What structure connects the two hemispheres of the cerebellum?

The cerebellar vermis is the structure that connects the two hemispheres of the cerebellum. It is a narrow, worm-like structure located in the midline of the cerebellum, playing a crucial role in coordinating and integrating sensory and motor functions across both hemispheres. The vermis helps in the regulation of posture, balance, and the coordination of voluntary movements by ensuring that both sides of the body work together harmoniously.

In contrast, the cerebral cortex is involved in higher-level processing and is located atop the cerebrum, not connecting the cerebellar hemispheres. The brainstem is a critical structure for many essential life functions and connects the brain and spinal cord, but it does not specifically connect the cerebellar hemispheres. Similarly, the basal ganglia, which play a role in movement regulation, are situated within the cerebrum and do not have a direct role in connecting the cerebellar hemispheres. Thus, the correct answer highlights the unique and specific anatomical connection of the cerebellar vermis in the cerebellum.