Transcranial magnetic stimulation-induced global propagation of transient phase resetting associated with directional information flow.
Electroencephalogram (EEG) phase synchronization analyses can reveal large-scale communication between distant brain areas. However, it is not possible to identify the directional information flow between distant areas using conventional phase synchronization analyses. In the present study, we applied transcranial magnetic stimulation (TMS) to the occipital area in subjects who were resting with their eyes closed, and analyzed the spatial propagation of transient TMS-induced phase resetting by using the transfer entropy (TE), to quantify the causal and directional flow of information. The time-frequency EEG analysis indicated that the theta (5 Hz) phase locking factor (PLF) reached its highest value at the distant area (the motor area in this study), with a time lag that followed the peak of the transient PLF enhancements of the TMS-targeted area at the TMS onset. Phase-preservation index (PPI) analyses demonstrated significant phase resetting at the TMS-targeted area and distant area. Moreover, the TE from the TMS-targeted area to the distant area increased clearly during the delay that followed TMS onset. Interestingly, the time lags were almost coincident between the PLF and TE results (152 vs. 165 ms), which provides strong evidence that the emergence of the delayed PLF reflects the causal information flow. Such tendencies were observed only in the higher-intensity TMS condition, and not in the lower-intensity or sham TMS conditions. Thus, TMS may manipulate large-scale causal relationships between brain areas in an intensity-dependent manner. We demonstrated that single-pulse TMS modulated global phase dynamics and directional information flow among synchronized brain networks. Therefore, our results suggest that single-pulse TMS can manipulate both incoming and outgoing information in the TMS-targeted area associated with functional changes.
Department of Intelligent Interaction Technology, Graduate School of Systems and Information Engineering, University of Tsukuba Tsukuba, Japan ; Rhythm-based Brain Information Processing Unit, RIKEN BSI-TOYOTA Collaboration Center Wako, Japan ; Laboratory for Advanced Brain Signal Processing, RIKEN Brain Science Institute Wako, Japan.
Masahiro
M
Kawasaki
Rhythm-based Brain Information Processing Unit, RIKEN BSI-TOYOTA Collaboration Center Wako, Japan.
Yutaka
Y
Uno
Rhythm-based Brain Information Processing Unit, RIKEN BSI-TOYOTA Collaboration Center Wako, Japan ; School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University Yokohama, Japan.
Jumpei
J
Mori
Rhythm-based Brain Information Processing Unit, RIKEN BSI-TOYOTA Collaboration Center Wako, Japan ; School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University Yokohama, Japan.
Kenji
K
Kobata
Rhythm-based Brain Information Processing Unit, RIKEN BSI-TOYOTA Collaboration Center Wako, Japan ; Laboratory for Advanced Brain Signal Processing, RIKEN Brain Science Institute Wako, Japan.
Keiichi
K
Kitajo
electroencephalogram; information flow; oscillations; synchronization; transcranial magnetic stimulation; transfer entropy; transient phase resetting