Investigation for the activation mechanism of deep brain structures caused by high frequency components above the audible range

虽然人们普遍认为，人类不能在20千赫以上的频率范围内感知声音，但这种“不可听”高频成分的存在是否会影响对可听声音的声学感知的问题仍未得到回答。利用对大脑反应的非侵入性生理测量，我们提供了证据，证明在可听范围以上包含高频分量(HFC)的声音显著影响听者的大脑活动。我们使用巴厘岛的加麦兰音乐作为天然声源，将其分为两个分量：22 kHz以下的可听低频分量(LFC)和22 kHz以上的HFC。当受试者暴露在LFC和HFC的不同组合的声音中时，测量脑电活动和局部脑血流量(RCBF)作为神经元活动的标志，当HFC单独呈现时，没有一个受试者将其识别为声音。Neverthele…当受试者暴露于同时含有HFC和LFC的声音时，从枕区记录的自发脑电(α-EEG)的α频率范围的功率谱比暴露于去除HFC的相同声音(即单独的LFC)时更多，具有统计学意义。相反，与基线相比，当HFC或LFC单独呈现时，α-EEG没有明显的增强。PET测量显示，当HFC和LFC同时出现时，与其他相同的声音相比，脑干和左侧丘脑的rCBF显著增加，但HFC的频率高于22 kHz。同步脑电测量显示，枕叶α-EEG的功率与左侧丘脑的rCBF显著相关。心理评估表明，受试者觉得含有HFC的声音比没有HFC的相同声音更愉快。这些结果表明，对于包含特定类型高频的复杂声音，存在着一种以前无法识别的反应，这些声音的频率高于可听范围。我们把这种现象称为“高超声速效应”。较少

Although it is generally accepted that humans cannot perceive sounds in the frequency range above 20 kHz, the question of whether the existence of such "non-audible" high-frequency components may affect the acoustic perception of audible sounds remains unanswerd. Using Noninvasive physiological measurements of brain responses, we provide evidence that sounds containing high-frequency components (HFC) above the audible range is significantly affect the brain activity of listeners. We used the gamelan music of Bali, which is extremely rich in HFC with a nonstationary structure, as a natural sound source, dividing it into two components: an audible low-frequency component (LFC) below 22 kHz and a HFC above 22 kHz. Brain electrical activity and regional cerebral blood flow (rCBF) were measured as markers of neuronal activity while subjects were exposed to sounds with various combinations of LFC and HFC.None of the subjects recognized the HFC as sound when it was presented alone. Neverthele … More ss, the power spectra of the alpha frequency range of the spontaneous electroencephalogram (alpha-EEG) recorded from the occipital region increased with statistical significance when the subjects were exposed to sound which contained both HFC and LFC, compared with an otherwise identical sound from which the HFC was removed (I.e., LFC alone). In contrast, compared with the baseline, no enhancement of alpha-EEG was evident when either HFC or LFC was presented separately. PET measurements revealed that, when HFC and LFC were presented together, the rCBF in the brainstem and the left thalamus increased significantly compared with an otherwise identical sound except Jacking the HFC above 22 kHz. Simultaneous EEG measurements showed that the power of occipital alpha-EEGs correlated significantly with the rCBF in the left thalamus. Psychological evaluation indicated that the subjects felt the sound containing HFC to be more pleasant than the same sound lacking HFC.These results suggest the existence of a previously unrecognized response to complex sound containing particular types of high frequencies above the audible range. We term this phenomenon the "hypersonic effect". Less