What is the definition or description of: basal ganglia?

Basal ganglia: This is the term for several areas of the brain that work together as a functional unit: the striatum (caudate and putamen), the globus pallidus, the substantia nigra, and the subthalamic nucleus. The most well known function of the basal ganglia is voluntary motor control, but it is also involved in development of routine behaviors; eye movements; and cognitive and emotional functions.