DISCRIMINATION OF HORIZONTAL AND VERTICAL PLANES OF POLARIZED LIGHT BY THE CEPHALOPOD RETINA

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Abstract
[long dash]The ERG (electroretinogram) of the octopus and squid was studied when a plane of polarized light was rotated. The direction of electric vector was expressed by the angle of deviation from the standard direction of the retina, the horizontal axis of the retina. There was no differential response with respect to the simple rotation of the polaroid. If the retina was pre-illuminated by polarized light of which e vector was at 45[degree], still no differential response was noted. Pre-adaptation at around 0[degree] (angle of deviation of e vector of adapting light from the standard direction was less than 45[degree]) caused maximum suppression (minimum response) at 0[degree] and 180[degree], and minimum suppression (maximum response) at 90[degree] and 270[degree] of test lights. Pre-adaptation at around 90[degree] (e vector was between 45[degree] and 135[degree], except at 45[degree] and 135[degree]) gave the opposite result. These results suggest that in the cephalopod retina there are only 2 sensitive planes which are maximally sensitive to either the horizontal or vertical vector-component of the incident light. These sensitive planes could well be analyzers which can discriminate e vectors between horizontal and vertical but not between 45[degree] and 135[degree]. The morphological basis was considered and it was concluded that the horizontal-vertical organization of the rhabdomeres is the mechanism for polarization analysis.

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