Amplitude of fNIRS Resting-State Global Signal Is Related to EEG Vigilance Measures: A Simultaneous fNIRS and EEG Study

Abstract

Recently, functional near-infrared spectroscopy (fNIRS) has been utilized to image the hemodynamic activities and connectivity in the human brain. With the advantage of economic efficiency, portability, and fewer physical constraints, fNIRS enables studying of the human brain at versatile environment and various body positions, including at bed side and during exercise, which complements the use of functional magnetic resonance imaging (fMRI). However, like fMRI, fNIRS imaging can be influenced by the presence of a strong global component. Yet, the nature of the global signal in fNIRS has not been established. In this study, we investigated the relationship between fNIRS global signal and electroencephalogram (EEG) vigilance using simultaneous recordings in resting healthy subjects in high-density and whole-head montage. In Experiment 1, data were acquired at supine, sitting, and standing positions. Results found that the factor of body positions significantly affected the amplitude of the resting-state fNIRS global signal, prominently in the frequency range of 0.05–0.1 Hz but not in the very low frequency range of less than 0.05 Hz. As a control, the task-induced fNIRS or EEG responses to auditory stimuli did not differ across body positions. However, EEG vigilance plays a modulatory role in the fNIRS signals in the frequency range of less than 0.05 Hz: resting-state sessions of low EEG vigilance measures are associated with high amplitudes of fNIRS global signals. Moreover, in Experiment 2, we further examined the epoch-to-epoch fluctuations in concurrent fNIRS and EEG data acquired from a separate group of subjects and found a negative temporal correlation between EEG vigilance measures and fNIRS global signal amplitudes. Our study for the first time revealed that vigilance as a neurophysiological factor modulates the resting-state dynamics of fNIRS, which have important implications for understanding and processing the noises in fNIRS signals.

Concurrent fNIRS and EEG for Brain Function Investigation: A Systematic, Methodology-Focused Review

“…Among the eighteen articles reviewed here ( Table 4 ), correlational analyses of concurrent fNIRS–EEG have mainly focused on correlation and coherence analyses. Pearson correlation, partial correlation, and simple linear regression are commonly used measures for assessing the relationship between the event-related potential pattern in EEG and hemodynamic changes in fNIRS [ 101 , 102 , 103 , 104 , 105 , 106 , 107 , 108 , 109 , 110 ]. Several studies assessed the relationship between EEG and fNIRS signal through cross-correlation analysis and canonical correlation analysis (CCA) [ 111 , 112 , 113 , 114 ].…”

Functional near-infrared spectroscopy imaging of the prefrontal cortex during a naturalistic comedy movie

“…However, the signal used in our analysis still contained the global (systemic) signal component; therefore, our results can at least to some extent be explained by the global signal component. The physiological nature of the fNIRS global signal is not fully understood ( Chen Y. et al, 2020 ), while a possible cause of the global signal phenomenon is that near-infrared light, by passing through superficial layers of blood vessels in the skin, changes the signal ( Zhang et al, 2016 ). The global signal might also reflect levels of arousal and vigilance ( Chen Y. et al, 2020 ).…”

“…The physiological nature of the fNIRS global signal is not fully understood ( Chen Y. et al, 2020 ), while a possible cause of the global signal phenomenon is that near-infrared light, by passing through superficial layers of blood vessels in the skin, changes the signal ( Zhang et al, 2016 ). The global signal might also reflect levels of arousal and vigilance ( Chen Y. et al, 2020 ). The global signal might obscure in particular the results of resting-state connectivity analysis ( Obrig et al, 2000 ; White et al, 2009 ; Duan et al, 2018 ; Chen Y. et al, 2020 ).…”

“…The global signal might also reflect levels of arousal and vigilance ( Chen Y. et al, 2020 ). The global signal might obscure in particular the results of resting-state connectivity analysis ( Obrig et al, 2000 ; White et al, 2009 ; Duan et al, 2018 ; Chen Y. et al, 2020 ). This is because in this analysis, the time-courses of different regions within the same person are correlated, so the presence of a global signal might artificially boost correlation.…”

Internal Consistency of Sway Measures via Embedded Head-Mounted Accelerometers: Implications for Neuromotor Investigations

“…These accelerometers are ideally situated for the development of a multimodal (i.e., the simultaneous use of both neuroimaging and accelerometry) study protocol, which would enable investigations into the relationship between modalities. While functional near-infrared spectroscopy (fNIRS) and electroencephalography (EEG) have been combined to evaluate gait and standing balance (for a review, see [ 27 , 28 , 29 ]), the relationship between brain functionality and balance has not been examined using multiple neuroimaging modalities. This new multimodal experimental design could have huge implications for clinical populations suffering neurological conditions affecting balance.…”