Mammalian octopus cells are direction selective to frequency sweeps by excitatory synaptic sequence detection.
Mammalian octopus cells are direction selective to frequency sweeps by excitatory synaptic sequence detection.
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DOI：
10.1073/pnas.2203748119
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发表时间：
2022-11
影响因子：
11.1
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中科院分区：
文献类型：
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有几类听觉脑干神经元具有极快的膜;它们被认为是巧合探测器，并且是编码声音快速时间波动的理想选择。在这些神经元中，由于记录困难，章鱼细胞可能是最不了解的。在这里，我们提供了全面的这些细胞在体内的细胞内记录，并发现，相反的预测符合检测，他们是方向选择FM扫描通过序列检测的机制。重要的是，序列检测和方向选择性在具有快速膜的生物物理模型中重建。由于它是一个简单但功能强大的操作，我们建议，序列检测可能是一个更普遍的机制，以提取时间信息比重合检测。章鱼细胞是哺乳动物耳蜗神经核的重要投射神经元，具有极快速的膜和宽频率调谐。它们被认为是符合探测器的主要例子，但在体内的特性很差。我们发现章鱼细胞对频率扫描方向有选择性，这是它们听觉神经输入中不存在的一个特征。在体内的细胞内记录显示，方向选择性并不来自跨频率重合检测，但取决于振幅和激活序列的听觉神经输入调谐到集群的热点频率。一个简单的生物物理章鱼细胞模型与真实的神经棘波列车兴奋重建方向选择性，通过相互作用的内在膜电导与激活序列的集群兴奋性输入。我们的结论是，章鱼细胞是序列探测器，敏感的时间模式，整个耳蜗频率通道。检测序列而不是重合是提取时间信息的一种简单得多但功能强大的操作。
Several classes of auditory brain stem neurons have extremely fast membranes; they are thought to be coincidence detectors and ideal for encoding rapid temporal fluctuations of sounds. Of those neurons, octopus cells are perhaps the least understood due to recording difficulties. Here, we provide comprehensive in vivo intracellular recordings of these cells and find that contrary to the prediction of coincidence detection, they are direction selective to FM sweeps via a mechanism of sequence detection. Importantly, sequence detection and direction selectivity are recreated in a biophysical model with fast membranes. As it is a simple but powerful operation, we propose that sequence detection may be a more general mechanism to extract temporal information than coincidence detection. Octopus cells are remarkable projection neurons of the mammalian cochlear nucleus, with extremely fast membranes and wide-frequency tuning. They are considered prime examples of coincidence detectors but are poorly characterized in vivo. We discover that octopus cells are selective to frequency sweep direction, a feature that is absent in their auditory nerve inputs. In vivo intracellular recordings reveal that direction selectivity does not derive from across-frequency coincidence detection but hinges on the amplitudes and activation sequence of auditory nerve inputs tuned to clusters of hot spot frequencies. A simple biophysical octopus cell model excited with real nerve spike trains recreates direction selectivity through interaction of intrinsic membrane conductances with the activation sequence of clustered excitatory inputs. We conclude that octopus cells are sequence detectors, sensitive to temporal patterns across cochlear frequency channels. The detection of sequences rather than coincidences is a much simpler but powerful operation to extract temporal information.
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