The relationship between the amplitude and phase of alpha waves and the task existence in a single stimulus paradigm

In this paper, we studied the relationship between the amplitude and phase of an alpha wave and task existence as a first step to investigating changes in the background wave after sensory stimulus. We examined the effect of a single sensory stimulus, visual or auditory, on the amplitude and the phase of alpha waves using a complex demodulation method. This experiment was performed with four conditions which were combinations of two kinds of tasks, task and no task, and two kinds of sensory stimulus, visual and auditory A flash pulse was used as the visual stimulus and a tone burst sound as an auditory stimulus in the eyes-closed condition. As a result, the amplitude in the task condition was larger than in the no task condition. Alpha blocking and rebound after the stimulus appears, regardless of the kind of sensory stimulus, whether a visual or an auditory stimulus. However, that on the task condition in the visual stimulus is not so prominent. We saw two peaks in the rebound section. One appears just after the alpha blocking and the other appears at around 2000 ms. The degree of alpha blocking on the task is larger than that on no task. However, the degree of rebound on the task is nearly the same as with that of no task. As for the phase change, it varied in the section from after the stimulus onset to 2500 ms after the stimulus. This phenomenon is more prominent in the visual stimulus compared with the auditory stimulus. The phase change returned to the level it was at before the stimulus, at around 3000 ms.