Murphy P C, Sillito A M
Department of Visual Science, Institute of Ophthalmology, London, UK.
Nature. 1987;329(6141):727-9. doi: 10.1038/329727a0.
In the feline visual system, neurons exhibiting sensitivity to the length of a moving contour were first observed in the cortex and described as 'hypercomplex cells'. In these cells an increase in stimulus length beyond an optimal value leads to a rapid decline in response. This decline has been attributed to an intracortical inhibitory input which may be driven by layer VI cells with very long receptive fields. It is now clear, however, that cells in the dorsal lateral geniculate nucleus (dLGN), exhibit a degree of length tuning similar to that of cortical 'hypercomplex cells', suggesting that this response property could be generated subcortically. Alternatively, as the dLGN receives a massive corticofugal projection from layer VI cells in the visual cortex, it is possible that this input has a function in generating length tuning in the dLGN. We have investigated this issue by comparing the length tuning of dLGN cells with and without corticofugal feedback. The data show that corticofugal feedback makes a highly significant contribution to the length tuning of dLGN cells. This raises the possibility that length tuning is an emergent property of the geniculo-cortical loop.
在猫的视觉系统中，最早在皮层中观察到对移动轮廓长度敏感的神经元，并将其描述为“超复杂细胞”。在这些细胞中，刺激长度超过最佳值会导致反应迅速下降。这种下降被归因于皮层内抑制性输入，它可能由具有很长感受野的VI层细胞驱动。然而，现在很清楚的是，背外侧膝状核（dLGN）中的细胞表现出与皮层“超复杂细胞”相似程度的长度调谐，这表明这种反应特性可能在皮层下产生。或者，由于dLGN从视觉皮层的VI层细胞接收大量的皮质反馈投射，这种输入有可能在dLGN中产生长度调谐方面发挥作用。我们通过比较有和没有皮质反馈时dLGN细胞的长度调谐来研究这个问题。数据表明，皮质反馈对dLGN细胞的长度调谐有非常显著的贡献。这增加了长度调谐是膝状体 - 皮层环路的一种涌现特性的可能性。
