Spontaneous Blinks Activate the Precuneus: Characterizing Blink-Related Oscillations Using Magnetoencephalography

Abstract

Spontaneous blinking occurs 15–20 times per minute. Although blinking has often been associated with its physiological role of corneal lubrication, there is now increasing behavioral evidence suggesting that blinks are also modulated by cognitive processes such as attention and information processing. Recent low-density electroencephalography (EEG) studies have reported so-called blink-related oscillations (BROs) associated with spontaneous blinking at rest. Delta-band (0.5–4 Hz) BROs are thought to originate from the precuneus region involved in environmental monitoring and awareness, with potential clinical utility in evaluation of disorders of consciousness. However, the neural mechanisms of BROs have not been elucidated. Using magnetoencephalography (MEG), we characterized delta-band BROs in 36 healthy individuals while controlling for background brain activity. Results showed that, compared to pre-blink baseline, delta-band BROs resulted in increased global field power (p < 0.001) and time-frequency spectral power (p < 0.05) at the sensor level, peaking at ~250 ms post-blink maximum. Source localization showed that spontaneous blinks activated the bilateral precuneus (p < 0.05 FWE), and source activity within the precuneus was also consistent with sensor-space results. Crucially, these effects were only observed in the blink condition and were absent in the control condition, demonstrating that results were due to spontaneous blinks rather than as part of the inherent brain activity. The current study represents the first MEG examination of BROs. Our findings suggest that spontaneous blinks activate the precuneus regions consistent with environmental monitoring and awareness, and provide important neuroimaging support for the cognitive role of spontaneous blinks.

Cognitive loading via mental arithmetic modulates effects of blink‐related oscillations on precuneus and ventral attention network regions

“…Crucially, previous MEG findings from our group further confirmed that delta BROs activated the bilateral precuneus regions known to be involved in environmental monitoring and self-awareness processes (Cavanna & Trimble, 2006;Liu et al, 2017). The precuneus is a critical hub within the default mode network (DMN), a network of brain regions exhibiting increased activity under rest-like conditions Hagmann et al, 2008).…”

“…BROs are believed to represent the cognitive processes associated with blinking, distinct from the well-known ocular and motor effects. A recent study in our group also demonstrated these temporal and spectral characteristics using magnetoencephalography (MEG), further validating the existence of BRO effects across different modalities (Liu, Ghosh Hajra, Cheung, Song, & D'Arcy, 2017). Specifically, the delta-band EEG amplitude and spectral power both exhibit increases following blink events, peaking at~250-300 ms post-blink (Bonfiglio et al, 2009(Bonfiglio et al, , 2013(Bonfiglio et al, , 2014.…”

“…Subsequent blink detection and evaluation followed an automated template matching procedure in accordance with previously published methods (Bonfiglio et al, 2013;Liu et al, 2017). Data were first visually inspected, then notch-filtered to remove power line noise, associated harmonics, and signal due to head position indicator coils.…”

“…To enable quantitative assessment of blink behavioral characteristics across individuals, features were extracted from the vEOG recording that corresponded to different aspects of blink morphology ( Figure 1a) (Bonfiglio et al, 2014;Liu et al, 2017). Features were derived at the individual level after averaging together all identified blink events, and compared at the group level using paired t-test to examine within-subject behavioral differences between the MA and PF tasks.…”

“…Given the interruptions in visual input produced by spontaneous blinking, the observed increase in precuneal activity-above the tonic levels-following blink events is thought to represent additional environmental monitoring processes undertaken when the eyes close and reopen with each new blink (Bonfiglio et al, 2013(Bonfiglio et al, , 2014Liu et al, 2017). The fact that these processes occur as part of blinking at rest also confers possible evolutionary advantages, because the ongoing scanning of the environment for potential threat detection would likely have been necessary to compensate for the momentary loss of visual input due to blinking.…”