A short overview of dream science

Definition: mental activity occuring in sleep.

Duh? The above defintions seems a no-brainer, because it's so general and wide. Wwhat type of mental activity do they mean for example?

TYPES OF MENTAL ACTIVITY

1. illusionary internal bodily sensations as you just have fallen asleep: for example you can feel as if paralyzed and unable to move, or slowly gliding down as if into water, or as if falling and have a jerking reaction (waking you up too). None of these are accompanied with images. Some of this may be caused by  the physical activities during the day, like going out on a boat trip for example. 
2. pure thoughts: you have an exam the next day, and fall asleep still thinking of it, and your sleep gives you no escape from these thoughts. They go on and on, often waking you up early in the night. Aside from thoughts the only thing accompanying it are emotions. 
3. visual plots: this is what we often associate with dreams. It's a full blown story, with images, events, dramatic, comples, bizarre, hallucinatory. You live in a house that you accept to be your house, but in reality your house is somewhere else and looks different. Your friends are there, but don't actually look as they do in real life. First you are at one place, and next you are someplace different without pre-warnings of the change of scenery. You do things you never even imagined doing, or might not even be possible in real life. And you encounter creatures you would never believe to exist. You have conversations, hear phones ring, run, touch things - all your sensitory neurons are active and sensing a physical world that simply does not exist. And lastly your emotions are alive almost constantly. Despite its total lack of logic and coherency, despite it contradicting reality, you accept the events and experiences as normal, until you wake up.

The first two are obviously related to daytime experiences, or effects of the body and mind falling asleep. But the last one is a whole different ballgame. Obviously it is the most active one, and thus the brain must be more active than during the previous two. And yet we would expect that if our brain is more active we would be more coherent, that details would be more exact and that we act more logically. But we do not.

So, what is going on then? As it turns out, chemical changes in the brain and selective brain deactivation enhance and shut down certain mental functions.

EVERYBODY DREAMS

Everybody's brain ever studied while asleep is active during sleep, and are accompanied by rapid eye movement (hence REM sleep). When the subjects were awakened during these REM-sleep phases on average 82% of the people reported they had been dreaming. This is why scientists assume everybody dreams. If you think you do not dream, then this is attributed to the not being able to recall your dreams. When people sleep through the REM-sleep, and do not wake up at the moment of dreaming (if only for a few seconds), it is very hard on anyone to ever recall them. Even when you recall dreaming as you wake up, the dream often soon fades into forgetfulness.

The reason why it is so hard to recall a dream is because the chemical systems responsible for recent memory get turned off during sleep brain activity. In other words, your short term memory gets shut down, and unless you wake up which will reactivate the short term memory you will not remember your dream. 


WHEN IN OUR SLEEP DO WE DREAM

Previously it was thought that we only dream during the REM-sleep. However, the dreamlike state and dream has been shown to occur during sleep-onset and NREM-sleep as well as REM sleep. Sleep-onset shows type 1 mental activity. Non-REM sleep or low wave sleep early on in the night can include type 2 mental activity, whereas type 3  (the most active of the 3) typically occurs during REM-sleep.And while the REM-sleep dreams are more vivid and have more emotional impact, we dream as much dreams during NREM than during REM sleep. We go through four sleep cycles alternating NREM-sleep with REM-sleep. NREM-sleep typically belongs to stage 3 and stage 4 of the drop in brain activity. In total we go through 4-6 dreams in eight hours of sleep, with each sleep cycle taking approximately 90 minutes. So, we basically dream throughout the whole of the night. Only the type of dreams will differ.

Sleep Cycle chart

Most body activity lowers to the minimum in a stage 4 NREM-sleep and it will be hard to wake us. During REM-sleep there is a lot of small facial movement, eye movement, faster pulse and breathing, and yet we are unable to move, but easily woken up.

WHAT PART OF THE BRAIN IS ACTIVE

During NREM-sleep the lower half of the brainstem connected to the spinal cord regulates autonomic functions of our body: breathing, blood pressure and swallowing. In other words, while everything of our body gets a rest, de medulla makes sure we function minimally and thus stay alive.

REM-sleep is accompanied with activity from the pontine brainstem which causes other parts of the brain to become extremely active, as active as during waking life or even more: these include visual, action and emotional reaction. However this activation of the brain parts that deal with the visual, action and emotional has been shown to be the result of random pontine activity.

Aside from that, several of the parts in the brain responsible for different type of memories are active in different stages of the sleep: the hippocampus for personal situation and event memories, another for task learning. The only one that does not seem to be active is the short term memory that would help to remember the dream itself.

Other brain parts get to be "deactivated" during dream stages. For example whatever you feel you're motorically doing in a dream, the actions you take hae no output. So, you can dream that you are running, but your legs won't be moving in reality. There are exceptions of course, like sleepwalking or sleeptalking (the more tired I am the more I will sleeptalk). Meanwhile the sensory input signals are shut out as well. What you see and hear happens solely in your mind. Someone touching you or splashing water on you for example has the most chance (42%) of getting through and weave its way into the dream, wheares flashing lights only have 23% chance in getting through. Sound only has a 9% chance.  

HOBSON'S ACTIVATION-SYNTHESIS THEORY (1994)

The frontal brain seems to react to the high level of random inner brain impulses by combining it into something that is at least semi-coherent. These findings led Hobson and McCarley to theorize in the Activation-synthesis theory that our frontal lobe invents or imposes a story out of the random noise (emotions, visual and auditory hallucinations) of the brain actvity during REM-sleep, because even in our sleep our mind is hell-bent on finding meaning in the random firing of neurons (see also how does tarot work - serendipity). Because the impulses are so random the brain cannot totally turn it into something coherent, hence we end up remembering bizar dreams where we hop from event and scene into the other.

