The Random Walk System

Abstract

The crayfish has a pair of ordinary cephalic eyes capable of spatial perception. In addition, it possesses a primitive photosensitive tail ganglion, A₆, of the ventral nerve cord, which even in the absence of normal visual input, permits light avoidance behavior in the form of an aversive walk. This response induces the animal to seek out and remain in dark environments, providing that no overriding stimuli exist [27, 41, 61, 63]. In order to study this response it is useful to scrutinize the entire sequence of signals: (a) light energy, (b) ascending nerve impulses from photoreceptor to brain, (c) descending nerve impulses from brain to thoracic ganglia, (d) motor nerve impulses, (e) muscular contraction. A first stage of our research is to record the nerve signals along the path of the random walk response [14–16, 30, 36, 55].