Anatomy of Brain: –
It is hard for most of us to imagine what it would be like to have one of our most taken-for-granted faculties suddenly no longer available to us, like the ability to respond emotionally to our visual experience. Indeed, what is most intriguing about these stories is the way in which they challenge one of our most fundamental intuitions—our sense that the self is a single, unified whole. Repeated throughout the neurology literature are cases in which damage to a specific part of the brain leads to the loss of some specific aspect of our ability to perceive and respond to the world. Damage one part of my brain and I’ll lose the ability to learn any new facts. Damage another part and I’ll be unable to recognize faces. Damage another area and my experience of the world will remain intact, but I’ll be unable to find the words I need to speak clearly about it. Damage still another part and I’ll lose the ability to pay attention to half of my visual field, but I will be convinced that the half I’m seeing is the whole picture. As a result, in the morning, I’ll only shave half of my face. Taken together, the data from neurology suggest that despite our brain’s ability to organize our experience into a seamless unity, we are, in fact, made up of many parts, the loss of any of which can have dramatic effects on the whole.
However ignorant we may be of brain science, most of us are familiar by now with the idea that our brain has two hemispheres, a left one and a right one, each responsible for very different aspects of our behavior. Our dominant left brain, we are told, is more analytical; our right brain more emotional, creative, and intuitive. Although much of the popular psychology literature on the right brain–left brain distinction has been, in the eyes of neuroscience, exceedingly simplistic and inaccurate, the basic fact—known in the field as “hemispheric specialization”—is well established. In a normal brain, these two hemispheres communicate with one another through a large band of nervous tissue known as the corpus callosum (larger in women than in men, incidentally, accounting for their superior ability to multitask, among other things). But what would happen if the connection between these two halves of the brain was severed, leaving us, in effect, with two brains in our head? Would we end up with two different selves? Over the past few decades, a group of neuroscientists have had the chance to find out.
Epilepsy comes in many forms, some mild and some severe. In its worst manifestations, it brings with it nearly constant seizures that make life almost impossible for the patient. In an attempt to control these severe cases, in the 1960s neurosurgeons began cutting the corpus callosum to prevent the seizures from spreading from one side of the brain to the other. The procedure was re- markably successful, and to the relief of the doctors who pioneered the treatment, patients generally recovered well and were able to live relatively normal lives. But in these “split-brain” patients, psychobiologist Roger Sperry soon recognized a rare opportunity to study the differences between the two hemispheres in a way that had never been possible before. Over the decades that followed, he pioneered a series of studies that ultimately earned him a Nobel Prize. Most of these split-brain studies focused on illuminating the functional differences between the two hemispheres, but along the way, Sperry and his colleagues began to realize that there were implications to what they were seeing that went far beyond the scope of their initial questions.
One of the most commonly known facts about hemispheric specialization is that the right brain controls the left side of the body and the leftbrain controls the right side. Where visual input is concerned, the same rule applies. The left half of the visual field (of each eye) is routed to the right brain and vice versa. Knowing this, researchers realized that by presenting information quickly to only one side of the subject’s visual field, they could ensure that the information only reached one side of the subject’s brain. This technique provided the cornerstone of their research.
Employing this method, researchers had learned early on that the dominant left brain, with its ability to reason and use language, is the home of what we usually think of as the conscious mind. For instance, when asked to report on information that had been presented to their left-brain alone, subjects could speak about it quite normally. When information had been presented only tothe right brain, by contrast, subjects seemed unaware of it. As the research progressed, however, the picture grew more complex. For instance, when the right brain was shown an image of a spoon, the subject’s left hand (which is controlled by the right brain) could successfully identify an actual spoon from among an assortment of objects, even though the subject claimed to have no conscious knowledge of having seen it. Despite its inability to express itself, the right brain nonetheless seemed to have a will and mind of its own. Eager to test this, Scottish neuroscientist Donald MacKay devised a twenty-ques- tions-type guessing game and successfully taught each of the two halves of a patient’s brain to play it—first against him and then against the other half. But this image of the two halves of one brain competing with one another soon moved from the experimental to the macabre, as split-brain patients began to develop the bizarre malady known as “alien-hand syndrome.”
The idea that splitting the brain amounts to nothing less than splitting the self is a challenging one with enormous implications for our understanding of the brain’s role in creating consciousness and even individuality. Therefore, it is no surprise that it has remained a controversial finding, even among scientists. But for the man who was awarded the Nobel Prize for his pioneering work in this area, the experience of working with split-brain patients for many years all pointed in one direction. “Everything we have seen indicates that the surgery has left these people with two separate minds,” Sperry wrote. “That is, two separate spheres of consciousness.”
Cerebral Cortex (cerebrum): –
This is the most highly evolved part of our brain. The furrowed, quarter inch thick slab of gray matter that covers the surface of the brain is divided in two hemispheres and four lobes. Creativity generally resides in the right hemisphere, analytic ability in the left. Frontal Lobe – Area of brain just behind eyes, which controls intellectual functioning, including thought process, meaning and behavior. Temporal Lobe – Located on lower sides of the brain, the temporal lobes are responsible for smell, taste, hearing and visual associations. Parietal Lobe – Upper portion of the brain, just under top of skull. The parietal lobes are responsible for higher sensory and language functions. Occipital Lobe – located in the rear area of brain, the occipital lobes receive the visual information from the eyes.