Visual response latencies of magnocellular and parvocellular LGN neurons in macaque monkeys
Visual response latencies of magnocellular and parvocellular LGN neurons in macaque monkeys
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DOI：
10.1017/s0952523899156177
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发表时间：
1999-01-01
影响因子：
1.9
通讯作者：
Noerager, BD
中科院分区：
文献类型：
--
作者：
Maunsell, JHR;Ghose, GM;Noerager, BD
通过 LGN 的大细胞层传递的信号在轴突上传播，其传导速度比通过小细胞层传递的信号更快。因此，大细胞信号可能明显先于小细胞信号到达大脑皮层。然而，仅根据轴突传导速度无法准确预测这两个通道的相对速度。其他因素，例如大细胞和小细胞通道以及为其提供营养的视网膜回路的不同程度的收敛，可能会影响大细胞和小细胞信号激活皮质神经元所需的时间。我们研究了大细胞和细细胞通道介导的视觉反应的相对时间。我们分别记录了两只麻醉猴子 LGN 中的 78 个大细胞神经元和 80 个小细胞神经元。测量了不同强度的小光点的视觉反应延迟。在各种刺激强度下，最快的大细胞反应延迟比最快的小细胞反应延迟约 10 毫秒。由于细小细胞神经元的数量远多于大细胞神经元，因此皮层的收敛可能会通过允许小细胞信号比基于单个小细胞神经元的反应的预期更快地产生可检测的反应来减少大细胞的优势。基于使用从 LGN 收集的神经生理学数据的简单模型进行的分析表明，皮层的收敛可以消除或逆转大细胞优势。这一观察结果对基于反应时间的神经元顺序关系做出的推论提出了质疑。
Signals relayed through the magnocellular layers of the LGN travel on axons with faster conduction speeds than those relayed through the parvocellular layers. As a result, magnocellular signals might reach cerebral cortex appreciably before parvocellular signals. The relative speed of these two channels cannot be accurately predicted based solely on axon conduction speeds, however. Other factors, such as different degrees of convergence in the magnocellular and parvocellular channels and the retinal circuits that feed them, can affect the time it takes for magnocellular and parvocellular signals to activate cortical neurons. We have investigated the relative timing of visual responses mediated by the magnocellular and parvocellular channels. We recorded individually from 78 magnocellular and 80 parvocellular neurons in the LGN of two anesthetized monkeys. Visual response latencies were measured for small spots of light of various intensities. Over a wide range of stimulus intensities the fastest magnocellular response latencies preceded the fastest parvocellular response latencies by about 10 ms. Because parvocellular neurons are far more numerous than magnocellular neurons, convergence in cortex could reduce the magnocellular advantage by allowing parvocellular signals to generate detectable responses sooner than expected based on the responses of individual parvocellular neurons. An analysis based on a simple model using neurophysiological data collected from the LGN shows that convergence in cortex could eliminate or reverse the magnocellular advantage. This observation calls into question inferences that have been made about ordinal relationships of neurons based on timing of responses.