Roger Sperry (1913-1994)

Michael Gazzaniga (1939- )

Time period when Roger Sperry conducted and published his experiments on patients with corpus callosotomy (removal of corpus callosum bridging cortical hemispheres).

Together with Gazzaniga, Sperry showed that:

• patients are able to say what they saw on an images shown to the right side of the hemisphere
• when shown images on the left hemispheres, they were not able to verbalize what they saw, although they could draw it with their left hand
  • the contralateral hand was not able to perform such drawing though

These results served as evidence that the left hemisphere is required for language processing and that sensory information is transferred to contralateral motor units through the corpus callosum

---

However, it wasn’t always perfectly clean:

• Some patients improved over time
• Some showed partial transfer
• Results varied depending on how complete the split was

More recent research shows that hemispheric specialization is less rigid than originally implied, with substantial interhemispheric cooperation, residual communication, and distributed processing across both sides of the brain