When Brain Waves Go Traveling

In July last year I asked, Could Traveling Waves Upset Cognitive Neuroscience? This was a post about a paper from David Alexander et al. arguing that neuroscience was overlooking the importance of how neural activity moves or travels through the brain. Now Alexander et al. are back with a new PLoS ONE paper in which they describe traveling waves in human brain activity, as measured with magnetoencephalography (MEG). The authors scanned 20 volunteers during a visual and auditory task. Alexander et al. focussed on "the class of waves which are characterized by a linear trajectory in the Cartesian coordinates of the sensor space." Here's a visualization. On the left we see a classical standing wave, on the right is a traveling wave. On this image, the horizontal axis is time and the vertical axis is space - each row represents one of the MEG scanner's 151 sensors, arranged around the ...