Somatotopic localization of the eye muscle afferents in the semilunar ganglion.

In the medial dorsolateral portion of the semilunar ganglion of curarized and anaesthetized lambs a cellular pool has been identified which contains the perikarya of the first-order neurons of the eye muscle proprioception. Responses to moderate manual stretch of individual eye muscles were recorded by means of tungsten microelectrodes, from single units of the ganglion. They were of the type induced by muscle spindle excitation. Such responses showed a somatotopic localization. The superior rectus and the superior oblique muscles were represented in the most dorsal layers of the ganglion, while the inferior rectus and the inferior oblique muscles projected on the most ventral portion of the pool. The medial and the lateral recti were represented in the medial and lateral parts and occasionally wedged themselves between the cells innervating the superior and the inferior muscles. Thus a somatotopic arrangement of the eye muscle proprioception has been demonstrated for the first time in the semilunar ganglion.