Simulating cortical background activity at rest with filtered noise.

Phase slip and beat phenomena are ubiquitous in many forms of wave superposition. Likewise, it is trivially true that cumulative summation of individual random events gives rise to "brown noise" (1/f(2) power spectrum). This paper presents a simulation that relates these phenomena with cortical function. We report that phase interference in the distributed frequencies of oscillation in bandpass-filtered brown noise gives null power spikes like those in the electrocorticograms (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.