If I had to guess what my dogs dream about when they enter the REM (rapid eye movement) phase of sleep, the images would certainly include squirrels, a peanut-butter filled KONG, and the flash of weeds as they tear along their favorite trail. Most of us have witnessed the tell-tale eye twitches and running motion of recumbent legs that signal dreaming in our pets. Typically, a medium-sized dog will begin to dream about 20 minutes after falling asleep; their breathing may become shallower and irregular as compared to deep, sonorous, non-dreaming sleep. The darting of eyes behind closed lids is the dog “seeing” images as if they were viewed in real life. Some animals may even snap or growl at imagined prey. Humans awakened during this same phase of sleep report they were dreaming at the time. 1
How do we know what is happening in our pets’ minds as they sleep? Anecdotal and scientific research both indicate the probability and content of a dream state. Anatomically and physiologically, the animal brain is extremely similar to a human’s, who we know dream of events and images pulled from daily life. Of special importance in the generation of dreams is the hippocampus, an area of the brain associated with memory formation and storage. In rats, a species with a simpler brain structure, electrical recordings were taken from the hippocampus while the rats were awake and completing a complex maze. The brain waves generated by these rats running the maze were very specific, repeatable, and so precise that researchers could pinpoint which area of the maze the rats were running based on the electrical wave. Later, when brain activity had indicated the rats were in the dream-generating REM portion of sleep, MIT scientists observed these identical waves. This data was extrapolated to mean that the rats were dreaming about the maze they had just completed, down to precise location of the maze the rats were “running” in sleep. 2 In all likelihood, our pets are dreaming about their version of the maze, dashing along a familiar path or playing with a favorite squeaky toy of which the hippocampus has retained images.
Another portion of the brain, the pons, was studied to determine dream content. In addition to acting as a sensory message relay center in the brain and helping to regulate sleep and respiration, the pons helps hinder movement in sleep. Without this special structure, animals actively engage in movement in the same manner during sleep as they would when awake. In studies where the pons was removed or inactivated, sleeping dogs executed familiar actions even when brain waves indicated they were dreaming, such as chasing make-believe balls and flushing out imagined birds. Observing this study sounds like watching a dog zombie apocalypse! Puppies, kittens, human babies, and seniors all experience more movement such as twitching during sleep due to the underdeveloped or less efficient pons. 3 Fascinating!
If pets dream about their daily lives, can they also have nightmares of being home alone during a storm or being attacked by another animal? If it occurred in real life, it’s very likely they do. 4 It can be difficult to watch your restless friend dream and become agitated in sleep. Should you wake them from their nightmare or leave them be? From personal experience, it can be very disorienting having a scary dream interrupted by the alarm clock; it takes a few minutes for my breathing to slow and my mind to register my surroundings. Instinctually, your pet may react aggressively and unpredictably if woken during a nightmare. It’s best to let them sleep though it; when they wake, provide plenty of playtime and snuggle time to create joyful memories!
Dr. Lisa McIntyre