On the prediction of sweep rate and directional selectivity for FM sounds from two-tone interactions in the inferior colliculus
On the prediction of sweep rate and directional selectivity for FM sounds from two-tone interactions in the inferior colliculus
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DOI：
10.1016/j.heares.2005.07.005
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发表时间：
2005-12-01
期刊：
影响因子：
2.8
通讯作者：
O'Neill, WE
中科院分区：
文献类型：
--
作者：
Brimijoin, WO;O'Neill, WE
双音刺激传统上被用来揭示听觉光谱感受野的抑制区域，特别是对于自发频率低的神经元。这些技术揭示了不同的频率如何激发或抑制细胞对兴奋性频率的反应，但通常是在固定的掩蔽探针时间间隔进行评估。我们使用了这种方法的变化，以确定是否双音spectrotemporal的相互作用可以占率依赖的方向选择性的频率调制（FM）在胡子蝙蝠下丘（IC）。首先，我们量化了在2到64 ins的6个扫描持续时间内，对以单元特征频率（CF）为中心的向上和向下扫描、线性、固定带宽FM音调的响应。然后，为了研究对扫描中包含的瞬时频率的响应如何在时间上相互作用，我们改变了与固定的4-ms CF探测音配对的简短（4 ms）“调节器”音的频率和相对起始。我们构建了“条件反应区”（CRA）描绘区域的抑制和促进的探测音所造成的条件音。我们将CRA分类为主要兴奋性（40.9%）、抑制性（22.7%）或混合性（36.4%）。为了生成FM响应预测，CRA乘以用于评估对FM的响应的相同扫描的频谱图。FM率和方向性的预测是准确的，我们的标准在约20%的单位。相反，来自其余单元的CRA未能准确地预测FM响应，这表明大多数IC单元对FM扫描的响应不同于它们对与这些扫描中包含的瞬时频率匹配的音调对的响应。FM方向性模型的这些结果的影响进行了讨论。(c)2005 Elsevier B. V.保留所有权利。
Two-tone stimuli have traditionally been used to reveal regions of inhibition in auditory spectral receptive fields, particularly for neurons with low spontaneous rates. These techniques reveal how different frequencies excite or suppress the response to an excitatory frequency of a cell, but have often been assessed at a fixed masker-probe time interval. We used a variation of this methodology to determine whether two-tone spectrotemporal interactions can account for rate-dependent directional selectivity for frequency modulations (FM) in the mustached bat inferior colliculus (IC). First, we quantified the response to upward and downward sweeping, linear, fixed-bandwidth FM tones centered at a unit's characteristic frequency (CF) at 6 sweep durations ranging from 2 to 64 ins. Then, to examine how responses to instantaneous frequencies contained within the sweeps might interact in time, we varied the frequency and relative onset of a brief (4 ms) "conditioner" tone paired with a fixed 4-ms CF probe tone. We constructed "conditioned response areas" (CRA) depicting regions of suppression and facilitation of the probe tone caused by the conditioning tone. We classified the CRAs as predominantly excitatory (40.9%), inhibitory (22.7%), or mixed (36.4%). To generate FM response predictions, the CRAs were multiplied with spectrograms of the same sweeps used to assess response to FM. The predictions of FM rate and directionality were accurate by our criteria in approximately 20% of units. Conversely, the CRAs from the remaining units failed to predict FM responses as accurately, suggesting that most IC units respond differently to FM sweeps than they do to tone-pairs matched to the instantaneous frequencies contained in those sweeps. The implications of these results for models of FM directionality are discussed. (c) 2005 Elsevier B.V. All rights reserved.