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Cortical response selectivity derives from strength in numbers of synapses

机译：皮质响应选择性来自突触数量的强度

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摘要

Single neocortical neurons are driven by populations of excitatory inputs, which form the basis of neuronal selectivity to features of sensory input. Excitatory connections are thought to mature during development through activity-dependent Hebbian plasticity~(1), whereby similarity between presynaptic and postsynaptic activity selectively strengthens some synapses and weakens others~(2). Evidence in support of this process includes measurements of synaptic ultrastructure and in vitro and in vivo physiology and imaging studies~(3-8). These corroborating lines of evidence lead to the prediction that a small number of strong synaptic inputs drive neuronal selectivity, whereas weak synaptic inputs are less correlated with the somatic output and modulate activity overall~(6,7). Supporting evidence from cortical circuits, however, has been limited to measurements of neighbouring, connected cell pairs, raising the question of whether this prediction holds for a broad range of synapses converging onto cortical neurons. Here we measure the strengths of functionally characterized excitatory inputs contacting single pyramidal neurons in ferret primary visual cortex (V1) by combining in vivo two-photon synaptic imaging and post hoc electron microscopy. Using electron microscopy reconstruction of individual synapses as a metric of strength, we find no evidence that strong synapses have a predominant role in the selectivity of cortical neuron responses to visual stimuli. Instead, selectivity appears to arise from the total number of synapses activated by different stimuli. Moreover, spatial clustering of co-active inputs appears to be reserved for weaker synapses, enhancing the contribution of weak synapses to somatic responses. Our results challenge the role of Hebbian mechanisms in shaping neuronal selectivity in cortical circuits, and suggest that selectivity reflects the co-activation of large populations of presynaptic neurons with similar properties and a mixture of strengths.
机译：单一新皮质神经元由兴奋性输入的群体驱动，其构成了对感觉输入特征的神经元选择性的基础。通过依赖活动的Hebbian可塑性〜（1）在开发过程中被认为是成熟的，其中突触前和突触后活动之间的相似性选择性地增强了一些突触并削弱了其他突触〜（2）。支持该过程的证据包括突触超微结构和体外测量和体内生理学和成像研究的测量〜（3-8）。这些证据的证据导致预测少量强突触输入驱动神经元选择性，而弱突触输入与总体输出和调节活动的弱突出输入较小〜（6,7）。然而，来自皮质电路的证据仅限于相邻连接的细胞对的测量，提高了该预测是否具有在皮质神经元的广泛突触中保持的问题。在这里，我们通过在体内两光膜突触成像和后HOC电子显微镜中组合来测量与白叶初级视觉皮质（V1）中的单金字塔内神经元接触的功能表征兴奋性输入的优点。利用电子显微镜重建单个突触作为强度的指标，我们发现没有证据表明强烈的突触在皮质神经元对视觉刺激的反应的选择性中具有主要作用。相反，选择性似乎是由不同刺激激活的突触的总数出现。此外，共同主动输入的空间聚类似乎保留用于较弱的突触，增强弱突触对体细胞反应的贡献。我们的成果挑战了Hebbian机制在皮质电路中形成神经元选择性方面的作用，并表明选择性反映了具有相似性质和强度混合物的突触前神经元大群的共激化。

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  • 来源
    《Nature》 |2021年第7844期|111-114|共4页
  • 作者

    Benjamin Scholl; Connon I Thomas; Melissa A Ryan; Naomi Kamasawa; David Fitzpatrick;

  • 作者单位

    Functional Architecture and Development of Cerebral Cortex Max Planck Florida Institute for Neuroscience|Department of Neuroscience Perelman School of Medicine at the University of Pennsylvania;

    Electron Microscopy Core Facility Max Planck Florida Institute for Neuroscience;

    Electron Microscopy Core Facility Max Planck Florida Institute for Neuroscience;

    Electron Microscopy Core Facility Max Planck Florida Institute for Neuroscience;

    Functional Architecture and Development of Cerebral Cortex Max Planck Florida Institute for Neuroscience;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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