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In the case of auditory information, both hemispheres receive input about what each ear hears. However, information first goes to the opposite hemisphere. If the left ear hears a sound, the right hemisphere registers the sound first.

The fact that the brain’s hemispheres communicate with opposite sides of the body does not affect most people’s day-to-day functioning because the two hemispheres constantly share information via the corpus callosum. However, severing the corpus callosum and separating the hemispheres causes impaired perception.

Split-Brain Studies

If a researcher presented a picture of a Frisbee to a split-brain patient’s right visual field, information about the Frisbee would go to his left hemisphere. Because language functions reside in the left hemisphere, he’d be able to say that he saw a Frisbee and describe it. However, if the researcher presented the Frisbee to the patient’s left visual field, information about it would go to his right hemisphere. Because his right hemisphere can’t communicate with his left hemisphere when the corpus callosum is cut, the patient would not be able to name or describe the Frisbee.

The same phenomenon occurs if the Frisbee is hidden from sight and placed in the patient’s left hand, which communicates with the right hemisphere. When the Frisbee is in the patient’s left visual field or in his left hand, the patient may not be able to say what it is, although he would be able to point to a picture of what he saw. Picture recognition requires no verbal language and is also a visual-spatial task, which the right hemisphere controls.

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