Blink-related momentary activation of the default mode network while viewing videos

Abstract

It remains unknown why we generate spontaneous eyeblinks every few seconds, more often than necessary for ocular lubrication. Because eyeblinks tend to occur at implicit breakpoints while viewing videos, we hypothesized that eyeblinks are actively involved in the release of attention. We show that while viewing videos, cortical activity momentarily decreases in the dorsal attention network after blink onset but increases in the default-mode network implicated in internal processing. In contrast, physical blackouts of the video do not elicit such reciprocal changes in brain networks. The results suggest that eyeblinks are actively involved in the process of attentional disengagement during a cognitive behavior by momentarily activating the default-mode network while deactivating the dorsal attention network.functional MRI | natural vision W e spontaneously generate an eyeblink every few seconds-15-20 per minute, on average. These spontaneous eyeblinks are believed to occur to lubricate the cornea, but the rate is several times more than required for ocular lubrication (1, 2). Therefore, it remains an open question why eyeblinks are generated so frequently at the cost of blocking visual input for a period amounting to 10% of our waking hours (3).Spontaneous eyeblinks tend to occur at breakpoints of attention, such as the end of a sentence while reading (4), a pause by the speaker while listening to a speech (5), and implicit breakpoints while viewing videos (3). That eyeblinks occur not only at explicit but also at implicit breakpoints raises the possibility that spontaneous eyeblinks play an active role in the release of attention from external stimuli while attentively engaging in a cognitive task. Clinical neurological studies support this possibility. People who had a difficulty of voluntary eye movements often generate eyeblinks to terminate the spasms of visual fixations (6-8).Assuming the role of the eyeblink in disengaging attention, each spontaneous eyeblink should be associated with inhibition of the dorsal attentional network that mediates the allocation of attention (9), and with an activation of the default-mode network (DMN), which is known to counteract the dorsal attention network (10) and is implicated in introspection (11, 12). We hypothesized that spontaneous eyeblinks control the disengagement of attention by momentarily deactivating the dorsal attention network while activating the DMN.To test this hypothesis, we used fMRI to examine the cortical activity of 10 healthy participants (mean age: 21.7 y) in relation to the onset of each spontaneous eyeblink while the participants attentively viewed video clips from "Mr. Bean," a British television comedy. The story was chosen because our previous behavioral study demonstrated that the timing of spontaneous eyeblinks was synchronized across participants at the implicit breakpoints of the same video (3). ResultsThe participants spontaneously generated an average of 17.4 eyeblinks per minute (ranging from 3.1-51.0) while viewing the videos. Event-rel...

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