抄録
Neuromagnetic fields evoked by the auditory stimuli of pure tones and speech sounds were measured, and equivalent current dipoles were calculated based on a least squares method. In the N1m component of the magnetic responses which occurred at about 100ms after the stimulus onset, the location of the current dipole elicited by high frequency tone was deeper and more anterior than that of the dipole elicited by low frquency tone in right and left hemispheres. This result indicates a ‘tonotopic organization’ in the human auditory cortex. In the left hemisphere, the location of the current dipole elicited by the speech sound of a vowel/a/was deeper and more anterior than that of the dipole elicited by a consonant-vowel/ka/. It is suggested that the magnetic responses reflect the activity of the neurons responding to acoustic, and also possibly phonetic, characteristics of the auditory stimuli. These differences of the dipole locations for different stimuli were analyzed by computer simulations evaluating the error range of the dipole location.
