Christian Guld

Representation of fovea in the striate cortex of vervet monkey, Cercopithecus ˦thiops pygerythrus

Abstract The representation of 0°–4° in the visual field was studied in the vervet monkey from averaged gross responses on the dorsolateral occipital lobe. The vertical meridian lay at the boundary between the striate and parastriate cortex 2 mm from the lunate and occipital sulci. The 1° semicircle and the horizontal meridian intersected at a small hollow. The horizontal and vertical meridians intersected at the far lateral boundary of the striate cortex, and the centre of foveola was represented within 2 mm from this point. On the parastriate strip, representation was a mirror image of that of the striate cortex and the latency of the response to visual stimuli was longer. The magnification factor was 12 mm/deg in the region representing 0.2°–8° from the centre of gaze.

Spectral and orientation specificity of single cells in foveal striate cortex of the vervet monkey, Cercopithecus aethiops.

1. The spectral sensitivity, orientation specificity and inhibitory surround of seventy‐three cells were studied in the vervet monkey. The eye was in the dark or illuminated with steady white or spectral light. The cells were in the striate cortex corresponding to the foveal representation. Nearly all the cells gave on‐ or on/off‐responses.

Contact lenses for animals used in vision research.

In investigations of vision where it is necessary to keep the eye open for many hours it is customary to use a contact lens to prevent the cornea from drying. The problem is to fit the inner radius of the contact lens to that of the cornea. Wiesel and Hube! (1966) used a keratometer to measure the cornea! radius. whereas other workers chose a suitable lens from a bank of lenses and corrected the eye to neutrality with correcting lenses in front of the eye. We are describing a method to determine the cornea! radius by retinoscopy and with contact lenses of known inner radius. The method and its theoretical basis are similar to those used in humans when ocular refraction was corrected with a glass contact lens with a thin fluid lens between it and cornea (Duke-Elder. 1970). The animals (vervet monkeys. Cercopithecus aethiops) were anesthetized with Ketalar@ and the pupil was dilated with I”/,: homatropine. The ocular refraction d, D (diopter) of the eye was measured by retinoscopy. Then a contact lens with inner radius r. and power d,D was placed on the eye and the refraction d2D of lens and eye was measured. In this case a thin fluid lens of unknown power d, lies between contact lens and cornea. Ocular refraction measured by retinoscopy gives the power of a lens which, when placed near to or on cornea. corrects the eye to neutrality. Thus a lens of power d,D corrects the eye, as does the summated power of the contact lens. the fluid lens and a lens of power dzD. For low powers we have therefore the equation d, = d, + d, + d2, from which the power of the fluid lens is