What part of the brain coordinates muscle groups for complex motor tasks?

The cerebellum is crucial for coordinating muscle groups during complex motor tasks such as balance, posture, and skilled movements. It integrates sensory information related to the position of body parts and adjusts motor output accordingly to ensure fluid and accurate movement. The cerebellum also plays an essential role in learning motor skills, allowing individuals to refine their movements through practice.

In contrast, while the cerebrum is responsible for higher cognitive functions and voluntary motor activity, it does not primarily coordinate muscle groups. The brainstem is involved in basic life functions and some reflex actions rather than complex motor coordination, and the corpus callosum mainly facilitates communication between the left and right hemispheres of the brain. Thus, the cerebellum stands out as the primary area for coordinating complex motor tasks.