The Prize:
Half of the 1981 Nobel Prize in Physiology or Medicine was awarded to Roger W. Sperry “for his discoveries concerning the functional specialization of the cerebral hemispheres.”
The Science:
Are you a lefty or a righty? Brain that is. Today, being left- or right-brained is so engrained in popular culture that it has made its way onto dating website questionnaires. In the 1960s, however, the discovery by Roger Sperry that the right and left hemispheres of the brain think and process information in vastly different ways was a revolutionary notion.
For decades before Sperry began his work on cognition and behaviour, it was known that the left and right “halves” or hemispheres of the brain perform different tasks. The two hemispheres are structurally identical mirror images of one another connected via millions of nerve fibres (known as the corpus collossum). Yet in spite of their apparent physical similarities, the two hemispheres behave differently.
By the 1960s, doctors and scientists topographically mapped many neural functions to specific regions of the brain. This mapping was aided by patients who suffered acute brain damage that affected only one or a few aspects of brain function. As early as the 1860s, Pierre Paul Broca mapped speech to the front part of the left hemisphere. In the 1940s, Canadians Wilder Penfield and Herbert Jasper were able to map motor function of one side of the body to the opposite brain half (i.e. the command to lift your right hand comes from your left brain).
Accumulating evidence led scientists to believe that the right brain was inferior to the left brain, which according to the tests of the day, was “in charge” of “higher” brain functions. The left brain was characterized as the dominant half because it was easy to study and appeared to be the seat of language, and therefore more highly evolved than its right counterpart. The apparent passivity of the right brain made it virtually intractable to experimental study.
However, when Sperry began his work in animal and human cognition he found something that today does not seem surprising: the full brain is greater than the sum of its parts. In the 1950s, Sperry severed connections between the left and right brains of chimps and found that each hemisphere could still learn and function, although the two halves could neither communicate with each other nor access information stored in the opposite half.
Intrigued by this, Sperry continued experimentation in humans. He had a perfect experimental model. Since the 1940s, certain severe epileptics were treated by surgically severing left and right brain connections (a commissurotomy). Severing this connection reduced seizure severity and frequency with otherwise little effect on behaviour and the patients’ ability to learn. Testing 10 commissurotomy patients, Sperry found ground-breaking evidence that the two halves of the brain are highly specialized. He found that the two halves of the brain were completely independent, each capable of thought, emotion, and memory inaccessible to the other half of the brain.
In split-brain experiments, a patient is told to look at the centre of a screen or piece of paper, and images or words are presented to one hemisphere at a time. When the image is placed to the right of the centre, only the right eye can see the image, and therefore only the left brain can process the image. Since commissurotomy patients lack connections between the two halves of the brain, each half can be tested independently.
When a word is presented to the left hemisphere, the patient can read it without hesitation. The same word presented to the right hemisphere conjures the meaning or context of the word, but the patient is unable to read the word. Thus, though the left brain can read the word “walk” at a crosswalk, it is the right brain that understands the context and meaning of “walk” so that you can safely cross the street.
Similarly, presenting an image of an object to the left hemisphere results in patients identifying the object’s name. The right hemisphere, however, can see the object, but is unable to communicate what the object is (the patient may even say he saw nothing), but can select the presented object from a group of objects placed before him. Despite being able pick up the corresponding object, the patient will have no idea why he selected the correct object from the group.
Interestingly, the isolated left brain can calculate and perform math functions easily, but the right-brain can only perform simple addition problems (up to the number 20), and is unable to subtract, divide, or multiply.
Like the old idiom, still waters run deep. Sperry’s results showed that the “passive” right hemisphere is actually “superior” to the “dominant” left hemisphere in certain respects. Although the left brain is responsible for speech, writing, and calculation, the right brain is involved in the complex tasks of spatial perception, word comprehension, and non-verbal communication. Right-brain tasks make up important mechanisms with which humans perceive and interact with the world. Some processes like music appreciation, intuition, and reading faces require right-brain functionality. The right brain only appears passive and inferior to the left-brain because it is essentially mute. It can think, process, and feel, but cannot communicate those thoughts because it does not contain the major language centre of the brain.
The Significance:
The work of Sperry, his students, and colleagues proved to be an inspiration to many new scientists. His work was instrumental in moving cognitive science forward. Brain lateralization experiments pioneered by Sperry and his group are still an active field of research.
Ivan Pavlov said that humanity can be divided into the thinkers and the artists. Pseudo-science and pop-psychology has jumped on the left-right duality to explain this phenomenon. A popular and effective book on learning to draw entitled, Drawing on the Right Side of the Brain (intended to teach the supposed artistically inept left-brainers to develop right-brain creativity), capitalizes on society’s over-simplification of brain function lateralization.
However, most evidence to date indicates that we require both halves of our brains for most tasks and there is never a time when one side of the brain is actively working while the other is merely idling. No one uses only one side of their brain. Although an attractive theory, the dominance of either side of the brain and its influence on personality is largely scientifically unfounded.
Sperry summed up his research and contributions best with his Nobel Prize acceptance speech words, “the great pleasure and feeling in my right brain is more than my left brain can find the words to tell you.”
