Which structure connects the two hemispheres of the brain?

The corpus callosum is the structure that connects the two hemispheres of the brain. It is a thick band of nerve fibers that facilitates communication between the left and right hemispheres, allowing for the integration of cognitive, sensory, and motor functions. By serving as the primary pathway for interhemispheric communication, the corpus callosum plays a crucial role in coordinating activities that involve both sides of the body and processing information that involves both hemispheres.

The cerebellum, while important for balance, coordination, and fine motor skills, is not responsible for connecting the hemispheres. The brainstem is essential for regulating basic life functions such as breathing and heart rate, but it does not connect the two halves of the brain. The thalamus acts as a relay station for sensory information and is a key player in the regulation of consciousness and sleep, but it does not function as the connector between the hemispheres. Thus, the unique role of the corpus callosum makes it the correct answer for this question.