Human Responses to the Human Split Brain :: Biology Essays Research Papers

When neuroscientists first made direct contact with the right cerebral hemisphere of the mavin, during neurologic tests of split brain human subjects, it was as if they had found intelligent, albeit speechless, life on Mars. At a time when brain imaging techniques were crude or nonexistent, the only way to pick up and communicate with the brains right hemisphere unimpeded by the left hemisphere was by testing split brain subjects (1). The right hemisphere, previously supposed mute, illiterate, mentally retarded, and completely subordinate to the left hemisphere, had a mind of its own (1). While it could not speak, it could respond to commands and questions via its contralateral control of the left hand. It had different abilities and even opinions and steamy states than the neighboring left hemisphere (2). These discoveries led to a model of hemispheric specialization of normal human brain function, with an analytic, verbal, problem solving left hemisphere and a visuospatial, syn thetic, creative right hemisphere (1, 2). The formation of this model in turn offers insight into the brains of the observers as well as the observed. The observers behavior supported both(prenominal) of their own hypotheses about the human brain, split or unsplit.The term split-brain is commonly used to describe a person whose star callosum has been surgically severed (3). The corpus callosum, comprised of approximately 200 million neuronal fibers connecting the left and right hemispheres of brain, exists only in mammals brains, and is largest in human brains (1, 3). Until the 1960s neuroscientists were unsure what purpose the corpus callosum served (3). By sight deficits in split brains functions, scientists could better assess the corpus callosums function (1). Roger Sperry and his colleagues pioneered the operation severing the corpus callosum, known as callosal commisurectomy, in the 1960s, as a prevail ditch effort to control the seizures of life threateningly severe epile psy by creating a fire wall to prevent electrical impulses from traveling between hemispheres (1). This manipulation was successful, and after recovering from the surgery, the split-brain patients appeared normal in every day interactions and even during a routine physical exam (1). However, Sperry and his colleagues, after extensive and specific neurological tests of split brain patients, posited that the corpus callosum communicated stimuli and responses between the two hemispheres, each specialized for different cognitive functions (1).Using a tachistoscope, Sperry delivered visual stimuli to a single visual field of the subject (1). He discovered that, with the exception of olfactory stimuli, the hemispheres of the brain receive sensory stimuli and exercise motor control contralaterally (1, 3, 5).