UC Berkeley

Phase slip and beat phenomena are ubiquitous in many forms of wave superposition. Likewise, it is trivially true that cumulative summation of white noise gives rise to “brown noise” (1/f2 power spectrum). We assume that the background electrocorticogram (ECoG) to a first approximation results from integration of innumerable action potentials by dendrites. This paper presents a simulation that relates these phenomena with cortical function. We report that cumulative summation of random numbers simulates resting ECoG, and that phase interference in the distributed frequencies of oscillation in bandpass-filtered brown noise gives null power spikes like those in the ECoG from test subjects. The null spikes coincide with the onsets of frames in which the spatial amplitude patterns are classifiable with respect to conditioned stimuli. We report similarity in the waveforms and amplitude distributions of null spikes upon filtering brown noise in bands corresponding to the theta, alpha, beta and gamma ranges in experimental and simulated ECoG. We estimate a threshold in null spike minimal amplitudes below which perceptual frames having gamma oscillations may recur at theta rates.