Instituto de Neurociencias de Castilla y León, Universidad de Salamanca, Salamanca, Spain.
Adv Exp Med Biol. 2013;787:47-54. doi: 10.1007/978-1-4614-1590-9_6.
In binaural listening, the two cochleae do not act as independent sound receptors; their functioning is linked via the contralateral medial olivo-cochlear reflex (MOCR), which can be activated by contralateral sounds. The present study aimed at characterizing the effect of a contralateral white noise (CWN) on psychophysical tuning curves (PTCs). PTCs were measured in forward masking for probe frequencies of 500 Hz and 4 kHz, with and without CWN. The sound pressure level of the probe was fixed across conditions. PTCs for different response criteria were measured by using various masker-probe time gaps. The CWN had no significant effects on PTCs at 4 kHz. At 500 Hz, by contrast, PTCs measured with CWN appeared broader, particularly for short gaps, and they showed a decrease in the masker level. This decrease was greater the longer the masker-probe time gap. A computer model of forward masking with efferent control of cochlear gain was used to explain the data. The model accounted for the data based on the assumption that the sole effect of the CWN was to reduce the cochlear gain by ∼6.5 dB at 500 Hz for low and moderate levels. It also suggested that the pattern of data at 500 Hz is the result of combined broad bandwidth of compression and off-frequency listening. Results are discussed in relation with other physiological and psychoacoustical studies on the effect of activation of MOCR on cochlear function.
在双耳聆听中，两个耳蜗并非作为独立的声音接收器发挥作用；它们的功能通过对侧内侧橄榄耳蜗反射（MOCR）相互连接，而对侧声音可以激活该反射。本研究旨在描述对侧白噪声（CWN）对心理物理调谐曲线（PTC）的影响。在正向掩蔽中测量了探针频率为 500 Hz 和 4 kHz 时的 PTC，有无 CWN 时均进行了测量。探针的声压级在不同条件下保持固定。通过使用不同的掩蔽-探针时间间隔，测量了不同响应标准的 PTC。在 4 kHz 时，CWN 对 PTC 没有显著影响。相比之下，在 500 Hz 时，使用 CWN 测量的 PTC 显得更宽，特别是在短时间间隔下，而且它们的掩蔽水平下降。掩蔽-探针时间间隔越长，下降幅度越大。使用带有传出控制耳蜗增益的正向掩蔽计算机模型来解释数据。该模型基于 CWN 的唯一作用是在低频和中频时将耳蜗增益降低约 6.5 dB 的假设来解释数据。它还表明，500 Hz 处的数据模式是压缩和离频聆听的宽带宽组合的结果。结果与关于 MOCR 激活对耳蜗功能影响的其他生理和心理声学研究进行了讨论。
