Quick Answer. The function of motor neurons is to release the neurotransmitter acetylcholine, which are released at a junction known as the neuromuscular junction, that bind to postsynaptic receptors, causing the muscle fiber to respond and result into a muscle movement.
The frontal lobe is what really sets us apart from animals, which controls one important aspect of humans: Self awareness. The thinking in terms of I am.. Animals don't do that. (although they DO have sex for pleasure.
The only thing that sets Device apart, albeit slightly, is the music and that's why they pursue the added vocals of other artists in an effort to be set apart from Disturbed. Draiman does have great pipes but that's about all now.