Some people have had the communication between the two halves of their brain severed. It's called callosal syndrome. It leads to some very interesting effects.

Your brain is kind of hooked up backwards to your body. The left half controls the right side and vise versa.

When these people are shown an image only in the left half of each eye's visual field, it only goes to the right side of their brain through the optic nerves.

But your speech center is on the other side (the left). SO THEY CANNOT NAME THE THING! Like, they know what it is intellectually, but they can't produce the word until the left side of their brain gets to see it.