Synaesthesia Part One: The Science Side.

brain-scans

Tasting colours, hearing shapes and seeing numbers’ personalities might seem to some as an experience available only to those on illegal hallucinogens. Well, you’d be surprised, but many people have these experiences on a daily basis.
What happens is, they have a brain condition called Synaesthesia.
Now, the word condition makes it sound like a disease, but really, it’s far from a disease.

Synaesthesia is the simultaneous perception of different senses. 
For example, seeing a colour when presented with a letter or seeing shapes when listening to music. Everybody perceives it in a different way, and there are many possible ways of having it, depending on what senses are mixing.

But why? Or how?
Two main theories have been formulated to try to explain the condition:

1. Hyperconnectivity due to defective pruning in early development.

Quite a mouthful, but it’s not a very difficult concept to understand if we understand neural pruning.
Often described as “Use it or Lose it” neural pruning is the process through which your brain gets rid of connections which you don’t use anymore. This is done so that the brain runs more efficiently. Neural pruning doesn’t happen because “you’ll run out of space” in the brain. That’s not very plausible, considering a human brain has approximately 86 billion neurones. Pruning helps ensure that energy is not wasted on connections which are not being used.
During early development, the human brain makes an insane amount of new synapses every second, many of which, become irrelevant by the time a child turns 2. This is why the brain gets rid of many of them, losing up to 50% of these synapses by the time a child turns ten.
It is hypothesised however, that people with synaesthesia have some connections in their brain that should have been lost during pruning. This causes some cross-activation in their brains. For instance, if one area of the brain is activated (let’s say a person receives an musical input) then another unrelated part of the brain is activated simultaneously (the visual cortex perceives a colour).
Researchers believe that in babies, these coincidences happen frequently, whereas in adults, they are a lot more rare.
This could lead us to believe that through pruning, most people lose that relation between the senses. Well, it seems like synesthetes do…

2. Disinhibited Feedback.

What this theory suggests, is that synesthetes’ brains are not very different from normal people’s.
Multiple pieces of information received by the brain will typically be sorted out so that they make sense. They remain in the central processing area and all the extra information is inhibited.
However, in a synesthete’s brain, this electrical feedback is not ignored and so it is free to travel down to other ares of the brain and activate them, causing a seemingly unrelated experience.
This theory is supported by the experiences of people who use hallucinogenic drugs and experience similar things to synesthetes.

Both of these theories have been supported by research and both seem like good explanations of this condition.

Next week, my sister will tell you all about how synaesthesia has influenced art in the second part of this exploration.

In the mean time, if you think you experience synaesthesia or want to learn more about it, I highly recommend VS Ramachandran’s paper: “Synaesthesia- A Window Into Perception, Thought and Language”, which I based a lot of this post on. Also make sure to check out the websites I consulted, as they offer a lot more detailed information.

A is definitely red, E and 3 are blatantly green and the number 5 is overwhelmingly yellow… Do you feel the same way?

-teresa-

Sources:
http://neurowiki2013.wikidot.com/individual:why-synesthesia-occurs
http://synaesthesia.com/en/Information/einfuhrung/
http://synaesthesia.com/en/information/state-of-science/synasthesie-generell/
http://courses.evanbradley.net/wiki/doku.php?id=the_disinhibited_feedback_theory

VS Ramachandran, “Synaesthesia- A Window Into Perception, Thought and Language” http://www.imprint.co.uk/rama/synaesthesia.pdf

Image credit: https://kitchen-theory.com/wp-content/uploads/2015/01/brain-scans.jpg

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