The Fractal Features of the Background Activity of Neurons in the Auditory Center of the Frog Midbrain

Resumo

Abstract—Statistics were obtained for background firing activity recorded from several neurons of the auditory center of the midbrain (semicircular torus) in the common frog. The methods were those used to analyze the temporal flow of fractal point processes. Most neurons showed a power-law increase in the variance-to-mean ratio (Fano factor) of pulse number with the time window increasing from hundreds of milliseconds to several tens of seconds, although cells whose background firing activity was close to random were also observed. A method based on the registration of local features (the Allan factor as a function of the same time window) confirmed the fractal properties for many cells. A power-law growth of the Allan factor usually began at large time windows. The third method of fractal analysis (the Hurst index) also argued in favor of the randomness and fractality of background firing activity. The relationships with other statistics of random point processes were analyzed for the fractal characteristics. A comparison with data obtained for neurons of the medulla oblongata indicated that the variability of firing activity slight increases along the auditory pathway.