抄録
The author has applied the key-tapping method to detect auditory cerebral dominance in normal subjects since 1965, and it has been revealed that steady-state vowels and human emotional sounds in duration of 50 to 75 milliseconds were dominantly processed in the right hemisphere in non-Japanese people including Westerners and in the left in Japanese.
The laterality of pure tone sounds, which shows the left ear advantage (LEA) in the strictly controlled normal condition in both Japanese and non-Japanese, is changed from LEA to right ear advantage (REA) under the influence of verbal stimulation, such as listening to a speech, vocalization, reading a book, and opening the mouth.
In addition to the above-mentioned conditions, a person who spoke Japanese as his mother tongue until 8 years of age showed a shift of nonverbal sound laterality by the influence of the emotional stimulation or the irritation of the autonomic nervous system such as smelling, sexual ejaculation, breath-holding, unilateral pressure on the cervical artery and thermal stimulation on the left side of the scalp.
The reason why the shift of laterality was found exclusively in Japanese and not in non-Japanese is explained using the assumption that the emotional function is closely related to the verbal hemisphere in Japanese and not in non-Japanese.
By applying successive pure tone sounds from 30 to 110Hz, the characteristics of the laterality of each pure tone was confirmed. The author found that the lower frequency range less than 99Hz, except 40Hz—showed REA. The significance of 40Hz was discussed.
