Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Neurosci. 2011 Jan 12;31(2):373-84. doi: 10.1523/JNEUROSCI.4738-10.2011.
We previously established a functional pathway extending from the superficial layers of the superior colliculus (SC) through the inferior pulvinar (PI) to cortical area MT in the primate (Macaca mulatta). Here, we characterized the signals that this pathway conveys to cortex by recording from pulvinar neurons that we identified by microstimulation as receiving input from SC and/or projecting to MT. The basic properties of these ascending-path PI neurons resembled those of SC visual neurons. Namely, they had brisk responses to spots of light, inhibitory surrounds, and relatively large receptive fields that increased with eccentricity, as well as minimal presaccadic activity. Beyond these basic properties, there were two salient results regarding the modulatory and motion signals conveyed by this ascending pathway. First, the PI neurons appeared to convey only a subset of the modulations found in the SC: they exhibited saccadic suppression, the inhibition of activity at the time of the saccade, but did not clearly show the attentional enhancement of the visual response seen in SC. Second, directional selectivity was minimal in PI neurons belonging to the ascending path but was significantly more prominent in PI neurons receiving input from MT. This finding casts doubt on earlier assumptions that PI provides directionally selective signals to MT and instead suggests that PI derives its selectivity from MT. The identification of this pathway and its transmitted activity establishes the first functional pathway from brainstem to cortex through pulvinar and makes it possible to examine its contribution to cortical visual processing, perception, and action.
我们之前建立了一个从灵长类动物（猕猴）上丘的浅层延伸到下丘（PI）再到皮质区 MT 的功能通路。在这里，我们通过记录我们通过微刺激确定的从 PI 接收来自 SC 和/或投射到 MT 的输入的神经元，来描述该通路向皮层传递的信号。这些上升路径 PI 神经元的基本特性与 SC 视觉神经元相似。也就是说，它们对光点、抑制性环绕和相对较大的感受野具有快速反应，随着离轴距离的增加而增加，并且几乎没有预眼跳活动。除了这些基本特性之外，关于该上升通路传递的调制和运动信号还有两个显著的结果。首先，PI 神经元似乎只传递了 SC 中发现的调制信号的一个子集：它们表现出眼跳抑制，即在眼跳时抑制活动，但没有清楚地显示出 SC 中观察到的视觉反应的注意力增强。其次，属于上升路径的 PI 神经元的方向选择性最小，但从 MT 接收输入的 PI 神经元的方向选择性显著更为突出。这一发现对之前关于 PI 向 MT 提供方向选择性信号的假设提出了质疑，反而表明 PI 从 MT 获得了选择性。该通路的识别及其传输的活动建立了第一个从脑干到皮质通过下丘的功能通路，并使其能够研究其对皮质视觉处理、感知和动作的贡献。
