Turning the Stimulus On and Off Changes the Direction of α Traveling Waves.

Traveling waves have been studied to characterize the complex spatiotemporal dynamics of the brain. Several studies have suggested that the propagation direction of α traveling waves can be task dependent. For example, a recent electroencephalography (EEG) study from our group found that forward waves (i.e., occipital to frontal, FW waves) were observed during visual processing, whereas backward waves (i.e., frontal to occipital, BW waves) mostly occurred in the absence of sensory input. These EEG recordings, however, were obtained from different experimental sessions and different groups of subjects. To further examine how the waves' direction changes between task conditions, 13 human participants were tested on a target detection task while EEG signals were recorded simultaneously. We alternated visual stimulation (5-s display of visual luminance sequences) and resting state (5 s of black screen) within each single trial, allowing us to monitor the moment-to-moment progression of traveling waves. As expected, the direction of α waves was closely linked with task conditions. First, FW waves from occipital to frontal regions, absent during rest, emerged as a result of visual processing, while BW waves in the opposite direction dominated in the absence of visual inputs, and were reduced (but not eliminated) by external visual inputs. Second, during visual stimulation (but not rest), both waves coexisted on average, but were negatively correlated. In summary, we conclude that the functional role of α traveling waves is closely related with their propagating direction, with stimulus-evoked FW waves supporting visual processing and spontaneous BW waves involved more in top-down control.

Learning Desire Is Predicted by Similar Neural Processing of Naturalistic Educational Materials.

Naturalistic stimuli can elicit highly similar brain activity across viewers. How do naturalistic educational materials engage human brains and evoke learning desire? Here, we presented 15 audiovisual course clips (each lasting ∼120 s) to university students and recorded their neural activity through electroencephalography. Upon finishing all the video viewings, subjects ranked 15 courses in order of learning desire and reported the reasons for high learning desire (i.e., "value" and "interest"). The brain activity during the video viewing was measured as the neural similarity via intersubject correlation (ISC), that is, correlation between each subject's neural responses and those of others. Based on averaged learning desire rankings across subjects, course clips were classified with high versus medium versus low motivational effectiveness. We found that the ISC of high effective course clips was larger than that of low effective ones. The ISC difference (high vs low) was positively associated with subjects' learning desire difference (high vs low). Such an association occurred when viewing time accumulated to ∼80 s. Moreover, ISC was correlated with "interest-based" rather than "value-based" learning desire. These findings advance our understanding of learning motivation via the neural similarity in the context of on-line education and provide potential neurophysiological suggestions for pedagogical practices.