Iv. The Reaction in Animals With Unilateral Lesions in the Brain Stem

Abstract

Previous reports have described the galvanic reaction in guinea pigs with unilateral labyrinthectomy and with unilateral destruction of the eighth nerve.1 It has been shown, contrary to the findings in human subjects reported by Blonder,2 that the reaction is still elicitable after destruction of the labyrinth, although requiring a considerably stronger current. This is in agreement with the findings reported by Blau 3 and others, including those in the recent report of Northington and Barrera.4 After destruction of the eighth nerve the galvanic falling reaction could still be elicited, but, again, a stronger current was required than for normal animals. Dohlman,5 Northington and Barrera 4 and others have found that galvanic nystagmus cannot be elicited after destruction of the eighth nerve.The nervous structures involved in the galvanic falling reaction seem, logically, to include: (1) the labyrinth; (2) the vestibular division of the eighth nerve; (3) the vestibular nuclei, and (4) the descending pathways from the vestibular nuclei, including the vestibulospinal tract and the medial longitudinal fasciculi. Any explanation why a pathway so constituted should be responsible for an almost constant falling reaction toward the anode and away from the cathode when galvanic current is allowed to flow through the ear is, so far as I know, still lacking. Since