If it weren't for dreams, we might not have gotten things like the double helix
structure of DNA by James Watson, the song "Yesterday" by the Beatles, or the
book "Frankenstein" by Mary Shelley. All these were products of dreams by their
authors. For thousands of years, dreams had been considered mystical, or kind of
a window into the future, or insight about the past. Ancient Egyptians believed that
dreams were like Oracles, bringing messages from the gods. In ancient China
and India, people believed that the soul was freed from the body during sleep, and
was roaming or guided until you awakened. But what does modern science have to say
about this? Do dreams really have any purpose? do they mean something? Why do we
dream in the first place? The answer is coming up right now...
A hundred years ago, it was commonly believed that we did not dream during sleep, but rather just
before we woke up. Even if the timeline within our dreams was hours, everything
happened between the few minutes between the time we were almost awake to the
time we were fully awake. Today we know that is not the case. We know for sure
now that we dream while we are asleep. So let's look at what happens in our brains
during the process of sleeping. Sleep can be divided broadly into two categories,
rapid eye movement, or REM sleep, and non REM sleep. When you fall asleep, non REM
occurs first, then you fall into REM sleep. Deep sleep actually appears to
occur in non-REM sleep, after a transition period. Just before we fall
asleep, our brain is a mess of chattering electrons with chaotic electrical waves,
before we transition to non REM sleep, where brain activity decreases. This is
also known as "slow wave" sleep. During this time, your body temperature and
heart rate fall, and your brain uses less energy. But about 90 minutes later, we go
into REM sleep, where our brain activity picks up again, and is very similar to
when we're awake. Although this is a smaller portion of
total sleep, only about 20-25%, or a total of about two hours, this is
when dreams and nightmares happen. Unlike non REM, this is associated with
fast brainwaves, eye movements, and loss of muscle tone. During REM sleep, the
brain is telling the body to move and start doing stuff just as if you are
awake. But a tiny area of the brain called the Pons causes the body to be
paralyzed. The only thing that is not paralyzed is your eyes. That's why you
have rapid eye movement, during this period. And for people that have a disorder
of the pons, sleeping can be very dangerous because they can hurt
themselves from moving around while not conscious. They can be sleepwalking. Tut
thankfully, for most people, only their eyes act out their dreams. But what is
the purpose of Dreams? One purpose appears to be to restore the brain's
energy. The brain requires a lot of energy to function when you're awake.
Although it weighs less than 3% of the body, it uses up 20% of the body's energy
when you're awake. But the brain uses significantly less energy while sleeping
than when awake. This allows the brain to build up its supply of energy in the
form of the molecule ATP, or adenosine triphosphate. And do dreams mean anything?
Sigmund Freud, the father of psychoanalysis, published his famous book,
"The interpretation of dreams" in 1899, he explained dreams as manifestations of a
person's innermost desires, or repressed childhood memories.
He believed that almost all dreams held some kind of sexual meaning. For example,
climbing stairs represents having sex. Swords, sticks, balloons and reptiles, he
believed, represented the p****. Suitcases abd chapels represent the v*****. Tearing
branches off of trees was masturbation. This was the prevailing theory for much
of the 20th century. But the theory that symbols and dreams have meaning, is
rejected by most scientists today. And much of Freud's theory has been
discredited. So if Freud was wrong, then what do dreams mean? There are a few
characteristics that all dreams seem to have in common.
#1 - we usually cannot remember them. #2 - when we do remember them, they do not
seem to make sense. #3 - they seem to trigger some
of our deepest emotions. And #4 - they seem profound. Can these
characteristics of Dreams be explained by science? Well, to a large extent they
can. During REM sleep, the part of the brain involved in logic and reason called
the prefrontal cortex, is turned off. But the emotional part of the brain, located
in the hippocampus and amygdala, are very active, more active than even when we're
awake. So this has two effects. Since our reasoning ability is not really working,
dreams don't seem to make any sense. But everything that we dream about triggers
our emotions because that part of the brain is super active. Another
physiological effect that occurs is the levels of norepinephrine decrease in the
body. This is the "fight or flight" hormone, a chemical that keeps us alert and on
our toes. It understandably goes down during sleep. But this chemical is also
involved in helping us form memories. So because it is way down during sleep, our
ability to form memories is reduced. This is why we can't remember anything.
