The mechanics of pigeon eye movements--are they like other vertebrates?

The lateral rectus muscle of the pigeon eye was driven by stimulation of the abducens nucleus. Eye rotation was measured with an opto-electronic movement detector. Eye position was linearly related to stimulation frequency in the range 40-110 Hz and saturated at frequencies above 250 Hz. Maximum eye velocity of 240 degrees/s was obtained with a stimulation frequency of 360 Hz. Stimulation with sinusoidally modulated pulse frequencies (40-110 Hz) over the modulation frequency range 0.01-6.0 Hz were used to determine the gain and phase relationships of the oculomotor system. The response approximates a first order low pass frequency model with a characteristic frequency of 0.45 Hz at high frequencies. There is an additional phase lag equivalent to a time delay of 9.8 ms. The results are compared with similar experiments performed on the dogfish and cat oculomotor systems.