Studies On Habituation Of Vestibular Reflexes: I. Effect of Repetitive Caloric Test

Abstract

The phenomenon of habituation to repetitive caloric stimulation was investigated in cats. The study included acquisition, retention and transfer of the response decline in nystagmic reaction. Acquisition of habituation was obtained by repetitive calorization of right and/or left ears with hot and/or cold water. The rate of response decline was rapid with the initial irrigations and then tended to level off. The extent of response decline differed among animals, ranging from moderate reduction to complete extinction. In the cat, habituation may be retained after three weeks of rest; however, in several animals, recovery of normal caloric responses occurred after a few days. Transfer of habituation occurs, provided the nystagmus is provoked in the same direction as that which was habituated. The evidence supports the opinion that the neural mechanism underlying habituation of vestibular reflexes is a central process. The locus of this mechanism remains unknown. The practical and theoretical implications of this phenomenon are briefly discussed.