The mathematical basis of population rhythms in nervous and neuromuscular systems

The mechanism underlying rhythmical aggregate activity of a population of neural or neuromuscular elements is examined in this report. By making use of the spectral properties of stochastic processes (Papoulis, 1965), it is shown that such population rhythms are the inevitable effect of the rhythmical activities of the individual elements, irrespective of the phase relations of the latter. This result applies to both "discrete" signals, such as spike trains, and "continuous" ones, such as membrane potential fluctuations. It has implications regarding the generation of common physiological rhythms and the preservation of rhythms when converging activity of one of the above two types is transformed into activity of the other type.