Uhlrich D J, Tamamaki N, Sherman S M
Department of Neurobiology, State University of New York, Stony Brook 11794-5230.
Proc Natl Acad Sci U S A. 1990 Apr;87(7):2560-3. doi: 10.1073/pnas.87.7.2560.
The visual pathway from retina through the lateral geniculate nucleus to visual cortex in the cat is comprised of several parallel neuronal streams that independently analyze different aspects of the visual scene. The best known of these are the X and Y pathways that relay through the geniculate A laminae. Recent receptive-field studies of retinal and geniculate neurons suggest that there is a further elaboration of cell types at the level of the lateral geniculate nucleus. That is, two types of geniculate X cells with different temporal patterns of responses to visual stimuli are recognized, one with "nonlagged" features, exhibiting shorter response latencies and another with "lagged" features; all retinal X cells are nonlagged. We asked whether nonlagged and lagged responses represent different cell classes or two response modes of the same cells, perhaps under the control of nonretinal afferents to these relay cells. Accordingly, we studied the effects on appropriate receptive-field properties of electrical activation of the midbrain parabrachial region, which is a major nonretinal input to relay cells. Such parabrachial stimulation made each of the eight lagged X cells much more like nonlagged cells, and this stimulation completely transformed the lagged response profiles of six of the eight cells to nonlagged. We thus conclude that the property of lagged responsiveness, which is an emergent property of the lateral geniculate nucleus, is a different response mode of the same cells that can also display nonlagged responses, rather than representing different cell classes; furthermore, this switching between response modes is, at least partly, under the control of afferents from the parabrachial region.
在猫中，从视网膜经外侧膝状体核至视觉皮层的视觉通路由几条并行的神经元流组成，这些神经元流独立分析视觉场景的不同方面。其中最著名的是通过膝状体A层中继的X和Y通路。最近对视网膜和膝状体神经元的感受野研究表明，在外侧膝状体核水平上细胞类型有进一步的细化。也就是说，识别出了两种对视觉刺激具有不同时间反应模式的膝状体X细胞，一种具有“非滞后”特征，表现出较短的反应潜伏期，另一种具有“滞后”特征；所有视网膜X细胞都是非滞后的。我们询问非滞后和滞后反应是代表不同的细胞类别还是同一细胞的两种反应模式，或许是在这些中继细胞的非视网膜传入神经的控制下。因此，我们研究了对中脑臂旁区域进行电激活对适当感受野特性的影响，中脑臂旁区域是中继细胞的主要非视网膜输入。这种臂旁刺激使八个滞后X细胞中的每一个都更像非滞后细胞，并且这种刺激将八个细胞中的六个的滞后反应模式完全转变为非滞后。因此我们得出结论，滞后反应特性作为外侧膝状体核的一种涌现特性，是同一细胞的一种不同反应模式，该细胞也可以表现出非滞后反应，而不是代表不同的细胞类别；此外，这种反应模式之间的转换至少部分受臂旁区域传入神经的控制。
