Split-brain patients and the left visual field
A split-brain patient sees an image of a key flashed only to his left visual field. He says he saw nothing, but his left hand picks out a key from objects hidden behind a screen. Why?
Answer A: explanation for every choice
A
Correct. The left visual field projects to the right hemisphere. Without the corpus callosum, that information can't reach the left hemisphere's language areas.
B
Images in the left visual field go to the right hemisphere, not the left.
C
With the corpus callosum cut, the image reaches only one hemisphere. The correct hand choice shows memory was intact.
D
In split-brain patients, the corpus callosum has been severed.
TakeawayLeft visual field → right hemisphere → left hand, usually without speech.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID ps164.