Greenberg S, Marsh J T, Brown W S, Smith J C
Hear Res. 1987;25(2-3):91-114. doi: 10.1016/0378-5955(87)90083-9.
The neural basis of low pitch was investigated in the present study by recording a brainstem potential from the scalp of human subjects during presentation of complex tones which evoke a variable sensation of pitch. The potential recorded, the frequency-following response (FFR), reflects the temporal discharge activity of auditory neurons in the upper brainstem pathway. It was used as an index of neural periodicity in order to determine the extent to which the low pitch of complex tones is encoded in the temporal discharge activity of auditory brainstem neurons. A tone composed of harmonics of a common fundamental produces a sensation of pitch equal to that of the 'missing' fundamental. Such signals generate brainstem potentials which are spectrally similar to FFR recorded in response to sinusoidal signals equal in frequency to the missing fundamental. Both types of signals generate FFR which are periodic, with a frequency similar to the perceived pitch of the stimuli. It is shown that the FFR to the missing fundamental is not the result of a distortion product by recording FFR to a complex signal in the presence of low-frequency bandpass noise. Neither is the FFR the result of neural synchronization to the waveform envelope modulation pattern. This was determined by recording FFR to inharmonic and quasi-frequency-modulated signals. It was also determined that the 'existence region' for FFR to the missing fundamental lies below 2 kHz and that the most favorable spectral region for FFR to complex tones is between 0.5 and 1.0 kHz. These results are consistent with the hypothesis that far-field-recorded FFR does reflect neural activity germane to the processing of low pitch and that such pitch-relevant activity is based on the temporal discharge patterns of neurons in the upper auditory brainstem pathway.
在本研究中，通过在向人类受试者头皮记录脑干电位来探究低音调的神经基础，这些受试者在呈现复合音调时会产生不同的音高感觉。所记录的电位，即频率跟随反应（FFR），反映了上脑干通路中听觉神经元的时间放电活动。它被用作神经周期性的指标，以确定复合音调的低音调在听觉脑干神经元的时间放电活动中被编码的程度。由共同基频的谐波组成的音调会产生与“缺失”基频相等的音高感觉。此类信号产生的脑干电位在频谱上与记录到的对频率等于缺失基频的正弦信号做出反应的FFR相似。这两种类型的信号都会产生具有周期性的FFR，其频率与刺激的感知音高相似。结果表明，通过在存在低频带通噪声的情况下记录对复合信号的FFR，可知对缺失基频的FFR不是失真产物的结果。FFR也不是神经与波形包络调制模式同步的结果。这是通过记录对非谐波和准频率调制信号的FFR来确定的。还确定了对缺失基频的FFR的“存在区域”低于2kHz，并且对复合音调的FFR最有利的频谱区域在0.5至1.0kHz之间。这些结果与以下假设一致，即远场记录的FFR确实反映了与低音调处理相关的神经活动，并且这种与音高相关的活动基于上听觉脑干通路中神经元的时间放电模式。
