The Basic Brainstem Circuit for the VOR when the head turns to the right.
consisting of 1) vestibular n.(vn), 2) motoneurons (in the VI and III nuclei), and 3) muscles (lateral rectus, lr, and medial rectus, mr).
The direct path, by itself, is not enough. Why?
During the head rotation there is a phasic response seen in vestibular afferents (sense how fast you rotate), which rotates the eyes to the left.
After the head rotation this phasic activity stops.
This presents a problem: the eye would drift back to center because the muscles need a tonic input to keep the eye rotated.
