Alpha-band oscillation during speech recognition under different sensory conditions

The recognition mechanism of alpha-band oscillation for background EEG was analyzed during speech recognition under the auditory-only (A), audio-visual (AV) and visual-only (V) conditions. EEG signals for 20 university volunteers were measured at the SNRs of 0, -4, -8, -12 and -16 dB under the A, AV and V conditions. It was indicated that the task-relevant brain areas exhibited ERS under the different three sensory conditions. Brain region of A condition was distributed in the regions of frontal, central, and parietal, whereas those of AV and V conditions were concentrated in the parietal areas. Larger alpha-band power (ERS) of A condition was observed than those of AV and V conditions. The background brightness, objects recognition, relevant-task, and lip movement might contribute to the ERS. It was revealed that alpha-band oscillation can reflect the ability to process the background information for the human brain.