What is referred to as the "little brain" that coordinates movement and balance?

The term "little brain" is commonly used to refer to the cerebellum, which is a key structure located at the back of the brain. The cerebellum plays a crucial role in the coordination of voluntary movements, balance, and posture. It integrates sensory information from various parts of the body and uses this data to fine-tune motor activity, ensuring that movements are smooth and coordinated. This functionality is vital for tasks such as walking, running, and any activities that require precise motor control. The cerebellum also helps in learning motor skills, allowing individuals to improve and adapt their movements over time.

In contrast, other brain regions listed in the options have different functions. For example, the hippocampus is primarily involved in memory formation and spatial navigation, while the medulla controls autonomic functions such as breathing and heart rate. The limbic system is a complex set of structures that manage emotions, behavior, and certain aspects of memory but does not play a direct role in the coordination of movement. Thus, understanding the distinct functions of these brain structures helps clarify why the cerebellum is accurately described as the "little brain" responsible for coordinating movement and balance.