Contrast induced zones as the basis of optomotor memory in the crab, Pachygrapsus

Abstract

A theory that optomotor memory involves the formation of limited black- and white-sensitive zones within the retina is presented. These zones would be formed due to the presence of any black-white border within the visual field. They adjoin each border with a black-sensitive zone on its white side, and a white-sensitive one on its black side (Fig. 1). This theory is confirmed by experimental results indicating that 1) only black-white reverses occurring within 3 to 4.5° of a former border position affect the size of memory responses (Fig. 3, 7), 2) black-white reverses within zones result in memory responses even though the original borders have not been displaced, and 3) unless a black-white reversal occurs within some zone no response will occur, even though displacement of the originally present border is obvious (Fig. 7). The stimulating effect of making a black-sensitive zone black is greater than making a white-sensitive zone white (Fig. 5). From the results of these and previous experiments it is inferred that memory is peripherally located. Other physiological aspects of the process are also considered.

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