Beats as the origin of slow fluctuations in the brain's default-mode network

Recently, slow synchronizations in the blood oxygen level dependent (BOLD) signals of the brain at a rate lower than 0.1 Hz have been observed by fMRI under dozing rest conditions. This phenomenon is referred to as the “default-mode brain network.” Many cortex neurons in the brain seem to be quiet in this situation, but fMRI implies that many regions maintain high-level activity even though fluctuations in BOLD signals are very slow. However, there are typical brain wave synchronizations — the well-known “rhythms” — that emerge under various conditions. Here we show the relationship between the slow fluctuation and the well-known rhythms by using a new complex neural network model of the default-mode brain network. Then, beats are implied to play an important role on the origin of the slow fluctuation.