A Behavioural Test of Rod-Red Cone Convergence in the Goldfish Retina
The experiments described here represent a behavioural test of the physiological model of the goldfish retina, proposed by Raynauld (1972), in which rods and long wavelength sensitive cones are connected by similar, perhaps identical, neural pathways to the ganglion cells. The model was suggested by Raynauld’s observation that the ganglion cells responded in the same way to long wavelength light at photopic levels of illumination as they did to any wavelength at scotopic levels. This was confirmed by Beauchamp and Daw (1972), and supported by the anatomical report of Scholes and Morris (1973). If we can accurately predict behaviour from the cellular electro-physiology, then we can be more confident that the small number of ganglion cells that have been sampled by microelectrodes are representative of the tens of thousands whose axons carry the output of the entire retina. Moreover, a test of the model bears on current theories of underwater vision (Lythgoe, 1968; Easter, 1974), in which the long wavelength end of the spectrum is assigned special importance because of the higher contrast available there (Duntley, 1962). Perhaps the convergence of rods and red cones represents a physiological exploitation of this physical fact.
KeywordsGanglion Cell Absolute Threshold Opponent Color Entire Retina Goldfish Retina
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