Chromatic subclasses of frog retinal ganglion cells: Studies using black stimuli moving on a monochromatic background

Abstract

The suprathreshold spectral responses of classes 1, 2, 3 and 4 neurons of the frog's retina to a black spot moving across monochromatic background fields of different wavelengths were determined under mesopic conditions by microelectrode recordings in the superficial layers of the optic tectum. This method revealed the existence of two subclasses of class 1 neurons, an a-type with a broad spectral response curve and a b-type with two maxima at 466 and 580 nm. Class 2 neurons also exhibited a- and b-types. In addition to the a- and b-subclasses, class 3 neurons exhibited a subclass with a narrow spectral response curve with a maximum at 500 nm. The exponent of the velocity functions of the neurons was found to be greater when the response originated from cones than when it originated from rods. After neuronal adaptation, the green rods and the neuronal elements connected to them recovered much faster than the red rods and cones.