Winslow R L, Sachs M B
J Neurophysiol. 1987 Apr;57(4):1002-21. doi: 10.1152/jn.1987.57.4.1002.
The discharge rates of single auditory-nerve fibers responding to best-frequency (BF) tones of varying level presented simultaneously with fixed level broadband noise were recorded with and without electrical stimulation of the crossed olivocochlear bundle (COCB). In the absence of COCB stimulation, monotonic increases in noise level produce monotonic increases in the low-level noise-driven response rate of auditory nerve fibers. As a result of adaptation, these increases in noise-driven response rate produce monotonic decreases in saturation discharge rate. At high noise levels, these compressive effects may eliminate the differential rate response of auditory nerve fibers to BF tones. COCB stimulation can restore this differential rate response by producing large decreases in noise-driven response rate and large increases in saturation discharge rate. In backgrounds of quiet, COCB stimulation is known to shift the dynamic range of single auditory nerve fiber BF tone responses to higher stimulus levels. In the presence of background noise, COCB stimulation produces upward shift of dynamic range, which decreases with increasing noise level. At high noise levels, COCB-induced decompression of rate-level functions may occur with little or no dynamic range shift. This enables auditory nerve fibers to signal changes in tone level with changes in discharge rate at lower signal-to-noise ratios than would be possible otherwise. Broadband noise also produces upward shift of the dynamic range of single auditory nerve fiber BF tone response. Noise-induced dynamic range shift of BF tone response was measured as a function of noise level with and without COCB stimulation. COCB stimulation elevates the threshold of noise-induced dynamic range shift. This shift is thought to result from two-tone rate suppression. Increases in the threshold of noise-induced shift due to COCB stimulation therefore suggests an interaction between the mechanism of two-tone rate suppression and the mechanism by which COCB stimulation produces dynamic range shift. These interactions were further investigated by recording auditory nerve fiber rate responses to fixed-level BF excitor tones presented simultaneously with fixed-frequency variable level suppressor tones. Rate responses were recorded with and without COCB stimulation. Experimental results were quantified using a phenomenological model of two-tone rate suppression presented by Sachs and Abbas.
在有或没有交叉橄榄耳蜗束（COCB）电刺激的情况下，记录了单根听神经纤维对不同强度的最佳频率（BF）纯音与固定强度宽带噪声同时呈现时的放电率。在没有COCB刺激的情况下，噪声水平的单调增加会使听神经纤维由低水平噪声驱动的反应率单调增加。由于适应作用，这些由噪声驱动的反应率增加会使饱和放电率单调降低。在高噪声水平下，这些压缩效应可能会消除听神经纤维对BF纯音的差异率反应。COCB刺激可通过大幅降低由噪声驱动的反应率和大幅提高饱和放电率来恢复这种差异率反应。在安静的背景下，已知COCB刺激会将单根听神经纤维BF纯音反应的动态范围转移到更高的刺激水平。在存在背景噪声的情况下，COCB刺激会使动态范围向上移动，且随着噪声水平的增加而减小。在高噪声水平下，COCB诱导的率-级函数减压可能发生，而动态范围几乎没有或没有移动。这使得听神经纤维能够在比其他情况更低的信噪比下，通过放电率的变化来信号化音调水平的变化。宽带噪声也会使单根听神经纤维BF纯音反应的动态范围向上移动。测量了有和没有COCB刺激时，BF纯音反应的噪声诱导动态范围移动与噪声水平的函数关系。COCB刺激提高了噪声诱导动态范围移动的阈值。这种移动被认为是由双音率抑制引起的。因此，由于COCB刺激导致的噪声诱导移动阈值的增加表明双音率抑制机制与COCB刺激产生动态范围移动的机制之间存在相互作用。通过记录听神经纤维对与固定频率可变强度抑制音同时呈现的固定强度BF激励音的率反应，进一步研究了这些相互作用。在有和没有COCB刺激的情况下记录率反应。使用Sachs和Abbas提出的双音率抑制现象学模型对实验结果进行了量化。