However, they exaggerated the bizarreness of dreams. While dreams can be bizarre, at least some of those we do recall, many reported dreams in sleep studies where subjects were woken up are not as bizarre. Secondly, studies done by Solms showed that only with brain damage to the frontal lobe did dreams cease even if the pontine was still intact, yet 25 out of 26 subjects with lesions on the pontine brainstem seemed to be dreaming still.

REPAIRING THE BODY


If people deprive themselves of dream or REM sleep, the first thing the body will do is increase the dream sleep, recovering the loss of REM sleep almost precisely to a T. So, dreaming must be important. Long term sleep deprivation will lead to observed waking dreams, interference with memory and learning, difficulties to focus, haing a hard time to maintain a straight line of thought. Dreaming at the least seems important for our general daily well being.

When I studied for my Master in Industrial Design, I often needed to hand in or present innovative projects before a jury, often requiring at least 24 hours to stay up before the deadline. One time, I had to do several alterations to my design a week before the deadline, and I still had to make my mock-up, visual presentations and written report. Eventually I stayed up for 74 hours. I had been up for 3 days and 2 nights when I handed it in, and it took several hours before I finally got home again and could just lie on the couch.

The last 10 hours before going to university to deliver my project, it became harder and harder to do anything efficiently. Luckily I only needed to do a little bit of this and a little bit of that, but it took a lot of time to accomplish even the simplest of tasks. And by the morning, I found myself having waking dreams while I totally forgot what I was doing. When I wanted to call a cab to get me to university, I had to give up trying to find the phone number or even dial it. Instead I had to somebody else to make the phone call for me. And once I got home and laid on the couch, I was having whole sleep convesations for hours. Luckily for me I had not ot perform in front of a jury for that particular project. 

One could argue it was not the smartest thing to stay up for so long, but I had been awake already for more than 48 hours and feared that if I went to bed, I would never get up in time again to finish the job. My mother was so freaked out by my incoherent, stumbling behaviour those last hours that she made me promise to never ever do that again. What was even more amazing was that just one night of eight hours sleep was enough to recover from it all.

MEMORY REHEARSALS AND LEARNING


As the evidence made clear that the Activation-Synthesis theory fails to explain dream elements contradictory to what the theory predicted, Hobson came out with a new finding. Based on the brain wave activity in the hippocampus, of which one of the functions has been proven to be helping to store and revive recent memories related to our personal lives in the cortex (long term memory).

Neurons tend fo follow a path, much like a farmer plows the earth. It takes time and several plowings in order to make the path into a pattern. New experiences though may provoke neurons to become associated with other neurons not included in the previous brain pattern. But these new connections can easily fade away. Similary, if the farmer wants to plow new paths on his land, he will experience that his plow tends to slide back into the old track. So, these new connections need to be run down several times before assuring they will not fade away.

A dream sleep study with rats showed that the same neural path was activated during their dream sleep after they had learned a new maze to run. And researchers at the Weizman Institute, Israel, found that constant interrupting of dream sleep completely blocked learning, while interrupting non dream sleep had no such result. Subjects who learned a new task in the evening and had a good night's sleep were significantly faster and more accurate at the task afterwards.

Even one dream can show the dreamer having to solve a theme, repetitively, but each time from a different angle, or a bit differently. It's as if the brain is rehearsing and trying to find neuron paths that work and then strengthening the best neuron way.


RECALLING DREAMS

It is strange that if we dream at least four times a night, we recall so little of them. As already explained Hobson found out that the short memory storage center gets to have a rest, unless we are woken up. So, waking up during REM sleep enhances the chance to recall a dream. The most extensive dreams occur in the morning because our sleep is lighter and we wake up more easily. So, while not yet clearly established it is possible that the more hours we sleep the higher the chance we have to recall a dream. The ability to remember a dream spontaneously seems to be enhanced by factors such as how much we want to recall a dream and how important we think dreams are in general. If you are more interested in recalling a particular dream on a particular night you are more likely to do so. And the more visually creative you are, the more likely you will recall dreams.

Studies that showed this were done by Schechter, Schmeidler and Staal (1965) and review cited by Lynn Hoss. They compared recall ability between art, science and engineer students. Art students recalled significantly more dreams, and engineer sutdents the least. This is attributed to art students using the right-brain hemishpere more, whereas engineers use the linear leftbrain hemisphere the most.

Aside from creativity and ability to memorize visually, openness to experience and tolerance to ambiguity seem to help people recall their dreams more spontaneously.

So, if you find you don't recall any of your dreams try to sleep enough hours each night so the chances increase you wake up in one of the last REM sleep phases, train your visual memory, take an art class or do something visually creative or go to a musem and appreciate visual art, and gain an attitude to be open to the unpredictable experiences, and learn that problems may have several solutions with their benefits and downsides.

WHAT DO WE DREAM

We dream in color, but because of recall difficulties tend to forget the colours. Type 3 dreams are dominated by the visual experience (close to 100%) and sound (40 to 60%). Movement and touch is less frequent (15-30%) and smell and taste is almost totally absent (less than 1%). Emotions intensify with the progress of the dream.

sources:
science of dreaming (excerpts from Robert Hoss' "Dream language: self understanding through imagery and colour")
chapter 1: what is dreaming, by Alan Hobson, "Dreaming, a very short introduction"