Keceli Sumru, Okamoto Hidehiko, Kakigi Ryusuke
Department of Integrative Physiology, National Institute for Physiological Sciences, Nishigoh-naka 38, Myodaiji, Okazaki, Aichi, 444-8585, Japan,
Brain Topogr. 2015 May;28(3):459-70. doi: 10.1007/s10548-013-0300-3. Epub 2013 Jun 22.
Temporal regularity provides an important cue for the identification of natural sounds. Here, we measured auditory evoked cortical magnetic fields to investigate the neural processing of temporal regularity that cannot be tonotopically represented in the auditory periphery. Auditory steady state responses (ASSR) and sustained fields (SF) elicited by 40 Hz amplitude modulated periodic and non-periodic noises were analyzed. Periodic noises of 40-, 20-, and 5-Hz were prepared in the form of repeating frozen noises where the same noise segment appears at either each period (40 Hz), every second period (20 Hz), or every eighth period (5 Hz) of amplitude modulation. Compared to non-periodic white noises, periodic noises with repetition rates of 5-, 20-, and 40-Hz caused significantly increased SF amplitudes in both hemispheres. ASSR amplitudes were significantly enhanced for 20- and 40-Hz periodic noises in the right hemisphere while no enhancement was observed for periodic noises in the left hemisphere. The observed variation of the regularity effect between evoked response components and hemispheres may reflect the differences in the temporal integration window lengths adopted between ASSR and SF generators and also between the right and left auditory pathways.
时间规律性为自然声音的识别提供了重要线索。在此，我们测量了听觉诱发的皮层磁场，以研究在听觉外周无法按音频拓扑方式表征的时间规律性的神经处理过程。分析了由40赫兹调幅的周期性和非周期性噪声诱发的听觉稳态反应（ASSR）和持续场（SF）。40赫兹、20赫兹和5赫兹的周期性噪声以重复的冻结噪声形式制备，其中相同的噪声片段出现在调幅的每个周期（40赫兹）、每隔一个周期（20赫兹）或每隔八个周期（5赫兹）。与非周期性白噪声相比，重复率为5赫兹、20赫兹和40赫兹的周期性噪声在两个半球均导致SF振幅显著增加。右半球中20赫兹和40赫兹周期性噪声的ASSR振幅显著增强，而左半球的周期性噪声未观察到增强。诱发反应成分和半球之间观察到的规律性效应变化可能反映了ASSR和SF发生器之间以及左右听觉通路之间采用的时间整合窗口长度的差异。
