Short-Term Depression, Temporal Summation, and Onset Inhibition Shape Interval Tuning in Midbrain Neurons
Short-Term Depression, Temporal Summation, and Onset Inhibition Shape Interval Tuning in Midbrain Neurons
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DOI：
10.1523/jneurosci.2299-14.2014
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发表时间：
2014-10-22
影响因子：
5.3
通讯作者：
Carlson, Bruce A.
中科院分区：
文献类型：
--
作者：
Baker, Christa A.;Carlson, Bruce A.
多种突触机制可以促进单神经元对感觉刺激的时间间隔的选择性。然而，这些机制如何相互作用以建立单神经元对体内感觉刺激时间模式的敏感性仍然未知。在这里，我们在一个电路中解决这个问题，该电路允许我们以行为相关的方式控制间隔调谐神经元的突触输入的精确时间模式。我们在用电传感脉冲序列刺激期间，从绦虫科弱电鱼 Brienomyrus brachyistius 的中脑神经元的多个电流钳位水平下获得了体内细胞内记录。为了揭示间隔调谐神经元的兴奋性和抑制性输入，我们估计了潜在反应的突触电导。我们发现所有间隔调节神经元的兴奋性和抑制性通路均出现短期抑制。短间隔选择性与在短间隔内抑制小于抑制的兴奋以及暂时总结兴奋有关。长间隔选择性与持久的起效抑制相关。我们在分别抵消时间求和和抑制的贡献后研究了调整，发现当两种机制都发挥作用时，神经元之间的区间选择性具有最大的多样性。此外，消除抑郁的影响会降低对间隔方向变化的敏感性。这些发现表明，抑郁的变化以及兴奋和抑制的总和有助于建立对通信信号中行为相关间隔的调整，并且抑郁有助于间隔序列的神经编码。这项工作首次揭示了短期可塑性和时间求和之间的相互作用如何介导清醒、行为动物的时间序列解码。
A variety of synaptic mechanisms can contribute to single-neuron selectivity for temporal intervals in sensory stimuli. However, it remains unknown how these mechanisms interact to establish single-neuron sensitivity to temporal patterns of sensory stimulation in vivo. Here we address this question in a circuit that allows us to control the precise temporal patterns of synaptic input to interval-tuned neurons in behaviorally relevant ways. We obtained in vivo intracellular recordings under multiple levels of current clamp from midbrain neurons in the mormyrid weakly electric fish Brienomyrus brachyistius during stimulation with electrosensory pulse trains. To reveal the excitatory and inhibitory inputs onto interval-tuned neurons, we then estimated the synaptic conductances underlying responses. We found short-term depression in excitatory and inhibitory pathways onto all interval-tuned neurons. Short-interval selectivity was associated with excitation that depressed less than inhibition at short intervals, as well as temporally summating excitation. Long-interval selectivity was associated with long-lasting onset inhibition. We investigated tuning after separately nullifying the contributions of temporal summation and depression, and found the greatest diversity of interval selectivity among neurons when both mechanisms were at play. Furthermore, eliminating the effects of depression decreased sensitivity to directional changes in interval. These findings demonstrate that variation in depression and summation of excitation and inhibition helps to establish tuning to behaviorally relevant intervals in communication signals, and that depression contributes to neural coding of interval sequences. This work reveals for the first time how the interplay between short-term plasticity and temporal summation mediates the decoding of temporal sequences in awake, behaving animals.