Okamoto Hidehiko, Kakigi Ryusuke
Department of Integrative Physiology, National Institute for Physiological SciencesOkazaki, Japan; Department of Physiological Sciences, Graduate University for Advanced StudiesHayama, Japan.
Front Hum Neurosci. 2017 Feb 6;11:36. doi: 10.3389/fnhum.2017.00036. eCollection 2017.
In our daily life, we are successively exposed to frequency-modulated (FM) sounds that play an important role in speech and species-specific communication. Previous studies demonstrated that repetitive exposure to identical pure tones resulted in decreased neural activity. However, the effects of repetitively presented FM sounds on neural activity in the human auditory cortex remain unclear. In the present study, we used magnetoencephalography to investigate auditory evoked N1m responses elicited by four successive temporally repeated and superimposed FM sweeps in three sequences: (1) four FM sweeps were identical, (2) four FM sweeps had the same FM direction and rate, but different carrier frequencies, (3) four FM sweeps differed with respect to the FM rate and/or direction and their carrier frequencies. In contrast to our expectations, the results obtained demonstrated that N1m responses were maximal when the four FM sweeps were identical and minimal when they were distinct. These results suggest that the neural processing of repetitive FM sweeps in the human auditory cortex may differ from that of repetitive pure tones.
在我们的日常生活中，我们会相继接触到调频（FM）声音，这些声音在言语和物种特异性交流中发挥着重要作用。先前的研究表明，反复接触相同的纯音会导致神经活动减少。然而，反复呈现的调频声音对人类听觉皮层神经活动的影响仍不清楚。在本研究中，我们使用脑磁图来研究在三个序列中由四个连续的时间重复和叠加的调频扫描诱发的听觉诱发N1m反应：（1）四个调频扫描相同，（2）四个调频扫描具有相同的调频方向和速率，但载波频率不同，（3）四个调频扫描在调频速率和/或方向及其载波频率方面有所不同。与我们的预期相反，所得结果表明，当四个调频扫描相同时，N1m反应最大，而当它们不同时，N1m反应最小。这些结果表明，人类听觉皮层中重复调频扫描的神经处理可能与重复纯音的神经处理不同。
