The Divided Brain

Hemispheres left controls right side of body and vice versa. Now the cerebral cortex is divided into two hemispheres- the left and right hemispheres.  For the most part the hemispheres exhibit what we call Contralateral control: which means the left hemisphere controls the right side of out body and the right hemisphere controls the left side.  However, there is no activity to which only one hemisphere makes a contribution.

Split-Brain Patients Corpus Collosum attaches the two hemispheres of cerebral cortex. When removed you have a split-brain patient. Between the two hemispheres is a band of nerve fibers called the corpus callosum.  The job of the corpus callosum is to help the two hemispheres communicate with each other.  In some cases of people with severe epilepsy, the corpus callosum is surgically removed and the seizure activity decreases.  However, these people lose the ability of there hemispheres to communicate to each other- they are called split brain patients.  They actually have two separate brains inside their head, and one brain has no idea what the other is doing. Studies of people with split brains provide us with an understanding of the two hemispheres’ functions.

Each of our retinas is divided into a left visual field and a right visual field. The pencil in the left visual field is sent to the right half of each retina. The apple in the right visual field goes to the left half of each retina.

The information received in the right side of each retina travels to the right hemisphere. The information received in the left side of each retina travels to the left hemisphere. Since the corpus callosum is severed, the two hemispheres cannot communicate with each other.

In one experiment, psychologists asked split brain patients to stare at a dot.

While staing at the dot, the psychologist flashed the word HEART on the screen.

The HE appeared in their left visual field (which transmits to the right hemisphere) and ART in the right field (which transmits to the left hemisphere).

When he then asked what they had seen, the patients said they had seen ART.

https://www.youtube.com/watch?v=ZMLzP1VCANo But when asked to point to the word with their left hand (controlled by the right hemisphere), they were startled when they pointed to HE. Given an opportunity to express itself, each hemisphere reported what it had seen. The right hemisphere (controlling the left hand) intuitively knew what it could not vervally report. When a picture of a spoon was flashed to their right hemisphere, the patients could not say what they had viewed. But when asked to identify what they had viewed by feeling an assortment of hidden objects with their left hand, they were able to select the spoon. The patient would then be surprised that they got it right.

Split Brain Behavioral Experiments (‘Joe’)- 4:36 https://www.youtube.com/watch?v=ZMLzP1VCANo

Brain Plasticity The ability for our brains to form new connections after the neurons are damaged. The younger you are, the more plastic your brain is. http://www.youtube.com/watch?v=2MKNsI5CWoU