Which structure connects the two brain hemispheres and carries messages between them?

The structure known for connecting the two brain hemispheres and facilitating communication between them is the corpus callosum. This thick band of neural fibers serves as a major pathway for information to travel from one hemisphere of the brain to the other. It integrates sensory, motor, and cognitive functions by allowing the left and right hemispheres to share information and work together seamlessly. For instance, if a task requires coordination between both sides of the body or the integration of verbal and visual processes, the corpus callosum plays a crucial role in coordinating these efforts.

The other structures mentioned do not serve this specific function. The cerebellum is primarily involved in coordinating motor control and balance, the thalamus acts as a relay station for sensory information before it reaches the cerebral cortex, and the hippocampus is essential for memory formation and spatial navigation. Thus, it is clear that the corpus callosum is uniquely suited for the task of connecting the two hemispheres of the brain.