Peripheral pathway of eye muscle proprioception

Abstract

A cellular pool containing the soma of the afferent fibers from the spindles of the extraocular muscles has been found in the medial dorsolateral part of the semilunar ganglion of pig. In this regard there is no differences between pigs and sheep. But no responses to stretching extraocular muscles of the cat were found in the semilunar ganglion. In another group of animals, experiments were carried out in order to trace the course of the afferents from the eye muscle spindles to enter the brainstem. Responses to the stretch of the extraocular muscles were recorded from the trigeminal root in both sheep and pigs, but this was not the case for the root of the oculomotor nerve. Section of an ophthalmic branch of the trigeminal nerve immediately distal to the semilunar ganglion abolished such responses and was followed by degeneration of the spindles of the extraocular muscles in pigs and sheep. The ganglionic responses persisted after sectioning the connections between the oculomotor nerve and the ophthalmic branch at the level of the cavernous sinus. Intracranial section of the oculomotor nerve did not provoke degeneration of the eye muscle spindles. The conclusion was reached that the proprioceptive cells contained in the semilunar ganglion of pig and sheep have a central process which enters the brain stem through the trigeminal root, while the peripheral one courses through the ophthalmic branch and reaches the extraocular muscles.