A Comparative Study of Average, Linked Mastoid, and REST References for ERP Components Acquired during fMRI

Abstract

In simultaneous electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) studies, average reference (AR), and digitally linked mastoid (LM) are popular re-referencing techniques in event-related potential (ERP) analyses. However, they may introduce their own physiological signals and alter the EEG/ERP outcome. A reference electrode standardization technique (REST) that calculated a reference point at infinity was proposed to solve this problem. To confirm the advantage of REST in ERP analyses of synchronous EEG-fMRI studies, we compared the reference effect of AR, LM, and REST on task-related ERP results of a working memory task during an fMRI scan. As we hypothesized, we found that the adopted reference did not change the topography map of ERP components (N1 and P300 in the present study), but it did alter the task-related effect on ERP components. LM decreased or eliminated the visual working memory (VWM) load effect on P300, and the AR distorted the distribution of VWM location-related effect at left posterior electrodes as shown in the statistical parametric scalp mapping (SPSM) of N1. ERP cortical source estimates, which are independent of the EEG reference choice, were used as the golden standard to infer the relative utility of different references on the ERP task-related effect. By comparison, REST reference provided a more integrated and reasonable result. These results were further confirmed by the results of fMRI activations and a corresponding EEG-only study. Thus, we recommend the REST, especially with a realistic head model, as the optimal reference method for ERP data analysis in simultaneous EEG-fMRI studies.

Open- and Closed-Skill Exercise Interventions Produce Different Neurocognitive Effects on Executive Functions in the Elderly: A 6-Month Randomized, Controlled Trial

“…Lastly, the ERP recordings in the present study were referred to a linked mastoid reference, and this is not an ideal zero reference, and thus the task-related effect could have been impacted by this, and a potential bias produced (Yao, 2001 ). However, the adopted reference did not change the topography map of the P300 components (Yang et al, 2017 ), and the P3 amplitudes decreased significantly with increasing cognitive loads (Kok, 2001 ) in the present study. These findings suggest that the electrophysiological findings from such a reference site are still reliable.…”

“…These findings suggest that the electrophysiological findings from such a reference site are still reliable. However, further EEG-fMRI studies aiming to explore the effects of exercise interventions might consider applying the Reference Electrode Standardization Technique (REST) (Yao, 2001 ; Yao et al, 2005 ) as the reference method for ERP data (Yang et al, 2017 ).…”

Electrophysiological Correlates of Change Detection during Delayed Matching Task: A Comparison of Different References

“…Based on such observation, it is reasonable to speculate that the improper use of the LM reference may weaken the strength of posterior electrophysiological signals, thus makes the posterior task related ERP effects disappeared. In fact, not just the scalp distribution of power spectra, the wave amplitude of the scalp potentials, large-scale networks and non-linear features of EEG were also shown to be distorted by the use of LM (Kayser et al, 2007 ; Marzetti et al, 2007 ; Yao et al, 2007 ; Qin et al, 2010 ; Tian and Yao, 2013 ; Chella et al, 2017 ; Lei and Liao, 2017 ; Yang et al, 2017 ). Besides, taking into account the fact that there is no neutral location exists on the human body surface (Nunez et al, 1997 ), the average reference (AR) that relying on human upper scalp electrodes also faces similar theoretical defect (Yao, 2017 ).…”

The neural basis of semantic cognition in Mandarin Chinese: A combined fMRI and TMS study

“…The individual trial onset sequence for semantic judgment task and numerical judgment task were obtained by convolving a canonical hemodynamic response function to form regressors of the design matrix (Gazzaley et al, 2007;Passaro et al, 2013;Robitaille et al, 2010;Yang, Fan, Wang, & Li, 2017). The individual trial onset sequence for semantic judgment task and numerical judgment task were obtained by convolving a canonical hemodynamic response function to form regressors of the design matrix (Gazzaley et al, 2007;Passaro et al, 2013;Robitaille et al, 2010;Yang, Fan, Wang, & Li, 2017).…”

“…At the single subject level, we operated statistical analysis on the basis of the context-based general linear model (GLM) of the experiment. The individual trial onset sequence for semantic judgment task and numerical judgment task were obtained by convolving a canonical hemodynamic response function to form regressors of the design matrix (Gazzaley et al, 2007;Passaro et al, 2013;Robitaille et al, 2010;Yang, Fan, Wang, & Li, 2017).…”