Central nystagmus. III. Functional correlations of mesodiencephalic nystagmogenic center

Abstract

Transverse cuts at various levels of the rabbit brain stem have different effects on vestibular nystagmus and on central nystagmus elicited by electrical stimulation of the mesodiencephalic nystagmogenic area. While transections rostral to the sensitive region enhance both, probably by elimination of inhibitory influences from cortex or retina, transections caudal to this region, but rostral to the colliculi, abolish central nystagmus only. Transections at the level of the inferior colliculus abolish vestibular nystagmus only, while intermediate cuts may eliminate either response. When central nystagmus alone survives, its character is changed in a specific way indicating the important role of the vestibular nuclei in normal central nystagmus. These observations lead to an approximate localization of the common substrate for conjugate eye movements involved both in central and vestibular nystagmus. Longitudinal cuts through the posterior commissure provoke a temporary disconjugated nystagmus not described hitherto.