Distributed representation of tone frequency in highly decodable spatio-temporal activity in the auditory cortex
Distributed representation of tone frequency in highly decodable spatio-temporal activity in the auditory cortex
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DOI：
10.1016/j.neunet.2010.12.010
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发表时间：
2011-05-01
期刊：
影响因子：
7.8
通讯作者：
Takahashi, Hirokazu
中科院分区：
文献类型：
--
作者：
Funamizu, Akihiro;Kanzaki, Ryohei;Takahashi, Hirokazu
尽管音调频率的位置编码或音调位图在听觉皮层中已被广泛接受，但在中等或高声压水平下，音调诱发的激活变得不那么具有频率特异性。这意味着声音频率不是由一个简单的位置代码表示的，而是与焦点激活无关的信息在时空上的分布。在这项研究中，我们使用基于解码的分析，研究了麻醉大鼠听觉皮层的多单元活动，以阐明音调频率如何在时空神经模式中表示。我们尝试用支持向量机（SVM）递归特征消除（RFE）的具体实现——序列降维（SDR）来识别解码测试频率的最佳时空窗口模式。SDR选择了大约四分之一的窗口，SDR识别的窗口模式比空间模式（消除了时间结构）或高尖峰率模式（选择性提取了高尖峰率窗口）的解码效果要好得多。因此，测试频率也被编码在神经活动的时间和空间结构和低尖峰率窗口中。然而，SDR招募了比低尖峰率窗口更多的高尖峰率窗口，从而产生了高度分散的模式，这可能提供了识别能力的优势。对支持向量机权重的进一步研究表明，低尖峰率窗口在精细频率分化中发挥了重要作用。这些发现支持了听觉皮层在音调频率表征中采用分布式编码的假设，其中高尖峰率和低尖峰率活动相互补充。(C) 2011 Elsevier Ltd.版权所有。
Although the place code of tone frequency, or tonotopic map, has been widely accepted in the auditory cortex, tone-evoked activation becomes less frequency-specific at moderate or high sound pressure levels. This implies that sound frequency is not represented by a simple place code but that the information is distributed spatio-temporally irrespective of the focal activation. In this study, using a decoding-based analysis, we investigated multi-unit activities in the auditory cortices of anesthetized rats to elucidate how a tone frequency is represented in the spatio-temporal neural pattern. We attempted sequential dimensionality reduction (SDR), a specific implementation of recursive feature elimination (RFE) with support vector machine (SVM), to identify the optimal spatio-temporal window patterns for decoding test frequency. SDR selected approximately a quarter of the windows, and SDR-identified window patterns led to significantly better decoding than spatial patterns, in which temporal structures were eliminated, or high-spike-rate patterns, in which windows with high spike rates were selectively extracted. Thus, the test frequency is also encoded in temporal as well as spatial structures of neural activities and low-spike-rate windows. Yet, SDR recruited more high-spike-rate windows than low-spike-rate windows, resulting in a highly dispersive pattern that probably offers an advantage of discrimination ability. Further investigation of SVM weights suggested that low-spike-rate windows play significant roles in fine frequency differentiation. These findings support the hypothesis that the auditory cortex adopts a distributed code in tone frequency representation, in which high-and low-spike-rate activities play mutually complementary roles. (C) 2011 Elsevier Ltd. All rights reserved.