A Comparative Study on the Dynamic EEG Center of Mass with Different References.

Yun Qin,Yongxiu Lai,Hongchuan Xiong,Hao Zhu,Fali Li,Tao Zhang,Xiuwei Xin

doi:10.3389/fnins.2017.00509

Abstract

One of the most fundamental issues during an EEG study is choosing an available neutral reference. The infinity zero reference obtained by the reference electrode standardization technique (REST) has been recommended and used for its higher accuracy. This paper examined three traditional references, the average reference (AR), the linked mastoids reference (LM), and REST, in the study of the EEG center of mass (CM) using simulated and real ERPs. In the simulation, the relative error of REST was the smallest among the references. As for the ERP data with the visual oddball paradigm, the dynamic CM trajectory and its traveling velocity obtained by REST characterized three typical stages in spatial domain and temporal speed metrics, which provided useful information in addition to the distinct ERP waveform in the temporal domain. The results showed that the CM traveling from the frontal to parietal areas corresponding to the earlier positive components (i.e., P200 and P250), stays temporarily at the parietal area corresponding to P300 and then returns to the frontal area during the recovery stage. Compared with REST, AR, and LM not only changed the amplitude of P300 significantly but distorted the CM trajectory and its instantaneous velocity. As REST continues to provide objective results, we recommend that REST be used in future EEG/ERP CM studies.

Highlights

Electroencephalogram (EEG) denotes the spatiotemporal dynamic process of the encephalic neural activities
The average reference (AR) had a larger error in the anterior areas, while the linked mastoids reference (LM) reference had a larger error in the posterior areas
The reference effect on simulated data as well as on ERP data measured by center of mass (CM) trajectory and CM traveling velocity was examined

Summary

Introduction

Electroencephalogram (EEG) denotes the spatiotemporal dynamic process of the encephalic neural activities. The choice of reference influences both the spatial and temporal aspects of the EEG, which is one of the most fundamental issues in EEG analysis and interpretation. For the scalp distribution of the EEG at a set time point, different reference choice will introduce a constant value at all locations, similar to raising or lowering the water level of a landscape, without changing the shape (Pascualmarqui and Lehmann, 1993; Geselowitz, 1998). When the reference site on the body surface is active, the EEG dynamic process may be distorted due to the temporal bias of the reference signal. Research teams are searching for the best available reference option for cross-study comparison (Kayser and Tenke, 2010; Nunez, 2010)

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Discussion

Conclusion