Phonetic and pure-tones-pair induced changes in the stable EEG power spectrum

The changes in power spectrum of stable EEG from subjects who have listened to pure-tones-pair and a phonetic sound are found to be different and specific. A pure-tones-pair induction leads to the increase in the amplitude of the power spectrum in temporal region whereas the phonetic induction leads to the increase in the amplitude of the power spectrum in the frontal and the occipital regions. This paper presents the results of the experiments that led to the above observations. The pure-tones-pair used in the experiment was a pair of 400 and 406 Hz frequencies listened through individual ears simultaneously and the phonetic sound was "Om". The auditory stimuli were given for twenty minutes everyday for twenty successive days. The power spectra of the pre- and post-averaged stable EEG measurements were obtained using a PC-AT based FFT analyser. These spectra were optionally corrected for removing the interference from eye movements and were compared. The temporal region enhancement due to the pure-tones-pair correlates well with the earlier findings that excitation by the difference beat frequency of 6 Hz helps in retrieving from memory as well as in enhancing the memorising function through the hippocampus region. Difference in the region of significant enhancement (fronto-occipital as against temporal) with the phonetic sound excitation (in this case "Om") may be of special interest to EEG researchers concerned with enhancement of higher brain functions.