Magnetoencephalographic activities related to the magnitude of the interaural cross-correlation function (IACC) of sound fields
Yoshiharu Soeta, Seiji Nakagawa and Mitsuo Tonoike
Magnetoencephalographic (MEG) responses to the magnitude of the interaural cross-correlation function (IACC) of a sound field were investigated. The source signal was the word "piano", which had a 0.35-s duration. In MEG measurements, combinations of a reference stimulus (IACC = 1.0) and test stimuli (IACC = 0.27, 0.61, and 0.90) were presented 50 times alternately at a constant 1.5-s interstimulus interval. The MEG responses evoked by each stimulus in the pair were integrated and recorded with a 122-channel whole-head neuromagnetometer and analyzed using an autocorrelation function (ACF) and a cross-correlation function (CCF). The results showed that the effective duration of ACF, te, and the maximum value of CCF, |f(t)|max, of MEG between 8-13 Hz become larger as the IACC decrease. Although subjective preference tests for the IACC of speech sound fields have not been conducted in the present study, the previous studies of subjective preference for sound fields have showed that lower IACC is preferred. Therefore the results indicate that the brain repeats a similar temporal rhythm over a wider area under preferred sound fields.
Keywords: autocorrelation function (ACF), cross-correlation function (CCF), magnetoencephalography (MEG), magnitude of interaural cross-correlation function (IACC)