The spectral sensitivity of dark‐adapted cats

Abstract

By the method of electrophysiology Granit (1945) has obtained evidence in the cat's eye of the presence of activity of specialized mechanisms which exhibit selective sensitivity to wave-length. Using this procedure, a great deal of information on the spectral distribution of sensitivity of receptor organs in different states of adaptation has been accumulated.The spectral sensitivity curve is likely to correspond to a reaction of the retina which manifests itself as a measurable electrical response; however, from a physiological point of view, these responses provide information only about retinal activity. The electrical method cannot tell us what the animal actually sees, because the function of seeing involves more than just the generation of electrical impulses. It is the interpretation of these impulses by the higher centres of the living animal which constitutes 'seeing' in its proper sense. In the present experiment, the 'training method' has been employed to obtain quantitative data on the sensitivity of the dark-adapted cat to lights of different wave-length. It is the aim of this experiment to determine to what extent the action potentials found in the cat's retina for this function do, in fact, correspond to the process of 'seeing' in the lving animal. METHOD Discrimination apparatusIn this apparatus the stimulus lights of different intensities were projected on a milk-glass screen, situated in each of the two doors of a Y-shaped discrimination apparatus. The animal made its choice by pushing open one of the doors and obtaining a food reward behind the one bearing the positive stimulus. A detailed description and a diagram of the apparatus are given in an earlier publication (Gunter, 1951a). ControlsThe precautions taken to ensure equality of olfactory stimulation, and the tests for prevention of light-adaptation and for light.tightness of the apparatus, were the same as those carried out previously

Conditioned suppression as a psychophysical technique for the cat

“…The average error across days, wavelengths, and Ss was ± .29 log units. The overall scotopic luminosity function determined by this method agreed very well with the behavioral determinations of other investigators (Gunter, 1952;LaMotte & Brown, 1970) and will be discussed elsewhere (Loop & Berkley, in preparation). The major advantage of the present method was that only nine threshold determinations (720 trials) were required at each point.…”

“…The major advantage of the present method was that only nine threshold determinations (720 trials) were required at each point. Gunter (1952) employed over 3,500 trials at each point, and LaMotte and Brown (1970) required 24-42 threshold determinations per point for their scotopic luminosity function.…”

The Purkinje shift in cat: extent of the mesopic range

“…Granit, 1943Granit, , 1945Granit, , 1955Gunter, 1952Gunter, , 1954Weale, 1953;Barlow, Fitzhugh & Kuffler, 1957a;Barlow & Levick, 1968). It is established that the shift is primarily dependent upon a single class of cones (556 nm) and a single class of rods (500 nm) in the retina (Daw & Pearlman, 1969;Pearlman & Daw, 1970;Andrews & Hammond, 1970 a, b;Hammond, 1971).…”

Chromatic sensitivity and spatial organization of cat visual cortical cells: cone‐rod interaction

“…It is inferred that cortical fields are compounded essentially by convergent input from geniculate cell field-centres. INTRODUCTION In cat the Purkinje shift from 556 nm (photopic) to around 500 nm (scotopic) is well established both behaviourally and from retinal neurophysiology (Granit, 1943(Granit, , 1945(Granit, , 1955Gunter, 1952Gunter, , 1954Weale, 1953;Barlow, Fitzhugh & Kuffler, 1957a). The increment threshold measurements of Daw & Pearlman (1969) for single units in LGN, optic tract and optic radiations are indicative of a single class of cones in the retina (peak 556 nm), and a single class of rods (500 nm).…”