Does Callosal Syndrome Provide Evidence for Duality of Consciousness?

 by Henry Hayter

 

A corpus callosotomy procedure is a surgery performed on people who are suffering from severe and repeating seizures typically myoclonic(sudden jerk), atonic (muscle relaxation) and tonic seizures (muscle contraction). The procedure itself sees the severance of the main fibre bundle connecting the right and left sides of the brain to one another ( the corpus callosum ). The corpus callosotomy has an 80% success rate in reducing the frequency of seizures in those who have undergone it, this sort of a success rate is obviously a very positive side to the treatment yet it carries some major side-effects the main of these being the loss of ability for the two hemispheres of the brain to intercommunicate.

The loss of communication between the two sides of the brain results in what can appear initially as two separate consciousnesses that being that often the two halves of the brain will act independently performing the tasks that they are able to. A popular example of this side effect is (shown below) when an individual has had a corpus callosotomy will be shown a word through their left eye - which is controlled by the right hemisphere of the brain and lacks the ability to process ideas into speech. The left hand will be able to identify the item that the word represented yet when asked what was seen the individual will reply more often than not `nothing` as the left hemisphere - the right eye did not see anything. This raises the question of a duality of consciousness; the two hemispheres are incapable of coordinating responses to questions. The hemispheres while not able to directly communicate via nerve impulses can still somewhat function as a cohesive unit. For instance if the object was placed in the view of the right eye the left hemisphere would be able to verbally communicate what the object was which upon hearing the right hemisphere would be able to pick the object from a group similarly to the experiment mentioned earlier.  This seems startlingly similar to a dual consciousness given that the two hemispheres can coordinate themselves in such a way - somewhat similarly to teamwork exercises.

The idea of dual consciousness can manifold itself physically as well through Alien Hand Syndrome which is a neurological disorder which will see one hand interrupting the task of the other without the individual realising. This has been recorded where a patient who had undergone the  corpus callosotomy found themselves unknowingly unbuttoning their shirt with their left hand as they were buttoning it up with their right . There is no cure currently for the alien hand syndrome nor is there a permanent fix for the `dual consciousness` that is caused by the procedure.

The debate about whether or not the callosotomy causes the development of a second consciousness is still not resolved partly due to the fact that consciousness lacks a universally accepted definition but primarily due to the fact that other causes of the phenomena mentioned exist. Such as the interruption of processes completed on both hemispheres of the brain within the Supplementary Motor Area causing the development of alien hand syndrome in people who have received a corpus callosotomy. The region of the brain is shown below and can clearly be seen to be in both hemispheres thus explaining the interruption caused by the severance of the corpus callosum.

 Finally the symptoms of split brain or Callosal syndrome can also be seen in people who have suffered a stroke or seizure - although the symptoms are often less permanent. This demonstrates that the removal of the corpus callosum is not the only cause of the mentioned phenomena.

Overall it is hard to say that the corpus callosotomy causes a dual conscious to develop although it does illustrate the fascinatingly complex processes of the brain given the adversities that the two hemispheres are able to overcome despite a lack of direct communication and through the development of several bizarre and quite alien seeming symptoms - such as the aptly named alien hand syndrome.