What is the function of the trochlear nerve (CN IV)?

The trochlear nerve, or cranial nerve IV, plays a crucial role in the movement of the eye. Its primary function is to innervate the superior oblique muscle, which is responsible for controlling the downward and internal rotation of the eye. This movement is essential for various activities, such as looking downwards or towards the nose, which accommodates better vision during tasks like reading or writing.

Understanding the anatomical and functional aspects of the trochlear nerve can clarify its importance in coordinating eye movements and maintaining proper visual focus. It is distinctive compared to the functions of other cranial nerves involved in ocular movements or sensory and motor functions in the face, hence why this specific role of downward and internal eye rotation is correctly identified as the function of the trochlear nerve.