Influence of Visual Stimulus on Amplitude and Phase of Alpha Wave as Measured by Multi-Channel EEG

Tadanori FUKAMI  Kazuhito HAYASHI  Takamasa SHIMADA  Takao AKATSUKA  Yoichi SAITO  

Publication
IEICE TRANSACTIONS on Information and Systems   Vol.E86-D   No.11   pp.2444-2451
Publication Date: 2003/11/01
Online ISSN: 
DOI: 
Print ISSN: 0916-8532
Type of Manuscript: PAPER
Category: Medical Engineering
Keyword: 
complex demodulation method,  amplitude,  phase,  alpha wave,  visual stimulus,  

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Summary: 
The objective of this paper is to study the relationship between a visual stimulus and the amplitude and phase of the alpha wave as a first step to investigating a change in the background wave after a sensory stimulus and an evoked potential. We examined the effect of a single visual stimulus on the amplitude and phase of alpha waves using the complex demodulation method. The visual stimuli were generated by an LED mounted in goggles with the eyes-closed condition. The amplitude of the alpha wave decreased gradually after the stimulus, until it reached a minimum at around 300 ms after the stimulus. The alpha wave continued to increase, showing some rebound, and returning again to the pre-stimulus level. The phase variation after the stimulus tends to be considerably larger than that before the stimulus. Moreover, the average phase returned to the same slope as the pre-stimulus by 2550 ms after the stimulus. The visual stimulus has an effect on the alpha wave until about 2500 ms after the stimulus. The phase variation difference before and after stimulus is significant from 112 ms to 678 ms after the stimulus. This finding suggests there is a partially pararell time course between the change in VEPs plus ERP complex and the alpha wave.