In a series of studies, Roger Sperry and Michael Gazzaniga tested patients whose corpus callosum had been severed to relieve severe epilepsy. Researchers flashed an image of a spoon to the patient's left visual field while the patient stared at a central dot. When asked what they saw, patients verbally reported "nothing." However, when asked to use the left hand to select an object hidden behind a screen, patients correctly chose the spoon.
Why could split-brain patients pick up the correct object but not say its name?
- A
The cerebellum, not the cortex, controls left-hand movement.
- B
Severing the corpus callosum eliminates all visual processing in the left hemisphere.
- Ccheck_circle
Visual information from the left visual field is processed in the right hemisphere, which lacks language production but can guide the left hand.
- D
The left hemisphere processes left-visual-field input but cannot communicate with motor areas.
Explanation
Each visual field projects to the opposite hemisphere. The left visual field goes to the right hemisphere, which controls the left hand and recognizes objects but typically lacks the language production centers (Broca's area) found in the left hemisphere. With the corpus callosum cut, the right hemisphere cannot send the information to the left to be verbalized.