By the end of the preschool period, the , a bundle of nerve fibers that connect the two hemispheres of the brain, becomes considerably thicker

corpus callosum

Explanation:

Corpus callosum is bundle of nerve fibers that connect the two hemispheres of the brain. It becomes considerably thicker during preschool period.

The corpus callosum is a Latin word which means tough body. On the other hand, callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain.

The corpus callosum can only be found in placental mammals.

It goes from part of the longitudinal fissure, then connects the left and right cerebral hemispheres, enabling communication between them.

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