A sleep study that
records brain waves is called polysomnography. When conducted on dogs, it shows
that dogs actually have similar sleep and dream patterns as you do. Myoclonus
is involuntary muscle twitching that both humans and dogs do, most often while
sleeping. Almost all studied animals exhibit signs of myoclonic twitches,
especially infant animals such as puppies. Like humans, dogs cycle through
sleep cycles with periods of wakefulness, deep rapid-eye-movement (REM) and
non-rapid-eye-movement or slow-wave-sleep (SWS). As he first falls asleep your
dog enters into SWS, where his mind goes to sleep. Muscle tone remains but
mental processes are shut down in SWS. This is a transitional state, so it is a
lighter sleep and the muscles are not completely relaxed. Your dog will appear
at rest and calm in SWS. REM sleep, however, produces brain waves that are
irregular and rapid and testing shows dogs have heightened senses of mental
activity. It is during the REM phase that your dog will most likely move in his
sleep, whine, breathe rapidly or even bark. You may also see his eyes moving
back and forth behind his lids and at times his eyes may even be slightly open.
When humans are awoken during REM sleep, they often report they are dreaming
and the same is most likely true for dogs.
Typically, dogs spend roughly twelve
percent of their sleeping time in REM sleep. Puppies and elderly dogs spend
more. Theorists believe puppies need that time to deal with all of their newly
learned information. Elderly dogs have aging mental processes so theoretically
it takes longer for them to process their thoughts thus spending more time in
REM to do so. Another theory for more physically active sleep in elderly dogs
and puppies is that the part of the brain that inhibits large muscle groups
during sleep, called the pons, is less efficient in elderly dogs and not fully
developed in puppies. Also worth noting is that for reasons that have yet to be
discovered, the size of your dog also determines his dream cycles. Larger dogs have longer dreams but they are
less frequent while smaller dogs have shorter dream cycles that are more
frequent.