Loss of sensitivity in an analog neural circuit.
Loss of sensitivity in an analog neural circuit.
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DOI：
10.1523/jneurosci.5071-08.2009
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发表时间：
2009-03-11
期刊：
影响因子：
--
通讯作者：
Smith RG
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文献类型：
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作者：
Borghuis BG;Sterling P;Smith RG
在细胞的尖峰序列中检测到仅激活视网膜中一个神经节细胞的低对比度点，其灵敏度与行为检测的灵敏度大致相同。这与巴洛的提议是一致的，即神经节细胞和尖峰神经元的后期传输信息基本上不会丢失。然而，当考虑到所有神经前因素导致的敏感性丧失时，阈值附近的预测敏感性远远大于行为敏感性，这意味着大脑中的某个地方信息丢失了。我们假设损失主要发生在视网膜中，分级信号由模拟电路处理，以高速率和低代谢成本传输信息。为了测试这一点，我们构建了一个模型，其中包括体外哺乳动物视网膜的所有前神经损失，并评估该模型以预测视锥细胞输出的敏感性。记录突触后对视锥细胞（来自 A 型水平细胞）的分级反应，并与预测的神经前敏感性进行比较，我们发现第一个视觉突触的敏感性大幅下降（4.2 倍）。记录用同一点刺激的短暂神经节细胞的尖峰反应，我们发现第二个突触有类似的损失（3.5 倍）。总视网膜损失近似于已知的总体损失，支持这样的假设：从刺激到感知，阈值附近的大多数损失是视网膜。
A low contrast spot that activates just one ganglion cell in the retina is detected in the cell’s spike train with about the same sensitivity as it is detected behaviorally. This is consistent with Barlow’s proposal that the ganglion cell and later stages of spiking neurons transfer information essentially without loss. Yet, when losses of sensitivity by all preneural factors are accounted for, predicted sensitivity near threshold is considerably greater than behavioral sensitivity, implying that somewhere in the brain information is lost. We hypothesized that the losses occur mainly in the retina - where graded signals are processed by analog circuits that transfer information at high rates and low metabolic cost. To test this, we constructed a model that included all preneural losses for an in vitro mammalian retina, and evaluated the model to predict sensitivity at the cone output. Recording graded responses postsynaptic to the cones (from the type A horizontal cell) and comparing to predicted preneural sensitivity, we found substantial loss of sensitivity (4.2-fold) across the first visual synapse. Recording spike responses from brisk-transient ganglion cells stimulated with the same spot, we found a similar loss (3.5-fold) across the second synapse. The total retinal loss approximated the known overall loss, supporting the hypothesis that from stimulus to perception, most loss near threshold is retinal.