Notes on Split Brain Research – Joe's Case Study

Split Brain Joe: A case study of a man who underwent a procedure to sever his corpus callosum to alleviate severe epileptic seizures.

• The corpus callosum is a bundle of nerve fibers that connects the two brain hemispheres, allowing communication.

Epileptic Seizures: Joe experienced severe seizures due to misfiring electrical activity in his brain, prompting surgical intervention.

Two Hemispheres of the Brain:

• Normal Brain Function: In a typical brain, the left hemisphere controls the right side of the body and vice versa.
• After the surgery, the two hemispheres in Joe's brain can no longer communicate, resulting in separate operations.

Experiments with Joe:

• Initial Setup: Joe focuses on a cross in the center of a screen, with words flashed to either the left or right of the cross.
• Left Hemisphere: Words flashed to the right of the cross are processed by the left hemisphere, which is responsible for speech.
• Right Hemisphere: Words flashed to the left are processed by the right hemisphere, which Joe cannot verbalize but can visually recognize (e.g., seeing a telephone but unable to name it).

Classic Experiment by Mike Gazzaniga:

• Tested the specialization of the two hemispheres:
• Right hemisphere draws a toad when it sees a word, while the left hemisphere sees a stool and can speak about it.
• The left brain constructs narratives to explain actions dictated by the right brain, showcasing its interpretative capabilities.

Recognition of Shapes/Objects:

• When shown two words, one to each hemisphere, Joe illustrates what the right side saw (toad) but can only verbally express what the left side (stool) saw after he has seen both images.
• Joe's left hemisphere concocts plausible rationales, demonstrating a unique trait of human cognition: the desire to understand cause and effect.

Face Recognition:

• A new experiment involved artwork by Archimede—a painter known for creating faces from inanimate objects.
• Joe's right hemisphere recognizes faces, while the left hemisphere focuses on the individual components making up the face.
• This suggests a specialized role for the right hemisphere in processing faces.

Survival Skills:

• The brain's design may have evolved to quickly recognize faces for social interaction and survival, determining whether someone is a friend or foe.
• The left hemisphere, however, is crucial for complex reasoning and creative thought, underscoring its importance in human intellect and invention.
• Mike Gazzaniga highlights the vital role of the left hemisphere, summing up with "don't leave home without your left hemisphere."