Split Brain

Definition: A split brain patient is someone who has undergone a surgical procedure that severs the corpus callosum, the thick band of neural fibers connecting the two hemispheres of the brain.
Reason for Surgery: This surgery is typically a last resort for individuals with severe epileptic seizures that do not respond to medication.

The human brain consists of two hemispheres: the right and the left.
Each hemisphere controls the opposite side of the body (Contralateral Control).
- Right Hemisphere: Controls the left side of the body.
- Left Hemisphere: Controls the right side of the body.
Visual Processing:
- Objects in the right visual field are processed by the left hemisphere.
- Objects in the left visual field are processed by the right hemisphere.

Language Functionality: Language comprehension and expression are localized exclusively in the left hemisphere of the brain.
Key Point: A split brain patient will often experience challenges in verbalizing information processed in the right hemisphere due to the severed corpus callosum.

The primary goal of the surgery is to reduce the frequency and intensity of epileptic seizures.
In many cases, patients experience a significant reduction in seizures post-surgery; some may be completely free of seizures.

A common and bizarre side effect observed after the corpus callosum is severed is conflicting behaviors between the two hands of a split brain patient.
Example of Antagonistic Behavior:
- One hand may attempt to dress the patient while the other hand interferes, indicating a lack of coordination between the hemispheres.
- For instance, a patient might reach for a shirt with one hand while the other hand throws it away.
This side effect typically subsides over time, usually within a few months.

Key researchers: Roger Sperry and Michael Gazzaniga conducted significant research on split brain patients.
Experimental Setup: Patients were shown dots followed by words either in the left or right visual fields.
- When a word is flashed to the left, it goes to the right hemisphere, which cannot verbalize it due to the lack of language centers.
- If asked to draw the word seen, patients can do so with their left hand but cannot verbally say the word.

Visual Field Testing:
- Left Visual Field: A word (e.g., "cat") shown here is processed in the right hemisphere.
  - Patient is unable to verbally express the word but can draw or select it using their left hand.
- Right Visual Field: When a word is shown here, it is processed in the left hemisphere.
  - Patient can verbalize the word easily, as language functions reside in the left hemisphere.
Example Experiment:
- Heart and the word "Heart": If the letters are split with "art" in the right visual field and "he" in the left visual field, the patient may say "art" (from the left hemisphere) but point to "he" (from the right hemisphere) with the left hand.
- Selecting Objects Experiment: If a spoon is presented in the left visual field:
  - Patients claim they saw nothing but can choose the spoon with their left hand when prompted, evidencing that the information is present in the right hemisphere.

Post-surgery consequences provide profound insights into the functionality of the human brain, particularly the specialization of regions for specific tasks (like language) and how disconnection can lead to conflicting responses between hemispheres.
Further watching of video clips demonstrating the behavior of split brain patients will enhance understanding of these concepts.