Signal processing and modelling of the response of crayfish photosensitive ganglion

The terminal abdominal ganglion of the crayfish acts as a photoreceptor. When this sensory receptor is illuminated, the crayfish will walk randomly into a region of subdued illumination. In the 1950´s, Lawrence and his group has recorded the response of the crayfish for a step change in light intensity with intra- and extra-cellular electrodes. As it is difficult to produce an impulse of light,they recorded the response with a step change in light. The mid-range, pulses, the pulses of Interest, were shaped to produce constant-size pulsar, then integrated to produce a voltage whose level corresponds to the instantaneous output frequency of the neuron population. In this paper, an attempt is made to process the recorded data which contains signal corrupted with noise. The data is first digitized and than processed by Fourier transform in order to obtain relative frequency of the signal and noise. This has revealed that the signal frequency is below 3 Hz and the noise frequency is above this frequency. Therefore the noisy data is processed through a low-pass filter and the noise-free signal is obtained. A modal to fit the noise-free response is constructed. The response of the model in compared with that of the noise-free signal. It is found that they are in good agreement