed in relation to their function. The results suggest dogs could be used as models to help us better understand similar brain wave patterns in humans.
The researchers worked with 15 pet dogs divided into two groups, and held a training session where they taught both groups of dogs to perform two familiar actions: sit and lie down. The first group was taught in English and Hungarian, while the second group was taught solely in Hungarian. The first group of dogs responded to the English commands instead of the Hungarian commands they already knew, while in the training session for the other group of dogs, the researchers used only Hungarian commands. The scientists swapped the types of training sessions the groups received on the second research day and switched them back on a third day. After each training session, the dogs were allowed to sleep for three hours while their brainwaves were recorded as electroencephalograms (EEGs). Once the dogs were allowed to nap, those that had received training with English commands were given the new commands again to test their learning.
The researchers looked for patterns called sleep spindles in the EEGs; sleep spindles represent bursts of brain activity during non-REM sleep, which last between half a second and five seconds and occur in the nine to sixteen Hertz range in humans. Previous studies in both humans and rats have associated sleep spindles with the sorting and storage of new information, a process known as memory consolidation.
The researchers found the density of sleep spindles, defined as the number of spindles per minute, in the nine to sixteen Hertz range was significantly higher when the dogs were taught English commands than when the dogs performed the already known Hungarian commands. Furthermore, the researchers found the density of sleep spindles was positively correlated with the dogs’ ability to follow the new commands after their naps. Ultimately, the greater the density of a dog’s sleep spindles, the more likely they were to correctly follow an English command after sleeping, suggesting that sleep spindles play a role in memory consolidation in dogs, similar to the role they play in humans.
Researchers also found a significantly greater density of sleep spindles in female dogs than in male dogs, and when taught English commands the females responded correctly to the new commands after sleeping more frequently than the males. This result reflects human studies which observed greater numbers of sleep spindles in women than in men. The researchers also looked for differences in sleep spindles in the dogs due to age, as compared to human studies showing amplitude and density of sleep spindles decreasing with age, while frequency rises. The researchers could not establish a definite correlation between sleep spindles and age in the dogs they studied; however, they suggest this ambiguity could be resolved by larger studies.
The researchers divided the observed spindles into two groups: slow spindles— those occurring at less than 13 Hertz, and fast spindles— those occurring at more than 13 Hertz. A distinction was also established in human studies. Female dogs showed a greater density of both slow and fast spindles, however, only density of slow spindles maintained a correlation with the dogs’ correct performance of new commands. This is in line with what researchers expected because slow spindles occur in the frontal area of the brain, which is associated with verbal memory in humans. Since the dogs were following verbal commands, activity in this region would make sense if their brains processed new verbal information similarly to humans.
This study supports the argument that dogs could be used as models to help us better understand sleep spindles in humans. Additionally, because sleep spindles are altered by certain diseases, the research could be used to advance the diagnostic use of EEGs by veterinarians.
What practical advice can dog owners take from the study? If you’re trying to teach your pet a few new tricks, don’t interrupt their nap!
Abbey Bigler is a fourth-year English major with minors in business and technical writing, communication studies and biology. She can be reached at AB842693@wcupa.edu.