Overview
This lecture explores how splitting the brain's hemispheres affects consciousness and behavior, using the case of patient Joe who underwent corpus callosotomy for epilepsy.
Brain Hemispheres and the Corpus Callosum
- The left and right hemispheres normally communicate via the corpus callosum, a bundle of nerve fibers.
- Severing the corpus callosum (as in Joe's case) prevents information exchange between hemispheres.
- Each hemisphere can function independently without the person noticing any subjective difference.
Effects of Split-Brain Surgery
- Language and speech are mainly controlled by the left hemisphere.
- Visual information presented to the right of fixation goes to the left hemisphere; Joe can name these items.
- Visual information presented to the left of fixation goes to the right hemisphere; Joe cannot name these items.
- Joe can use his left hand (controlled by the right hemisphere) to draw images he saw but cannot name.
Insights into Consciousness
- The right hemisphere can process and respond to information nonverbally, even when the left hemisphere is unaware.
- Split-brain cases show that complex, unconscious processes occur outside of our conscious awareness.
- The mind consists of independent and semi-independent agents (processes) across the brain.
- The left hemisphere integrates these processes into a unified sense of self and understanding of the world.
Key Terms & Definitions
- Corpus Callosum — Bundle of nerve fibers connecting the left and right brain hemispheres.
- Split-Brain — Condition where the corpus callosum is severed, disconnecting the two hemispheres.
- Conscious Awareness — The part of the mind where we are actively aware of thoughts and perceptions.
- Non-conscious Processes — Brain activities that occur without conscious awareness.
Action Items / Next Steps
- Review examples of split-brain experiments and their outcomes.
- Read about Michael Gazzaniga’s research on brain lateralization.