15th International Congress of Phonetic Sciences (ICPhS-15)
To assess pitch-related brain lateralization effects, evoked magnetic fields in response to dichotic rippled noise (RN) were recorded by means of whole-head magneto-encephalography (MEG). Four dichotic stimulus constellations (111- or 133-Hz RN to one ear, white noise to the other) were applied in randomized order. The evoked fields delineated three stages of central-auditory processing. (1) Attention-dependent ear x hemisphere interactions were observed as early as the M50 field (50-80 ms post stimulus onset), presumably reflecting early streaming of auditory information. (2) The relatively late M100 field (136 ms) was significantly lateralized to the left hemisphere, but showed a pitch-related modulation of right- rather than left-hemisphere activity. The observed interaction between periodic and aperiodic signal components suggests this time window to reflect pitch-synchronous spectral evaluation. (3) A time window centered at 192 ms showed a main effect of RN pitch, presumably due to sensory memory operations.
Bibliographic reference. Hertrich, Ingo / Mathiak, Klaus / Lutzenberger, Werner / Ackermann, Hermann (2003): "Time course and lateralization of evoked magnetic fields during complex pitch processing", In ICPhS-15, 1715-1718.