In the latest of our shortlisted entries to the 2011 Wellcome Trust Science Writing Prize, Jerome Langford tells us how the brain is more than the sum of its parts.
Very few people can claim to have never paused for a little introspection on who they really are. From psychology to philosophy, the fascination with identity has been tirelessly studied over many years. Aside from academic interest, the preservation of cultural and spiritual identity in this modern age of homogenising globalisation is an issue close to the hearts of many.
For most people however, life is too short to worry about whether or not you truly are who you think you are. Between juggling work and maintaining an active social life, there is little room for some good old-fashioned existential musing. To counter this prevailing attitude, let’s take a glimpse into the bizarre and astonishing world of ‘split-brains’.
Rather than being a single mass, our brains are split down the middle into two hemispheres. These work in tandem with one another by communicating through the corpus callosum, a clump of nerves that transmit information from one side of the brain to the other. We take it for granted that our brain represents ‘us’ as a cohesive whole, as we do not find either half conflicting with the other. Each side of the brain controls the opposite side of the body’s muscles, and the corpus callosum allows both sides of our brain to seamlessly co-operate, allowing us to walk and co-ordinate our hands together.
There are cases however, where this link between the hemispheres must be severed – most commonly in cases of severe epilepsy. After the operation, the patient is referred to as having a ‘split-brain’, the effects of which are incredible.
If you were to talk to somebody after they had undergone a split-brain operation they would seem, to all intents and purposes, to be no different than they were previously – one mind and one body. But this is an illusion, for you are only able to talk to the hemisphere of the brain that controls speech. In their head now lies a silent witness – a second hemisphere, unable to speak, but one has developed a separate consciousness of its own, that thinks for itself and hears all that you say.
Psychologists have conducted tests that allow these mute observers to converse and answer questions. Some of them express different aspirations, personalities and even religious beliefs to their verbally endowed counterparts. It is amazing to see how the verbal hemisphere is completely unaware of the thoughts of the other but remains influenced in a way that remains unexplained.
One experiment involved showing patients two houses. In the verbal hemisphere’s field of vision, the houses were identical. Subjects expressed their confusion as to the point of the test when asked to select which house they preferred. In every case, they selected the second house shown. What they didn’t know was that the first house, in the vision of the of the other hemisphere, was shown to be on fire. In some unconscious way, the other half of their brain had silently influenced their decision without their knowledge. When questioned on their choice, most could not give any reason why they chose the second house.
These cases, although slightly unnerving, are generally harmless. In a small minority of cases however, the second hemisphere’s role of silent witness can take a nightmarish twist. The usually passive observer can rebel against their speaking partner and refuse to co-operate. The limbs controlled by the observer can ‘go rogue’ in what is often termed ‘Alien Hand Syndrome’, where the limbs controlled by the non-verbal hemisphere act against the other’s wishes – refusing to walk, preventing the other half from smoking, changing the television channel and, in one case, even attacking a loved one. We sympathise with the speaking side instinctively, but we can’t begin to imagine what it is to be their mute companion, trapped without a voice in the same head. Can we say that either of the halves are the same person who underwent the operation? Both? Or perhaps even neither?
Cases of split-brains are highly unusual, as medical techniques have made the complete severance of the corpus callosum extremely rare. Despite potentially significant ramifications for religious ideas of the soul and relevance to debates on cloning, it remains relatively obscure. One thing that we can console ourselves with however, is we can know that no matter how difficult the modern struggle for identity might seem, it pales into insignificance when compared with the split-brain patient.
Jerome Langford
This is an edited version of Jerome’s original essay. Views expressed are the author’s own.
Find out more about the Wellcome Trust Science Writing Prize in association with the Guardian and the Observer and read our ‘How I write about science‘ series of tips for aspiring science writers.
Over the coming months, we’re publishing the shortlisted essays in this year’s inaugural competition.
Image Credit: Wellcome Images
Filed under: Science Communication, Wellcome Trust Science Writing Prize Tagged: Brain, Epilepsy, Split-brain, Wellcome Trust Science Writing Prize
