Final answer:
Information from the opposite hemisphere crosses the corpus callosum, a structure that allows the two brain hemispheres to communicate. Additional crossing occurs in structures like the optic chiasm and the brainstem for visual information and neural connections, respectively.
Step-by-step explanation:
The information coming from the opposite hemisphere has to cross the corpus callosum. This structure is a thick band of neural fibers, consisting of about 200 million axons, which allows the two hemispheres of the cerebrum to communicate with each other.
It connects each point in a hemisphere to the mirror-image point in the opposite hemisphere, enabling the sharing of processed information. When the corpus callosum is severed, as mentioned in point (d), the ability of the left and right hemispheres to communicate is lost.
In addition to the corpus callosum, the optic chiasm is another important structure where information must cross sides. Here, contralateral visual field information from the lateral retina projects to the ipsilateral brain, while ipsilateral visual field information decussates at the optic chiasm to reach the opposite side of the brain.
Lastly, point (c) and (d) refer to neural connections being switched in the brainstem, where descending and ascending connections from one hemisphere of the brain are transmitted to the opposite side of the body.