Possible Interactions Between Gravi-Receptors and Semicircular Canals in the Habituation of Vertical Nystagmus in Parrots

Abstract

Horizontal ocular nystagmus from restrained birds was habituated in a directionally specific fashion by means of repeated angular accelerations. Substantial response recovery was evident following two weeks of rest. Vertical nystagmus was similarly habituated in a separate group of birds which were positioned so that vertical semicircular canals were in the plane of rotation. By changing the position of these birds 180° after the habituation trials, the same set of vertical canals could be stimulated but with the oto-liths and other gravi-receptors oriented differently. Habituation was relatively specific for the direction of nystagmus repeatedly elicited and for the head and body position maintained during habituation trials. A dynamic interaction between gravi-receptors and the semicircular canals was suggested as a possible feature of nystagmic habituation.