In placental mammals, 800 million axons {corpus callosum}| connect left and right cerebral hemispheres [Aboitiz et al., 1992] [Kretchmann and Weinrich, 1992].
Brain also has smaller connections between hemispheres.
processing
Corpus-callosum posterior splenium relays visual information from left visual field to speech area.
damage
Cutting corpus callosum causes epileptic-like brain firing.
split brain
Cutting all connections between left and right hemispheres can show psychological functions performed by hemispheres. Cutting only corpus callosum makes no change, because other connections can still carry signals.
After cutting, people cannot match unseen object felt by the hand to seen object felt by right hand. Two separate experiences or discriminations can happen simultaneously.
Both hemispheres know words, pictures, and metaphorical relationships. Both hemispheres are aware.
Will, consciousness, motivation, and coordination are only slightly depressed, except for short concentration lapses. Perception, object location, and space orientation stay the same.
Either hemisphere can activate, depending on task, sex, age, handedness, education, and training.
Over time, functions performed by hemispheres become more alike.
brainstem
Brainstem dismay, embarrassment, or amusement feelings, generated in one hemisphere by threat, risk, or teasing perceptions, can cause body movements, emotions, attention, and orientation.
Biological Sciences>Zoology>Organ>Nerve>Brain>Cerebrum
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Date Modified: 2022.0224