MONOCULAR EYE MOVEMENTS OF PIGEON

The monocular eye movements of both restrained and partially restrained pigeons have been measured by means of a mirror attached to the edge of the cornea. The principal observations may be summarized under the following categories. Flicks, or eye movements which bring about a rapid change of fixation, are found to occur only in response to sudden and unexpected motion of a visual stimulus and are rarely observed under the quiescent conditions of a darkened room. Drifts, which are slower movements of the eye between fixation points, occur at velocities of about 1-5 deg per sec and are stimulated by object motion. Tremor motion is of extremely low amplitude and is unlikely to serve any visual function. Oscillations occur in short bursts at frequencies of about 30 Hz and amplitudes of several degrees. The evidence indicates that this eye movement is normally executed during a blink and it is probable that it performs a polishing action on the cornea in conjunction with the nictitating membrane. The observations lead to the conclusion that although the range of rotational motion available to the pigeon is less than in man, it nevertheless possesses a well developed and precisely controlled oculomotor system which appears in some respects to out-perform our own. © 1969.