Which muscle is responsible for wrinkling the forehead?

The muscle responsible for wrinkling the forehead is the frontalis. This muscle is located in the forehead region and is part of the occipitofrontalis muscle group. When the frontalis contracts, it elevates the eyebrows, which in turn causes the skin of the forehead to wrinkle. This action is typically associated with expressions of surprise or curiosity. The frontalis is unique in its function as it specifically affects the forehead area, making it the primary muscle involved in creating those characteristic forehead wrinkles.

In contrast, the orbicularis oculi primarily functions around the eyes, facilitating movements such as blinking and squinting. The orbicularis oris is focused around the mouth, playing a key role in movements like kissing and speaking. Meanwhile, the zygomaticus major assists in facial expressions related to smiling rather than affecting the forehead area. Therefore, the frontalis is the correct choice for this specific action.