What structure connects the two hemispheres of the brain?

The structure that connects the two hemispheres of the brain is the corpus callosum. This large bundle of nerve fibers is responsible for facilitating communication between the left and right hemispheres, allowing for the integration of sensory, motor, and cognitive functions. The corpus callosum plays a critical role in coordinating activities that require both hemispheres to work together, such as language, movement, and problem-solving.

In the context of the other options, the thalamus serves primarily as a relay station for sensory information and does not connect the hemispheres. The corpora quadrigemina is involved in visual and auditory reflexes but is not responsible for interhemispheric communication. The hippocampus is crucial for memory formation and spatial navigation, but it does not connect the hemispheres either. Thus, the corpus callosum is uniquely suited for linking the two hemispheres, making it the correct answer.