Characteristics of travelling waves under various conditions

In this mapping study, the goal was to investigate in 10 subjects the phenomenon of the travelling waves (TW), especially of alpha activity, under conditions of (1) rest, (2) calculations, (3) emotional experience and (4) pain. The TW during wakefulness usually arose from the areas with the highest amplitude of alpha, called major peaks, for both positive (pos.) and negative (neg.) polarities. These areas were Pz (pos. and neg.) at rest, O2 (pos.) and Pz (neg.) during calculation, O1 (pos.) and O2 (neg.) during emotion and T6 (pos.) and O1 (neg.) during pain. When differences were determined between the latter 3 conditions and the resting state, a focal event-related desynchronization (ERD) became evident on T5 during math, on Pz during emotion and on both CP areas during pain. Surrounding the areas of ERD were areas of event-related synchronization (ERS). The TW were related to phase differences between the different electrode locations, seen more frequently with the pos. polarity, and more often with emotion or calculation. The direction of the TW was most often toward the midline during rest, from the right to midline (calculation), from the left to midline (emotion) and from the midline to the left (pain). Changes on one side of the head were often associated with opposite types of changes on the other side. Sleep spindles were also analyzed showing the major peaks on Fz and F4 with pos. polarities often seen anteriorly and neg. polarities posteriorly. TW were also seen with spindles, more often with the positive polarity. The direction was usually from the midline for the positive polarity and toward the midline for the neg. phase. The phenomenon of the TW is discussed, especially its possible neurophysiological significance as a means of transmitting information throughout the brain.