Complexity analysis of magnetic stimulation at the acupoint of zusanli (St36) on EEG

Magnetic stimulation has become a very topical research area in brain studies because of its non-invasiveness, painlessness and security. It is well known that acupuncture has many varied physiologic effects on a number of functional systems of human subjects. In this paper, the EEG is recorded while the acupoint of Zusanli (St36) is stimulated by excitations of the same magnitude at different frequencies (0.5 Hz, 1 Hz, 3 Hz). Differences of EEG on the pre- and post-stimulation of the acupoint with magnetic field based on complexity analysis are reported. The data are analyzed with Sample Entropy (SampEn) and illustrated using Brain Information Mapping (BIM). The results indicate that the SampEn of all the data can be used to distinguish the magnetically stimulated states from the normal state. It is also observed that while all frequencies can induce increases of SampEn over the whole brain, with the most obvious changes being found in the temporal lobe. This observation is consistent with the responses of human to acupuncture. The change of SampEn has significant statistical significances with a stimulation at 3 Hz, even though the effect is less obvious with other frequencies, when compared with the brain activities in normal state (p < 0.05).