The procerus muscle is a small pyramidal muscle in the glabella. It is involved in facial expressions such as frowning and those associated with attentional control, and it indirectly helps shield the eyes from bright light. Because it contributes to wrinkle formation on the nasal bridge, it is often targeted in non-surgical facial rejuvenation treatments, such as botulinum toxin injections. Procerus is Latin, meaning tall or extended.