Oohashi Tsutomu, Kawai Norie, Nishina Emi, Honda Manabu, Yagi Reiko, Nakamura Satoshi, Morimoto Masako, Maekawa Tadao, Yonekura Yoshiharu, Shibasaki Hiroshi
Department of Research and Development, Foundation for Advancement of International Science, Tokyo 164-0003, Japan.
Brain Res. 2006 Feb 16;1073-1074:339-47. doi: 10.1016/j.brainres.2005.12.096. Epub 2006 Feb 2.
Although human beings cannot perceive elastic vibrations in the frequency range above 20 kHz, nonstationary sounds containing a wealth of inaudible high-frequency components (HFC) above the human audible range activate deep-lying brain structures, including the brainstem and thalamus and evoke various physiological, psychological, and behavioral responses. In the previous reports, we have called these phenomena collectively "the hypersonic effect." It remains unclear, however, if vibratory stimuli above the audible range are transduced and perceived solely via the conventional air-conducting auditory system or if other mechanisms also contribute to mediate transduction and perception. In the present study, we have examined the emergence of the hypersonic effect when inaudible HFC and audible low-frequency components (LFC) were presented selectively to the ears, the entrance of an air-conducting auditory system, or to the body surface including the head which might contain some unknown vibratory sensing mechanisms. We used two independent measurements based on differing principles; one physiological (alpha 2 frequency of spontaneous electroencephalogram [alpha-EEG]) and the other behavioral (the comfortable listening level [CLL]). Only when the listener's entire body surface was exposed to HFC, but not when HFC was presented exclusively to the air-conducting auditory system, did both the alpha-EEG and the CLL significantly increase compared to the presentation of LFC alone, that is to say, there was an evident emergence of the hypersonic effect. The present findings suggest that the conventional air-conducting auditory system alone does not bring about the hypersonic effect. We may need to consider the possible involvement of a biological system distinct from the conventional air-conducting auditory nervous system in sensing and transducing high-frequency elastic vibration above the human audible range.
尽管人类无法感知频率高于20 kHz的弹性振动，但包含大量人类可听范围以上听不见的高频成分（HFC）的非平稳声音会激活深层脑结构，包括脑干和丘脑，并引发各种生理、心理和行为反应。在之前的报告中，我们将这些现象统称为“超声波效应”。然而，目前尚不清楚可听范围以上的振动刺激是否仅通过传统的气导听觉系统进行传导和感知，或者是否有其他机制也有助于介导传导和感知。在本研究中，我们研究了在听不见的HFC和听得见的低频成分（LFC）分别选择性地作用于耳朵（气导听觉系统的入口）或作用于可能包含一些未知振动传感机制的包括头部在内的身体表面时，超声波效应的出现情况。我们基于不同原理进行了两项独立测量；一项是生理测量（自发脑电图的α2频率[α-EEG]），另一项是行为测量（舒适聆听水平[CLL]）。只有当聆听者的整个身体表面暴露于HFC时，而不是仅将HFC作用于气导听觉系统时，与单独呈现LFC相比，α-EEG和CLL才会显著增加，也就是说，出现了明显的超声波效应。目前的研究结果表明，仅传统的气导听觉系统不会产生超声波效应。我们可能需要考虑在感知和传导人类可听范围以上的高频弹性振动方面，可能存在一个与传统气导听觉神经系统不同的生物系统。
