Friday, 22 June 2007

Why dream?

We all know what dreaming is, experiencing sensations such as images and sounds during sleep that we usually cannot control. Lucid dreaming is when the dreamer is aware they are dreaming and can sometimes alter their actions and the dream world. Anxiety is the most common felt emotion during dreams. Dreaming is associated with the REM (Rapid Eye Movement) stage of sleep. We go through ~4 cycles of REM sleep. All the muscles in our body are paralysed apart from the muscles in your eyes hence the name.

But why do we dream at all, nearly all mammals and birds appear to do it. Suggesting it must be evolutionary beneficial but how? Some people have thought dreams were messages from god or predictions of the future. Early psychologists like Freud were interested in dreams and their meanings. He believed dreams were wish fulfilment. Your unconscious mind doing things your conscious mind does not allow it when you are awake, but your ‘superego’ sensors your dreams. Part of this is symbolism, items and events represent what you really want. Freud has said not everything is a symbol, ‘sometimes a cigar is just a cigar’. He thought if you understand what they meant and resolve the deep arguments within yourself then all is well. I have never thought this made evolutionary sense…how many psychoanalysists were there in cavemen times to help them by charging +£60 to listen to them speak? Not many I would assume but I have no data on the matter.

Neuroscientists have also tried to explain why we dream. The great neurobiologist Crick (yes I do mean the on and only Crick) put forward the theory of reverse learning as a reason for why we dream. This theory says we dream to forget! The theory says we take in too much info in during the day so at night we erase these memories. Otherwise they would become damaging to you. This theory has little experimental support. It doesn’t explain why newborns sleep and spend so much time in REM (assuming they are dreaming). Also why do dreams have a story if they are simple a deleting mechanism? Why not simple flashes of sound and images, or has our brain come to make sense out of this, what function could that have. Lloyd et al. (unpublished) criticises it by showing more dreams are experienced when revising and yet much of the information stays. He suggests dreams are either a way of rehearsing or organising the information. But he fails to explain why dreams usually have little to do with what has been learnt. But it is clear information is not being forgotten.

Dreams have also been seen as a way of solving problems. Are you in fact thinking during dreams and coming up with ideas? This seems hard to grasp – you are actually thinking but have no control. KekulĂ© figured out the structure of benzene through dreaming of snakes biting its tail making a ring. Lloyd et al. also provides evidence of this. The subject woke up from a dream with the answer to chemistry homework that they were unable to solve beforehand. However there is no evidence people who do not pay attention to dreams have more difficulties in life than those who do.

It is hard to figure out what is going on with dreams, we cant figure out what memories are on the molecular level let alone how dreams arise and what function they have.

Just remember you do not know you are dreaming in non-lucid dreams then how can you prove you are not dreaming right now! (warning the devil is in me)


Menelaos Symeonides said...

Excellent, I was just yesterday wondering why we sleep at all, after being reminded that snakes and dolphins don't sleep. I suppose this answers the question in part (we sleep in order to dream?) but you don't really have to be asleep to dream.

Anyway, as for Crick's theory, I think it's not as unsupported as you think. There's decent evidence that neuronal death is how memories form, so basically there is competition between neurons and the ones that aren't being used will grow weaker (less connected) and eventually be killed off to allow the more useful ones to expand their dendrites. I'm not sure if there is more neuronal death going on during sleep, but we could look that up.

James Lloyd said...

good point, i didn't know that.
the reasons why we sleep could be very different to why we dream, i think. or originally. their are a couple of theories of sleep. possibly it started to save energy when you cannot hunt. if you are a night hunter and you are exposed during the day you can sleep during the day (and vice versa). i don't like this theory a lot. a better one is it allows neurotransmitters to be regenerated. but during REM sleep they are then being used! so the two are perhaps opposing forces. i don't think that is a much of a better one. do you have any better ideas? I aren't up on this area. just interested.