Sparse representation of sounds in the unanesthetized auditory cortex.
Sparse representation of sounds in the unanesthetized auditory cortex.
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DOI：
10.1371/journal.pbio.0060016
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发表时间：
2008-01
期刊：
影响因子：
9.8
通讯作者：
Zador AM
中科院分区：
文献类型：
--
作者：
Hromádka T;Deweese MR;Zador AM
听觉皮质中的神经元群如何代表声刺激？虽然在麻醉的听觉皮质中，声音诱发的神经反应主要是瞬时的，但最近在非麻醉准备中的实验强调了具有其他反应特性的亚群。为了量化这些不同亚群在觉醒准备中的相对贡献，我们使用具有代表性的刺激集合估计了神经元种群中声音的表示。我们使用玻璃电极的细胞附着记录，这种方法的单个单位分离不依赖于神经元活动，以量化声音刺激(音调、调频扫描、白噪声脉冲和自然刺激)在清醒的头部固定大鼠的初级听觉皮质中参与的神经元的比例。我们发现，群体反应是稀疏的，刺激通常在任何时刻都会在不到5%的神经元中引发高放电率(20个尖峰/秒)。有些神经元的自发放电率很低(0.01次/秒)。在另一个极端，一些神经元驱动的频率超过了50次/秒。有趣的是，总体人口反应符合对数正态分布，而不是经常报道的指数分布。据我们所知，我们的结果代表了第一个量化证据，证明在未麻醉的听觉皮质中声音的稀疏表示。我们的结果与一个模型兼容，在这个模型中，大多数神经元大部分时间都是沉默的，并且表示是由高度活跃的神经元的小动态子集组成的。听觉皮质中的神经元群如何代表声音？虽然在麻醉的听觉皮质中，声音诱发的神经反应主要是瞬时的，但最近在非麻醉准备中的实验强调了具有其他反应特性的亚群。我们量化了这些不同亚群在清醒的头部固定大鼠的听觉皮质中的相对贡献。我们使用玻璃电极的细胞连接录音记录神经元活动-这种方法分离单个神经元不依赖于神经元活动-同时探测具有代表性的声音集合的神经元。因此，我们的数据解决了一个问题：对特定刺激措施的典型反应是什么？我们发现，群体反应是稀疏的，声音通常在任何时刻都会在不到5%的神经元中引发高活性。总体人口反应符合对数正态分布，而不是经常报道的指数分布。据我们所知，我们的结果代表了第一个量化证据，证明在未麻醉的听觉皮质中声音的稀疏表示。这些结果与一个模型相一致，在这个模型中，大多数神经元大部分时间都是沉默的，并且表示是由高度活跃的神经元的小动态子集组成的。未麻醉大鼠听皮层的膜片钳记录显示，群体对声音的反应很稀疏，大多数神经元大部分时间都是沉默的。
How do neuronal populations in the auditory cortex represent acoustic stimuli? Although sound-evoked neural responses in the anesthetized auditory cortex are mainly transient, recent experiments in the unanesthetized preparation have emphasized subpopulations with other response properties. To quantify the relative contributions of these different subpopulations in the awake preparation, we have estimated the representation of sounds across the neuronal population using a representative ensemble of stimuli. We used cell-attached recording with a glass electrode, a method for which single-unit isolation does not depend on neuronal activity, to quantify the fraction of neurons engaged by acoustic stimuli (tones, frequency modulated sweeps, white-noise bursts, and natural stimuli) in the primary auditory cortex of awake head-fixed rats. We find that the population response is sparse, with stimuli typically eliciting high firing rates (>20 spikes/second) in less than 5% of neurons at any instant. Some neurons had very low spontaneous firing rates (<0.01 spikes/second). At the other extreme, some neurons had driven rates in excess of 50 spikes/second. Interestingly, the overall population response was well described by a lognormal distribution, rather than the exponential distribution that is often reported. Our results represent, to our knowledge, the first quantitative evidence for sparse representations of sounds in the unanesthetized auditory cortex. Our results are compatible with a model in which most neurons are silent much of the time, and in which representations are composed of small dynamic subsets of highly active neurons. How do neuronal populations in the auditory cortex represent sounds? Although sound-evoked neural responses in the anesthetized auditory cortex are mainly transient, recent experiments in the unanesthetized preparation have emphasized subpopulations with other response properties. We quantified the relative contributions of these different subpopulations in the auditory cortex of awake head-fixed rats. We recorded neuronal activity using cell-attached recordings with a glass electrode—a method for which isolation of individual neurons does not depend on neuronal activity—while probing neurons with a representative ensemble of sounds. Our data therefore address the question: What is the typical response to a particular stimulus? We find that the population response is sparse, with sounds typically eliciting high activity in less than 5% of neurons at any instant. The overall population response was well described by a lognormal distribution, rather than the exponential distribution that is often reported. Our results represent, to our knowledge, the first quantitative evidence for sparse representations of sounds in the unanesthetized auditory cortex. These results are compatible with a model in which most neurons are silent much of the time, and in which representations are composed of small dynamic subsets of highly active neurons. Patch clamp recordings in the auditory cortex of unanesthetized rats reveal that the population response to sounds is sparse and that most neurons are silent most of the time.
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