And finally, the levels of another brain chemical called serotonin, which helps
brain cells communicate with each other, is decreased.
According to neuroscientist Dr. Robert Stickgold, this lowered level of
serotonin biases the brain to think that whatever it is experiencing is important.
So when we wake up, we think that whatever we dreamed about was somehow
profound, or holds a bigger meaning than it probably does. This feeling of the
profoundness of dreams is prevalent throughout the world and in nearly every
culture, not only today, but also can be traced back throughout our history going
back thousands of years. The culprit appears to be Serotonin, or the lack of
it. So if this profoundness is an illusion created by the chemical
activity in our brain, then why do we dream? What's the purpose of Dreams? the
question of whether dreams actually have a biological or physiological function
has not been definitively answered. But a lot of research has been done in
this area, and there is some evidence for what the answer could be. One widely held
theory is that the purpose of dreams is to help you store and build important
memories, and also get rid of or delete unimportant memories. This is similar to
defragmenting the hard drive on your computer. Your brain gets thousands, and
maybe millions of sensory inputs daily. Biologically, some of these may be
important to your survival, but most are unimportant. During sleep, it is theorized
that your brain sorts through these inputs of the day, and figures out what
to keep in long-term memory and what to delete. So REM appears important for
remembering, as well as forgetting. And experimental evidence seems to support
this because, for example, people with traumatic memories can cope better if
they get more REM sleep. It has also been shown that when people are learning new
skills, like learning a new language, dreams increase when they go to sleep.
But if dreams are just a way to defragment the hard drive of our brains,
why do some people have some of the most creative thoughts, like the structure of
DNA, or songs like Yesterday through their dreams? Scientists have proposed
that during sleep, biologically our brains are not required to focus on
survival activities. From an evolutionary perspective, our brain functions are
biased to keep us alive, to focus on things that help us eat, and avoid
predators, and danger. this bias is reduced, or gone during sleep. Researchers have
found that during REM sleep, our minds with the burden of survival being turned
off, and the logic portion of our brain in the prefrontal cortex turned off, we
can freely associate ideas and thoughts and perhaps try out different
combinations. Without the constraints of logic or survival bias, in our brain this
can allow some of the wildest and creative ideas, that would not usually
happen during waking hours, to happen. This can also allow us to see solutions
to problems that we might not consciously or logically see while awake.
So if you're stuck on something, or have writer's block, try getting some sleep.
But there's also a theory that dreams don't serve any function at all. Owen
Flanagan, Professor philosophy, at Duke University, thinks that the brain is just
firing certain sets of neurons randomly, and dreaming is just our brain vaguely
trying to make sense of it all. Could it be that it's really all just meaningless?
from a Darwinian perspective, our mental tendencies usually have some
evolutionary purpose. Dreams must have fulfilled some biological requirement
that gave us some benefit for natural selection. Otherwise we probably would
not have retained this function. According to Antti Rivonsuo, Professor at
The University of Turku in Finland, dreams prepare humans for recognizing
and avoiding danger by presenting a simulation of threatening events. This is
called the "Threat-Simulation Theory." And according to a 2012 paper written by
Ioannis Tsoukalas, PhD student at Stockholm University, REM sleep and
dreaming has evolved out of a primordial defense reflex called "tonic immobility."
This is survival by playing possum, That is, feigning death. Predators usually
don't attack animals that they think are dead. This is a common defense mechanism
in vertebrates and invertebrates. Tsoukalas thinks REM and dreaming
evolved from this evolutionary mechanism. Although there doesn't seem to be any
evidence that the content of our dreams have any profound meaning, the biological
purpose appears to be more clear-cut. Dreams help the brain function better,
and probably give us advantages in terms of creativity, problem-solving, and danger
avoidance. that being said, one 2009 study found that 56% of Americans, 65% of South
Koreans, and 74% of Indians believed that the content of their dreams provided
them with meaningful insights about their lives, and were a window into their
unconscious thoughts. So no matter what science has to say, dreams will probably
continue to fascinate, and hold special meaning for many people.