The Maturation of Eye Movement in the Cat
The aim of this report was to verify whether maturation can influence eye movement in the alert kitten. The experiments were carried out on 5 adult cats and on 5 kittens aged 35–50 days. The maturation of visuomotor behaviour (Van Hof 1976) and of the vestibular-ocular reflex (Flandrin et al. 1979) is incomplete at this age. Animals were operated under general anaesthesia one week before the experiment to allow painless fixation of the head. The experiments were executed in a darkened cage. To define the behavioural state EEG and EMG were recorded. Horizontal and vertical components of eye movement were recorded by a modified Robinson’s search coil using the magnetic field technique. Briefly, the coil was inserted in a suction contact lens that was placed on the ocular globe on the day of the experiment. We have found that in awake kittens the spatio-temporal pattern develops in a prevailing vertical plane; on the contrary, in the cat it is developed in a horizontal plane. The vertical orientation reminded us of what we had found in REM’s episodes in kittens as well as in cats (Bon et al. 1983). Generally, a rapid eye movement is followed by a fixation. In the present experiment we have computed the percentage of movements followed by fixation. In the kitten, the percentage was low (26.7%), in the cat, it was higher (68.7%).