Internuclear ophthalmoplegia. Information travels from the sixth nerve nucleus (VI) to the ipsilateral lateral rectus muscle (LR) and, via the medial longitudinal fasciculus (MLF), to the contralateral third nerve nucleus (III) and so on to the contralateral medial rectus (MR) to make both eyes turn to the side of the stimulating sixth nerve nucleus. A lesion blocking the path between the ipsilateral sixth nerve nucleus and the contralateral third nerve nucleus results in an internuclear ophthalmoplegia.