Destabilization of alpha wave during and after listening to unpleasant and pleasant acoustic stimuli

Spatiotemporal responses of brain alpha wave to unpleasant and pleasant acoustic stimuli are investigated in terms of the amplitude and phase of the alpha wave. The amplitude of the alpha wave is significantly reduced not only during listening to unpleasant acoustic stimuli but also after listening to the stimuli such as teeth gnashing and a single frequency tone with a frequency of 5 K Hz. Amplitude fluctuation is monotonically increased from the onset to 100 s after the offset of listening to the unpleasant stimuli. Such amplitude instability is also observed during listening to pleasant acoustic stimuli such as classical music and babble of a stream, but is not statistically significant after listening to the stimuli. Temporal phase change rate of the alpha wave is significantly increased during and after listening to the unpleasant acoustic stimuli, whereas it is not significantly changed for the pleasant music. The destabilization effect of the unpleasant stimuli on the alpha wave seems to remain for a longer period than that of the pleasant stimuli.