PHYSIOLOGICAL-MECHANISMS OF PSYCHOPHYSICAL MASKING - OBSERVATIONS FROM AUDITORY-NERVE FIBERS
PHYSIOLOGICAL-MECHANISMS OF PSYCHOPHYSICAL MASKING - OBSERVATIONS FROM AUDITORY-NERVE FIBERS
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DOI：
10.1121/1.398891
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发表时间：
1990-02-01
影响因子：
2.4
通讯作者：
DELGUTTE, B
中科院分区：
文献类型：
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作者：
DELGUTTE, B
掩蔽可能是由于掩蔽器产生的激励沿着耳蜗传播到音调信号的位置，或者是由于掩蔽器抑制了对信号的响应。为了确定这两种机制对音调掩蔽的贡献，使用与心理物理学相同的刺激范式和检测标准在麻醉猫中测量听觉神经纤维的掩蔽阈值。通过将同时掩蔽的阈值与类似于脉动阈值的非同时掩蔽技术的阈值进行比较来识别抑制性掩蔽。这些非同时阈值不包括抑制对掩蔽的贡献，因为抑制仅发生在时间重叠的刺激上。对于每个掩蔽和信号频率，具有最低（或“最佳”）掩蔽阈值的纤维的特征频率（CF）稍微位于掩蔽频率相对于信号频率的相反侧，这与异频聆听的心理物理现象一致。针对信号频率的最佳掩蔽阈值的模式类似于心理物理掩蔽模式，因为它们显示出接近掩蔽器的信号频率的最大值，并且偏向高频。掩蔽被发现既具有兴奋性又具有抑制性，两种机制的相对贡献取决于信号和掩蔽之间的频率间隔。对于远高于掩蔽信号的信号频率，抑制掩蔽很大。对于这些条件，同时阈值随着掩蔽水平的增长比非同时阈值增长得更快，这表明掩蔽的向上传播主要是由于抑制的增长而不是激励的增长。
Masking might be due either to the spread of the excitation produced by the masker to the place of the tone signal along the cochlea or to the suppression of the response to the signal by the masker. In order to identify the contributions of these two mechanisms to tone-on-tone masking, masked thresholds of auditory-nerve fibers were measured in anesthetized cats using the same stimulus paradigms and detection criteria as in psychophysics. Suppressive masking was identified by comparing thresholds for simultaneous masking with those for a nonsimultaneous masking technique resembling pulsation thresholds. These nonsimultaneous thresholds do not include the contribution of suppression to masking because suppression only occurs for stimuli that overlap in time. For each masker and signal frequency, the fibers with the lowest (or "best") masked thresholds had characteristic frequencies (CF) slightly on the opposite side of the masker frequency with respect to the signal frequency, consistent with the psychophysical phenomenon of off-frequency listening. Patterns of best masked thresholds against signal frequency resembled psychophysical masking patterns in that they showed a maximum for signal frequencies close to the masker, and a skew toward high frequencies. Masking was found to be both excitatory and suppressive, with the relative contribution of the two mechanisms depending on the frequency separation between signal and masker. Suppressive masking was large for signal frequencies well above the masker. For these conditions, simultaneous thresholds grew more rapidly with masker level than did nonsimultaneous thresholds, suggesting that the upward spread of masking is largely due to the growth of suppression rather than to that of excitation.