Ross Bernhard, Draganova Rossitza, Picton Terence W, Pantev Christo
Institute of Biomagnetism and Biosignalanalysis, University Hospital, Kardinal von Galen Ring 10, 48129 Münster, Germany.
Hear Res. 2003 Dec;186(1-2):57-68. doi: 10.1016/s0378-5955(03)00299-5.
Auditory steady-state responses (ASSR) to amplitude modulated (AM) tones with carrier frequencies between 250 and 4000 Hz and modulation frequencies near 40 Hz were recorded using a 37-channel neuro-magnetometer placed above the auditory cortex contralateral to the stimulated right ear. The ASSR sources were likely in the primary auditory cortex, located more anteriorly and more medially than the N1m sources. The ASSR amplitude decreased with increasing carrier frequency, the amplitude at 250 Hz being three times larger than at 4000 Hz. The amplitude of the ASSR to a test sound decreased in the presence of an interfering second AM sound. This suppression of the ASSR to the test stimulus was greater when the carrier frequency of the interfering stimulus was higher than that of the test tone and was greater when the test stimulus had a lower carrier frequency. Similar frequency specificity was observed when the interfering sound was a non-modulated pure tone. These results differ from those found for the ASSR elicited by modulation frequencies above 80 Hz or for the transient brainstem and middle-latency responses and suggest substantial interactions between phase-locked activities at the level of the primary auditory cortex.
使用放置在受刺激右耳对侧听觉皮层上方的37通道神经磁强计，记录了载波频率在250至4000赫兹之间且调制频率接近40赫兹的调幅（AM）音的听觉稳态反应（ASSR）。ASSR源可能位于初级听觉皮层，比N1m源更靠前且更靠内侧。ASSR幅度随载波频率增加而降低，250赫兹时的幅度比4000赫兹时大三倍。在存在干扰性的第二个调幅声音时，对测试声音的ASSR幅度会降低。当干扰刺激的载波频率高于测试音的载波频率时，对测试刺激的ASSR抑制作用更大；当测试刺激的载波频率较低时，这种抑制作用也更大。当干扰声音为非调制纯音时，观察到了类似的频率特异性。这些结果与由高于80赫兹的调制频率引发的ASSR或瞬态脑干和中潜伏期反应的结果不同，表明在初级听觉皮层水平上锁相活动之间存在大量相互作用。
