Optic chiasm
The place at the base of the brain where some of the fibers from each eye cross to the other side. In split-brain animal studies it was cut down the middle, so that what one eye saw reached only the hemisphere on the same side.
Some of the fibers from each eye cross to the opposite hemisphere at the optic chiasm. Roger Sperry's laboratory used cats and monkeys in which this crossing had been cut down the middle, so that what one eye saw reached only the hemisphere on the same side[1].
After being trained with one eye covered to tell two shapes apart, animals with only the chiasm cut still told them apart when the cover was moved to the other eye. If the corpus callosum and anterior commissure were cut as well, the animals behaved as if they knew nothing of the task when it was shown to the untrained eye[1][2].
Related terms
- Split brainA brain whose corpus callosum and other connections between the halves have been cut, so that the right and left halves work separately. Animal studies in the 1950s and patient studies from 1962 showed that what one half saw or learned, the other did not know.
- Corpus callosumThe thick bundle of nerve fibers that joins the right and left halves of the cerebrum. Surgeons began cutting it in 1940 to treat epilepsy, and in the 1960s researchers began testing the two halves of such patients separately.
Sources
- M. S. Gazzaniga, “The split-brain: rooting consciousness in biology,” Proceedings of the National Academy of Sciences 111(51), 18093–18094 (2014).
- R. E. Myers and R. W. Sperry, “Interhemispheric communication through the corpus callosum: mnemonic carry-over between the hemispheres,” AMA Archives of Neurology and Psychiatry 80(3), 298–303 (1958).