RELATIVE ALPHA-DESYNCHRONIZATION AND ALPHA-SYNCHRONIZATION DURING SPEECH-PERCEPTION

Brain processes elicited by speech were studied in IO right-handed sub jects by means of examining the desynchronization and synchronization of the 8-10 Hz and 10-12 Hz EEG alpha frequency bands. The subjects li stened to an auditorily presented 5 min text passage. The text was pre sented both forward and backward. Listening to the text forward elicit ed alpha desynchronization in both of the frequency bands studied, whe reas listening to the same text presented backward elicited synchroniz ation in the 10-12 Hz frequency band only. Listening to the text forwa rd elicited greater desynchronization than listening to the text backw ard. In the 10-12 Hz frequency band, listening to the text forward eli cited desynchronization whereas listening to the same text backward el icited synchronization. This dissociation was not observed in the 8-10 Hz frequency band. The results suggest that the lower and upper alpha bands differ such that the 10-12 Hz frequency band exhibits reactivit y to the presence of linguistic content while the 8-10 Hz band shows a n unspecific response.