Language in the Brain

I want to start this post by first stating the oft-repeated paradigm that you're either "left-brained" or "right-brained" has almost no scientific basis.  Your brain is basically a mess of biological wires in the form of axons.  Information crosses from one hemisphere of the brain to the other along the corpus callosum as well as other minor pathways.  Without both parts of your brain, you cannot function normally.  (Just look at patients with hemi-neglect.)  That being said, there are certain functions which are lateralized to one side of your brain.  Language -both comprehension and production- is a key example.

There's a particular experiment called the Wada Test which demonstrates this lateralization particularly well.  The participant is injected with a temporary gaba agonist through the left carotid artery.  Gaba is an excitatory signal so by blocking it, you essentially put the left hemisphere of the participant's brain to sleep.  The participant remains conscious, though they lose the ability to use the left side of their brain.

The interesting bit is that they lost the ability to compose speech.  You can ask them questions but they will be unable to reply in a coherent way.  But if you give them a matching task that requires both comprehension and identification, they are able to preform it easily.  Their main impediment is their verbal abilities.

Wada testing

But the really curious part is that this doesn't work on everyone.  Because although nearly all people have their language centers lateralized to the left side of their brain.  About 95% of right-handed people and 70% of left-handed people have their language centers based in the left hemisphere of the brain.  But in those remaining 5% and 30%, they seem to have a less focused center for language.

Not much research has been done on this topic.  It's unknown why left-handed people are more prone to the un-lateralized form.  But one possible indication is an inability to remember/distinguish between right and left.  So if you have a chronic problem of separating right from left and are left handed, there's a good chance your language center isn't in the usual location of the brain.