Resting-State Fluctuations of EEG Sensorimotor Rhythm Reflect BOLD Activities in the Pericentral Areas: A Simultaneous EEG-fMRI Study.

Hiroki Ebata,Kenji Kato,Takashi Hanakawa,Nobuaki Mizuguchi,Shuka Shibusawa,Junichi Ushiba,Shohei Tsuchimoto,Meigen Liu

doi:10.3389/fnhum.2017.00356

Abstract

Blockade of the scalp electroencephalographic (EEG) sensorimotor rhythm (SMR) is a well-known phenomenon following attempted or executed motor functions. Such a frequency-specific power attenuation of the SMR occurs in the alpha and beta frequency bands and is spatially registered at primary somatosensory and motor cortices. Here, we hypothesized that resting-state fluctuations of the SMR in the alpha and beta frequency bands also covary with resting-state sensorimotor cortical activity, without involving task-related neural dynamics. The present study employed functional magnetic resonance imaging (fMRI) to investigate the neural regions whose activities were correlated with the simultaneously recorded SMR power fluctuations. The SMR power fluctuations were convolved with a canonical hemodynamic response function and correlated with blood-oxygen-level dependent (BOLD) signals obtained from the entire brain. Our findings show that the alpha and beta power components of the SMR correlate with activities of the pericentral area. Furthermore, brain regions with correlations between BOLD signals and the alpha-band SMR fluctuations were located posterior to those with correlations between BOLD signals and the beta-band SMR. These results are consistent with those of event-related studies of SMR modulation induced by sensory input or motor output. Our findings may help to understand the role of the sensorimotor cortex activity in contributing to the amplitude modulation of SMR during the resting state. This knowledge may be applied to the diagnosis of pathological conditions in the pericentral areas or the refinement of brain–computer interfaces using SMR in the future.

Highlights

Since Berger’s first electroencephalogram (EEG) recordings from the human scalp in the late 1920s, a number of studies have led to new insights into the function and mechanisms of intrinsic oscillations underlying brain activities (Niedermeyer and da Silva, 2005)
The sensorimotor rhythm (SMR) signals are recorded from the C3 channel that is located closest to the hand area in sensorimotor area and its amplitude is known to be reduced by desynchronized neural activities in association with motor-related events, such as kinesthetic motor imagery or actual muscle contraction, suggesting a possible electrophysiological sign of sensorimotor excitability (Pfurtscheller et al, 2006)
Based upon previous knowledge suggesting an association between spontaneous SMR fluctuation during the resting state and activity of the pericentral brain regions, we addressed the following hypotheses: (1) the spontaneous SMR power modulations were correlated with a surrogate marker of brain activity that covaries with resting-state sensorimotor cortical activity as measured by blood-oxygen-level dependent (BOLD)-functional magnetic resonance imaging (fMRI) in the pericentral area, and (2) the area correlated with alpha-band SMR was located posterior to the area correlated with beta-band SMR

Summary

INTRODUCTION

Since Berger’s first electroencephalogram (EEG) recordings from the human scalp in the late 1920s, a number of studies have led to new insights into the function and mechanisms of intrinsic oscillations underlying brain activities (Niedermeyer and da Silva, 2005). In the postmovement period, the amplitude of the beta-band consistently returns to and exceeds pre-movement levels via synchronization (Pfurtscheller et al, 1996a; Bauer et al, 2006; Jurkiewicz et al, 2006; Parkes et al, 2006) These studies suggest that the beta component of the SMR is more motor-related. Based upon previous knowledge suggesting an association between spontaneous SMR fluctuation during the resting state and activity of the pericentral brain regions, we addressed the following hypotheses: (1) the spontaneous SMR power modulations were correlated with a surrogate marker of brain activity that covaries with resting-state sensorimotor cortical activity as measured by BOLD-fMRI in the pericentral area, and (2) the area correlated with alpha-band SMR was located posterior to the area correlated with beta-band SMR. We employed EEG-fMRI simultaneous recording to identify the relationship between SMR modulations and whole-brain activity during the resting state

MATERIALS AND METHODS

EEG Results

DISCUSSION

Study Limitation