[Information processing in the human brain revealed by eyeblink].

People spontaneously generate an eyeblink every few seconds. It is generally accepted that eyeblinks are necessary for ocular lubrication, but spontaneous eyeblinks actually occur several times more frequently than necessary for lubrication. Thus, the functional role of most spontaneous eyeblinks has remained unclear. We found that peoples blinked in synchrony while viewing the same video stories. This blink synchronization specifically occured at the implicit breakpoints of the video stories. Moreover, in face-to-face communication, the listeners blinked with a delay of 0.25-0.5 s after the speaker blinked at the end and during pauses in speech. In contrast, the individuals with autism spectrum disorders, which are characterized by impaired social communication, did not show any eyeblink synchronization with the speaker. These facts demonstrate that spontaneous eyeblink is involved in the contextual segmentation of information, and that eyeblinks have a social function to share the contextual segmentation with others. Futhermore, our neuroimaging study revealed that, while viewing videos, cortical activity momentarily decreases in the dorsal attention network after blink onset but increases in the default-mode network. These results suggest that the spontaneous eyeblink is involved in the disengagement of attention at an implicit contextual breakpoint by controlling the balance between the two competing networks.