What do animals dream about?
//Summary - Level-C2//
As historical and modern research indicates, animals likely experience dreams akin to humans. Aristotle observed dreaming in various animals, and contemporary studies show physical and neurological signs during sleep that suggest dreaming. Techniques like monitoring animals' brain activity and physical movements during REM sleep have provided evidence that animals replay waking experiences while asleep, albeit the subjective experience of these dreams remains unknown.
//Summary - Level-A2//
Jason G. Goldman discusses how animals might dream, beginning with observations from Aristotle, who believed that animals like horses and dogs also dream. Modern science examines animal dreams by studying their sleep behaviours and brain activity, showing similarities to humans. Experiments have shown that animals exhibit dream-like activities, such as cats displaying hunting behaviours and zebra finches seeming to practice songs in their sleep. Understanding animal dreams combines observations of physical behaviours and brain functions during sleep.
A)
If animals dream like us, where do they go in their slumber? Jason G Goldman explores how we can peer into the minds of sleeping cats, birds and other creatures.
"Almost all other animals, whether aquatic, airborne or terrestrial, are observed to participate in sleep," wrote Aristotle in his work On Sleep and Sleeplessness. But do other animals dream? The Greek philosopher also had an opinion on this.
In The History of Animals, he wrote: "It seems that not only men dream, but also horses, dogs, and oxen; yea, and sheep, and goats, and all viviparous quadrupeds; and dogs show their dreaming by barking in their sleep. His research methods may have lacked sophistication, but Aristotle may not have been too far off the mark.
We certainly can't ask animals if they dream, but we can at least observe the evidence that they might. Scientists have approached this seemingly impossible task in two ways. One is to look at their physical behaviour during the various sleep cycle stages. The second is to see if their sleeping brains work similarly to our sleeping brains.
The story of how we figured out how to look into the minds of sleeping animals began in the 1960s. At that time, anecdotal reports started to appear in medical journals describing people making movements in their dreams. This was strange because our muscles are typically paralysed during REM sleep (rapid eye movement).
B)
Researchers realised they could study how animals dream by inducing a similar state. In 1965, French scientists Michel Jouvet and J.F. Delorme found that removing a part of the brain stem called the pons from a cat's brain prevented it from becoming paralysed during REM sleep. The researchers called this condition "REM without atonia" or REM-A. Instead of lying still, the cats paced and behaved aggressively.
This suggested that they were dreaming about activities from their waking hours. Since then, studies have found similar behaviours. According to veterinary neurologist Adrian Morrison, who has written a review of this research, cats in REM-A move their heads as if following stimuli. Some cats also behave identically to predatory attacks, as if chasing mice in their dreams. Similar dream activity has been observed in dogs.
C)
Some humans have also been found to 'act out' their dreams - if they suffer from a condition called REM sleep behaviour disorder. "Punching, kicking, jumping, and running out of bed during attempted dream enactment are common manifestations and usually correlate with reported imagery," according to the International Classification of Sleep Disorders (ICSD). Injury is common among these people and those who sleep with them, the ICSD adds.
D)
Physical movement is not the only way to peer into dreams. Researchers can now peer humanely into the electrical and chemical activity of brain cells in animals as they sleep. In 2007, MIT scientists Kenway Louise and Matthew Wilson recorded the activity of neurons in a part of the rat brain called the hippocampus, a structure involved in memory formation and encoding. They first recorded the activity of these brain cells while the rats ran in their mazes.
They then looked at the activity of the same neurons while the rats slept. Louise and Wilson discovered identical patterns of firing during running and REM sleep. In other words, it was as if the rats were running the maze in their heads while they slept. The results were so precise that the researchers could deduce the exact location of the rats in their mental dream maze and map it to actual locations in the real maze.
E)
Biologists at the University of Chicago, Amish Dave and Daniel Margoliash, looked into the brains of zebra finches and discovered something similar. These birds are not born with the melodies of their songs hard-wired into their brains; instead, they must learn to sing.
When awake, neurons in a part of the finches' forebrain called the robutus archistriatalis fire after they sing specific notes. The researchers can determine which note was sung from the firing patterns of these neurons. By piecing together the electrical patterns in these neurons over time, Dave and Margoliash can reconstruct the entire song from beginning to end.
Later, when the birds were asleep, Dave and Margoliash looked again at the electrical activity in this part of their brains. The neurons weren't firing at random. Instead, the neurons fired in sequence, as if the bird were singing the song note by note. You could say that the zebra finches were practising their songs as they slept.
F)
Can the behaviour of cats in scientific experiments be described as dreaming? Do rats have any subjective awareness that they're doing their mazes in their heads while they're napping? Are songbirds aware that they're singing in their sleep? These questions are as challenging to answer as the question of consciousness. It's tricky.
We humans don't usually realise we're dreaming while we're dreaming, but it becomes apparent as soon as we wake up. Do zebra finches remember their dreams as dreams when shaken out of their sleep? Can they distinguish the natural world from the world of their dreams?
We can say with reasonable certainty that the physiological and behavioural features of dreaming in humans have now been observed in cats, rats, birds and other animals. But what it's like to dream when you're not human remains a mystery.
What do animals dream about?
https://www.bbc.com/future/article/20140425-what-do-animals-dream-about
After waking up from a scary dream, the cat's reaction was so cute!
youtube.com/watch?v=eoLcYpaAfMk
