Xue J T, Kim C B, Moore R J, Spear P D
Department of Psychology, University of Wisconsin, Madison 53706.
Vis Neurosci. 1994 Nov-Dec;11(6):1059-76. doi: 10.1017/s095252380000688x.
The superior colliculus (SC) projects to all layers of the cat's lateral geniculate nucleus (LGN) and thus is in a position to influence information transmission through the LGN. We investigated the function of the tecto-geniculate pathway by studying the responses of cat LGN neurons before, during, and after inactivating the SC with microinjections of lidocaine. The LGN cells were stimulated with drifting sine-wave gratings that varied in spatial frequency and contrast. Among 71 LGN neurons that were studied, 53 showed a statistically significant change in response during SC inactivation. Control experiments with mock injections indicated that some changes could be attributed to slow waxing and waning of responsiveness over time. However, this could not account for all of the effects of SC inactivation that were observed. Forty cells showed changes that were attributed to the removal of tecto-geniculate influences. About equal numbers of cells showed increases (22 cells) and decreases (18 cells) in some aspect of their response to visual stimuli during SC inactivation. The proportion of cells that showed tecto-geniculate influences was somewhat higher in the C layers (68% of the cells) than in the A layers (44% of the cells). In addition, among cells that showed a significant change in maximal response to visual stimulation, the change was larger for cells in the C layers (64% average change) than in the A layers (26% average change) and it was larger for W cells (61% average change) than for X and Y cells (29% average change). Nearly all of the X cells that showed changes had an increase in response, and nearly all of the Y cells had a decrease in response. In addition, across all cell classes, 80% of the cells with receptive fields < 15 deg from the area centralis had an increase in response, and 80% of the cells with receptive fields > or = 15 deg from the area centralis had a decrease in response. None of the LGN cells had significant changes in spatial resolution, and only three cells had changes in optimal spatial frequency. Ten cells had a change in contrast threshold, 25 cells had a change in contrast gain, and 29 cells had a change in the maximal response to a high-contrast stimulus. Thus, our results suggest that the tecto-geniculate pathway has little or no effect on spatial processing by LGN neurons. Rather, the major influence is on maximal response levels and the relationship between response and stimulus contrast.(ABSTRACT TRUNCATED AT 400 WORDS)
上丘（SC）投射到猫的外侧膝状体核（LGN）的所有层，因此能够影响通过LGN的信息传递。我们通过研究在向SC中微量注射利多卡因使其失活之前、期间和之后猫LGN神经元的反应，来探究顶盖-膝状体通路的功能。用空间频率和对比度不同的漂移正弦波光栅刺激LGN细胞。在研究的71个LGN神经元中，53个在SC失活期间反应有统计学上的显著变化。假注射的对照实验表明，一些变化可归因于反应性随时间的缓慢增强和减弱。然而，这并不能解释所观察到的SC失活的所有效应。40个细胞的变化归因于顶盖-膝状体影响的消除。在SC失活期间，对视觉刺激反应的某些方面显示增加（22个细胞）和减少（18个细胞）的细胞数量大致相等。显示顶盖-膝状体影响的细胞比例在C层（68%的细胞）略高于A层（44%的细胞）。此外，在对视觉刺激的最大反应有显著变化的细胞中，C层细胞的变化（平均变化64%）大于A层细胞（平均变化26%），W细胞的变化（平均变化61%）大于X和Y细胞（平均变化29%）。几乎所有显示变化的X细胞反应增强，几乎所有的Y细胞反应减弱。此外，在所有细胞类别中，接受野距离中央凹<15度的细胞中有80%反应增强，接受野距离中央凹≥15度的细胞中有80%反应减弱。LGN细胞的空间分辨率均无显著变化，只有三个细胞的最佳空间频率有变化。10个细胞的对比度阈值有变化，25个细胞的对比度增益有变化，29个细胞对高对比度刺激的最大反应有变化。因此，我们的结果表明，顶盖-膝状体通路对LGN神经元的空间处理几乎没有影响。相反，主要影响在于最大反应水平以及反应与刺激对比度之间的关系。（摘要截断于400字）
