OPM-MEG reveals dynamics of beta bursts underlying attentional processes in sensory cortex

Abstract

Abstract Human brain electrophysiology is dominated by rhythmic activity—neural oscillations—which play an important role in coordinating brain function. In the somatosensory cortices, the dominant oscillations occur in the beta (13–30 Hz) band and are thought to mediate top-down inhibition of primary cortices. The non-invasive measurement of such oscillations has traditionally been made possible using either electroencephalography (EEG) or magnetoencephalography (MEG), yet both modalities have significant limitations. Here, we use a new MEG technology—based on optically pumped magnetometers (OPM-MEG)—to measure attentional modulation of beta oscillations in the somatosensory cortex. Using piezo-electric crystal stimulators, we present ‘braille-like’ patterns to the left and right index fingers; participants are asked to respond to pre-specified target patterns presented to an attended hand, whilst ignoring patterns presented to their non-attended hand. In agreement with previous findings, we measure significantly decreased beta amplitude during attended stimuli relative to non-attended stimuli, with the most pronounced effect immediately following an attentional cue. Moreover, we extend our analyses to demonstrate that attention has a similar effect on the occurrence of pan-spectral bursts (which underlie the beta rhythm). Specifically, we measure significant changes in the probability of burst occurrence in primary somatosensory cortices in a time window related to attentional shifts. In sum, our results provide evidence that attentional modulation of beta oscillations is driven by changes in pan-spectral burst occurrence and add weight to the argument that OPM-MEG is becoming the technique of choice for non-invasive electrophysiological measurements.