Optokinetic reactions of the beetle Chlorophanus are not only elicited by moving figures distinguishable against their backgrounds, but also from movements of randomly constructed patterns of shades from white through black (random functions). The evaluation of relative motions by the central nervous system is made in accordance with the correlation principle. The functional structure of perception, discussed in an earlier paper, describes the reactions to motions of random functions but does not explain the strength of optokinetic reactions which are released by moving sinusoidal patterns. In the following paper the frequency response functions of the filters are determined in such a way that the functional structure (Fig. 1) describes the reactions to both sinusoidal and randomly constructed light patterns (Fig. 3 and 4). Two results follow from the analysis: 1. The t;mc constants of the low pass filters are τF = 1,6 sec, τH = 0,03 sec. 2. The input filters cannot be of the differentiating type. Their frequency response function is proportional to the root of frequency. - The kinetics of the low pass filters can be explained on the basis of a first order linear differential equation which corresponds to a monomolecular chemical reaction. The frequency response functions of the input filters can only be explained by a partial differential equation describing processes of diffusion.
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