How we got Split-Brain Studies

One more cringe worthy surgery to contemplate might be Split-Brain surgery. A process by which neurosurgeons cut the corpus callosum, that then stops nerve fibres carrying messages from one side of the brain to the other. In epileptic people, quickened activity between both sides of the brain causes epileptic fits, and therefore, separating them, reduces the rate of epileptic seizures. (Calson, 2010)

The first research in this field was done by Bykov in the early 1900’s, where he worked in animals in Pavlov’s laboratory. By 1924 he had discovered that sectioning the corpus callosum in dogs prevented the contralateral skin related conditioning of salivary reflexes. (Glickstein & Sperry, 1960)

Corpus Callosum

The Corpus Callosum. Source: Psych Web

The first human case was reported in 1940 by Van Wagenen and Heeren, when the callosum was split as an attempt to cure epilepsy. The procedure was successful both in controlling epilepsy, and in finding new research on the corpus callosum. (North Dakota State University)

Years later, scientist Roger Sperry, and colleagues, performed further research in to split brained patients. They found that, although in day to day life, their behaviour seemed practically normal, that the cut off communication meant that the two half brains were actually operating independently of one another. Their work on animals showed that each half of the brain could be taught contradictory activities, with no perceivable mental conflict (Sperry, 1975).

The same behaviour is exhibited in humans. Post split-brain surgery patients have reported that their left hand seems to have a mind of its own. They may find themselves interestedly reading a book, yet then spontaneously, and through no conscious choice of their own, put it down. (Calson, 2010)

The different experiments performed, assessing responses to stimuli, opened up a whole new dimension of research, examining the brain in a new, not previously obtainable situation. The studies revealed where both sides of the brain are specialised. Sperry was awarded the Nobel Prize in Physiology or Medicine in 1981 (Horowitz, 1981).

What impresses me here is how a potentially controversial operation endured through the ages, to be not only acceptable, but also incredibly useful both in controlling epilepsy and understanding mind. If the idea were suggested today, ethical alarm bells might ring, yet through a century long research process, we now have scientifically grounded theories on the callosum and the two sides of the brain.

Is this a game that we have to play in order for research to gain widespread favour? Is that the way it should be? How much control do we have over what science achieves for humanity? It’s as if science itself is alive and kicking, an intelligence in its own right, with whom we work, that we might progress.


Carlson, N. R., (2010), Introduction. In N. R. Carlson, Physiology of Behaviour (pp. 2-27). Boston, MA: Allyn & Bacon.