Changes of EMG activity patterns of extraocular muscles and the tonic control of eye position during the postnatal development of the rabbit.

The motor activity patterns of the rectus superior and obliquus superior extraocular muscles of the rabbit in response to static tilt stimulation were studied by electromyography in the unanaesthetized animal during postnatal development. During the first postnatal week the eye muscle activity showed a phasic pattern with continuous fluctuations of the activity level. The main postnatal decrease of the variability of EMG activity level occurs in the rabbit during the second week of life. Thereby, a constant tonic EMG activity of the extraocular muscles during static tilt stimulation was achieved from the third postnatal week onwards. The ability of stabilizing the eye position in space by this developmental process is an important prerequisite for the normal development of an effective visual orientation of the rabbit after the postnatal opening of the eyes.