Holmes Emma, Purcell David W, Carlyon Robert P, Gockel Hedwig E, Johnsrude Ingrid S
Brain and Mind Institute, University of Western Ontario, Natural Sciences Centre, Room 120, London, ON, N6A 5B7, Canada.
School of Communication Sciences and Disorders, University of Western Ontario, London, ON, N6G 1H1, Canada.
J Assoc Res Otolaryngol. 2018 Feb;19(1):83-97. doi: 10.1007/s10162-017-0641-9. Epub 2017 Oct 2.
Directing attention to sounds of different frequencies allows listeners to perceive a sound of interest, like a talker, in a mixture. Whether cortically generated frequency-specific attention affects responses as low as the auditory brainstem is currently unclear. Participants attended to either a high- or low-frequency tone stream, which was presented simultaneously and tagged with different amplitude modulation (AM) rates. In a replication design, we showed that envelope-following responses (EFRs) were modulated by attention only when the stimulus AM rate was slow enough for the auditory cortex to track-and not for stimuli with faster AM rates, which are thought to reflect 'purer' brainstem sources. Thus, we found no evidence of frequency-specific attentional modulation that can be confidently attributed to brainstem generators. The results demonstrate that different neural populations contribute to EFRs at higher and lower rates, compatible with cortical contributions at lower rates. The results further demonstrate that stimulus AM rate can alter conclusions of EFR studies.
将注意力导向不同频率的声音，能让听众在混合声音中感知到感兴趣的声音，比如说话者的声音。目前尚不清楚皮层产生的频率特异性注意力是否会影响低至听觉脑干的反应。参与者关注高频或低频音流，这些音流同时呈现并标记有不同的调幅（AM）率。在一项重复设计中，我们发现，只有当刺激的调幅率足够慢，使听觉皮层能够追踪时，包络跟随反应（EFRs）才会受到注意力的调制，而对于调幅率更快的刺激则不然，后者被认为反映的是“更纯粹”的脑干源。因此，我们没有发现可以可靠地归因于脑干发生器的频率特异性注意力调制的证据。结果表明，不同的神经群体在不同速率下对EFRs有贡献，这与较低速率下的皮层贡献相一致。结果还表明，刺激的调幅率可以改变EFR研究的结论。
