Extraocular proprioceptive signals affect ocular motor activity neither directly nor parametrically in the presence of optokinetic or vestibular stimulation in the frog

Summary Direct and parametric effects of stretch receptors in the extraocular muscles on abducens nerve activity were investigated in the unanesthetized immobilized frog. Horizontal passive rotations of one eye in the physiological range (±5°) did not elicit responses in the activity of abducens nerve on either side; however, larger rotations or pull of one eye evoked long latency direction-unspecific responses simultaneously in both nerves. When the animal was stimulated vestibulary in the horizontal plane with sinusoidal or constant acceleration, abducens activity was not altered in correlation to passive eye movements in the physiological range. Similarly, the activity of either nerve evoked by simultaneous or preceding optokinetic stimulation of one eye with constant pattern velocity was not modified by passive rotation of the contralateral eye.