Frequency selectivity of layer II stellate cells in the medial entorhinal cortex
Frequency selectivity of layer II stellate cells in the medial entorhinal cortex
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DOI：
10.1152/jn.00598.2002
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发表时间：
2002-11-01
影响因子：
2.5
通讯作者：
White, JA
中科院分区：
文献类型：
--
作者：
Haas, JS;White, JA
在电生理学上，内侧内嗅皮层（MEC）第二层的星状细胞（SC）的特点是固有的4至12 Hz的阈下振荡。这些振荡被认为是施加一种缓慢的周期性放电模式，可能有助于体内海马旁θ节律。使用系统不同的频率内容的刺激，我们研究了阈上和阈下的SC反应，目的是了解他们的独特特征如何塑造这些反应。在重复呈现相同的伪随机刺激的反应中，SC中的尖峰响应的可靠性（可重复性）关键地取决于刺激的频率内容。可靠性是最佳的刺激与更大比例的功率在4至12赫兹范围。这些结果的最简单的机械解释是，节律性阈下膜机制与包含4- 12-Hz频带中的显著功率的输入共振，导致更大的阈下偏移，从而增强可靠性。然而，对响应的仔细检查排除了这种解释：SC确实显示出明显的阈下共振（即，具有特定频率内容的输入的选择性放大），而同时显示出响应于可靠性实验中使用的伪随机刺激的亚阈值共振的缺乏。我们的研究结果支持一个模型，具有独特的输入输出关系下的阈下和阈上条件。对于阈上刺激，SC尖峰似乎最能反映θ（4-12 Hz）频带中的输入功率量。对于阈下刺激，我们假设SC中阈下θ范围振荡的幅度反映了输入的所有频率的总功率。
Electrophysiologically, stellate cells (SCs) from layer II of the medial entorhinal cortex (MEC) are distinguished by intrinsic 4- to 12-Hz subthreshold oscillations. These oscillations are thought to impose a pattern of slow periodic firing that may contribute to the parahippocampal theta rhythm in vivo. Using stimuli with systematically differing frequency content, we examined supra- and subthreshold responses in SCs with the goal of understanding how their distinctive characteristics shape these responses. In reaction to repeated presentations of identical, pseudo-random stimuli, the reliability (repeatability) of the spiking response in SCs depends critically on the frequency content of the stimulus. Reliability is optimal for stimuli with a greater proportion of power in the 4- to 12-Hz range. The simplest mechanistic explanation of these results is that rhythmogenic subthreshold membrane mechanisms resonate with inputs containing significant power in the 4- to 12-Hz band, leading to larger subthreshold excursions and thus enhanced reliability. However, close examination of responses rules out this explanation: SCs do show clear subthreshold resonance (i.e., selective amplification of inputs with particular frequency content) in response to sinusoidal stimuli, while simultaneously showing a lack of subthreshold resonance in response to the pseudo-random stimuli used in reliability experiments. Our results support a model with distinctive input-output relationships under subthreshold and suprathreshold conditions. For suprathreshold stimuli, SC spiking seems to best reflect the amount of input power in the theta (4-12 Hz) frequency band. For subthreshold stimuli, we hypothesize that the magnitude of subthreshold theta-range oscillations in SCs reflects the total power, across all frequencies, of the input.