Cortical fMRI activation to sequences of tones alternating in frequency: Relationship to perceived rate and streaming
Cortical fMRI activation to sequences of tones alternating in frequency: Relationship to perceived rate and streaming
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DOI：
10.1152/jn.00788.2006
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发表时间：
2007-03-01
影响因子：
2.5
通讯作者：
Oxenham, Andrew J.
中科院分区：
文献类型：
--
作者：
Wilson, E. Courtenay;Melcher, Jennifer R.;Oxenham, Andrew J.
人类听者在报告他们对由0、1/8、1或20个半音分隔的交变频率音调序列的感知时，被功能成像。我们的目标是确定听觉皮质的功能磁共振成像(FMRI)激活是否随着频率分离而变化，这种变化可以根据刺激的感知速率来预测。在零间隔和小间隔时，音调通常作为单个流被听到，其感知速率等于物理音调呈现速率。听觉皮质的fMRI激活有明显的阶段性，在序列开始和偏移时显示明显的峰值。在较大的频率间隔下，较高和较低频率的音调可感知地分成两个流，每个流的速率等于总音调呈现速率的一半。在这些条件下，听觉皮质中的fMRI激活在整个序列持续时间内更持续，并且在幅度和范围上更大。随着频率间隔和感知速率的变化，fMRI激活的相位到持续的变化与序列的物理速率的变化所产生的影响相当并且一致，并且远远大于改变其他物理刺激变量所产生的影响，例如声级或带宽。我们认为，fMRI激活随频率分离的变化背后的神经活动有助于编码共同出现的感知速率变化和声音序列到听觉流中的感知组织。
Human listeners were functionally imaged while reporting their perception of sequences of alternating-frequency tone bursts separated by 0, 1/8, 1, or 20 semitones. Our goal was to determine whether functional magnetic resonance imaging ( fMRI) activation of auditory cortex changes with frequency separation in a manner predictable from the perceived rate of the stimulus. At the null and small separations, the tones were generally heard as a single stream with a perceived rate equal to the physical tone presentation rate. fMRI activation in auditory cortex was appreciably phasic, showing prominent peaks at the sequence onset and offset. At larger-frequency separations, the higher- and lower-frequency tones perceptually separated into two streams, each with a rate equal to half the overall tone presentation rate. Under those conditions, fMRI activation in auditory cortex was more sustained throughout the sequence duration and was larger in magnitude and extent. Phasic to sustained changes in fMRI activation with changes in frequency separation and perceived rate are comparable to, and consistent with, those produced by changes in the physical rate of a sequence and are far greater than the effects produced by changing other physical stimulus variables, such as sound level or bandwidth. We suggest that the neural activity underlying the changes in fMRI activation with frequency separation contribute to the coding of the co-occurring changes in perceived rate and perceptual organization of the sound sequences into auditory streams.