What are the basal ganglia? The basal ganglia(or basal nuclei)are a group of nuclei of varied origin(mostly telencephalic embryonal origin, With some diencephalic and mesencephalic elements)in the brains of vertebrates that act as a cohesive functional unitWhat are the basal ganglia? The basal ganglia (or basal nuclei) are a group of nuclei of varied origin (mostly telencephalic embryonal origin, with some diencephalic and mesencephalic elements) in the brains of vertebrates that act as a cohesive functional unit