Wednesday, 19 February 2014

Neuromyths 102- the left/right brain myth!

First, thanks to everyone who read and shared and commented on my first blog post, it's greatly appreciated!

In this next post I'd like to take on another very common neuromyth...

You are either a left-brained thinker or a right-brained thinker

I'm in no doubt that you have heard of this at some point in your life, and at face value it seems to be logical- there are people who are right or left handed, or footed, most people have an eye that is stronger than the other etc etc... but how did people come up with the idea that you can have a dominant brain hemisphere? how can there be brained-ness (probably not a real word)?

Well, many people who push this kind of thinking about the brain normally use this kind of logic: if the left hemisphere is more involved in emotion and communication etc then people who are more in touch with their own and other people's emotions must be left brain dominant; and as the right brain is more involved in logic and reasoning, then people who are more rational and logical must be right brain dominant. Makes sense right? 

Well it would, if it weren't for the fact that there is absolutely zero evidence to support this.With the development of brain imaging (you've probably heard of MRI) this sort of "old wives tale neuroscience" has been very hard to continue to support. 

The most recent and most comprehensive blow to this myth was a study in 2013 Neilson et al (and others) which you can read for yourself here. What this study found was that there is lateralisation of certain functions within the brain (eg Brocca and Wernicke areas on the left hemispheres were more involved in language) but that there was no evidence to suggest that people showed a preference to use a certain hemisphere over others. If you still aren't convinced, or need more explanation, here is the wikipedia page on lateralisation of brain function. 

Now then, what is interesting is that these lateralisations can differ greatly. For instance, right handed people show about 90% lateralisation of language to the left hemisphere but in left handed people at can be almost an even split between people who process language in their left and right hemispheres. You should have noticed by now that I keep saying tend to and more involved a lot, and that's because these things are not absolute. If we stick with the example of language, accents and intonation (how someone said something) are actually processed in the right hemisphere! You also see that when a brain region is lost (eg due to trauma or stroke), the neighbouring regions and/or the corresponding region on the opposite hemisphere can take on the roles of the lost region! This phenomenon is called neural plasticity, and requires a whole series of blog posts all by itself. 

So as you can see, the more you try to generalise and simplify the brain, the more  wrong you become! Instead of thinking of the brain as having distinct domains that do not talk to eachother, think of it as an interconnected mess of circuits that are always communicating with and competing against one another, and also constantly changing with experience. 

I hope you enjoyed this post, again feel free to comment on this blog if you have any questions or suggestions, share it around on twitter, facebook etc if you like (it's always appreciated!) 


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