Research Institute for Science and Technology, Tokyo Denki University, Adachi-ku, Tokyo 120-855, Japan.
Hear Res. 2013 Feb;296:25-35. doi: 10.1016/j.heares.2012.11.002. Epub 2012 Nov 19.
The auditory steady-state response (ASSR) is a weak potential or magnetic response elicited by periodic acoustic stimuli with a maximum response at about a 40-Hz periodicity. In most previous studies using amplitude-modulated (AM) tones of stimulus sound, long lasting tones of more than 10 s in length were used. However, characteristics of the ASSR elicited by short AM tones have remained unclear. In this study, we examined magnetoencephalographic (MEG) ASSR using a sequence of sinusoidal AM tones of 0.78 s in length with various tone frequencies of 440-990 Hz in about one octave variation. It was found that the amplitude of the ASSR was invariant with tone frequencies when the level of sound pressure was adjusted along an equal-loudness curve. The amplitude also did not depend on the existence of preceding tone or difference in frequency of the preceding tone. When the sound level of AM tones was changed with tone frequencies in the same range of 440-990 Hz, the amplitude of ASSR varied in a proportional manner to the sound level. These characteristics are favorable for the use of ASSR in studying temporal processing of auditory information in the auditory cortex. The lack of adaptation in the ASSR elicited by a sequence of short tones may be ascribed to the neural activity of widely accepted generator of magnetic ASSR in the primary auditory cortex.
听觉稳态响应 (ASSR) 是一种由周期性声刺激引起的微弱电位或磁场反应，其最大响应频率约为 40 Hz。在以前使用调幅 (AM) 音调作为刺激音的大多数研究中，使用了持续时间超过 10 秒的长调。然而，由短 AM 音调引起的 ASSR 的特征仍不清楚。在这项研究中，我们使用持续时间为 0.78 秒、频率范围为 440-990 Hz 的正弦 AM 音调序列，检查了脑磁图 (MEG) ASSR。结果发现，当声压级沿着等响曲线调整时，ASSR 的幅度与音调频率无关。幅度也不取决于前一个音调的存在或前一个音调的频率差异。当 AM 音调的声级随音调频率在 440-990 Hz 的相同范围内变化时，ASSR 的幅度以与声级成比例的方式变化。这些特征有利于在研究听觉皮层中听觉信息的时间处理时使用 ASSR。由短音序列引起的 ASSR 缺乏适应可能归因于初级听觉皮层中被广泛接受的磁 ASSR 发生器的神经活动。
