Segregated Pathways Carrying Frontally Derived Top-Down Signals to Visual Areas MT and V4 in Macaques
Segregated Pathways Carrying Frontally Derived Top-Down Signals to Visual Areas MT and V4 in Macaques
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DOI：
10.1523/jneurosci.6295-11.2012
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发表时间：
2012-05-16
影响因子：
5.3
通讯作者：
Takada, Masahiko
中科院分区：
文献类型：
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作者：
Ninomiya, Taihei;Sawamura, Hiromasa;Takada, Masahiko
自下而上的视觉信息处理受到自上而下信号的强烈影响，至少部分信号被认为是从额叶皮质通过额叶眼场(FEF)和外侧顶内区(LIP)传递的。在这里，我们研究了猕猴从额叶皮质到背侧视流的中颞区(MT)和腹侧视流的视区4(V4)的多突触通路的构筑。在第一系列实验中，将逆行跨突触示踪剂狂犬病病毒注射到MT或V4。狂犬病注射后3天，46区腹侧(46V区)出现二级(双突触连接)神经元标记，FEF和LIP出现一级(单突触连接)神经元标记。在注射MT的情况下，在补充眼野(SEF)也观察到二级神经元。在接下来的一系列实验中，将两种荧光染料坚牢蓝和二氨基黄分别注入MT和V4，以检查额叶输入是由不同的神经元群还是共同的神经元群介导的。在FEF和LIP中几乎没有观察到双标记神经元，这表明单独的神经元群介导了MT和V4的额叶输入。这些结果表明，V4的多突触额叶输入主要来自46V区，而V4的输入不仅来自46V区，而且还通过FEF和LIP神经元。来自额叶皮质的分离通路可能将功能不同的自上而下的信号携带到每一条视觉流中。
The bottom-up processing of visual information is strongly influenced by top-down signals, at least part of which is thought to be conveyed from the frontal cortex through the frontal eye field (FEF) and the lateral intraparietal area (LIP). Here we investigated the architecture of multisynaptic pathways from the frontal cortex to the middle temporal area (MT) of the dorsal visual stream and visual area 4 (V4) of the ventral visual stream in macaques. In the first series of experiments, the retrograde trans-synaptic tracer, rabies virus, was injected into MT or V4. Three days after rabies injections, the second-order (disynaptically connected) neuron labeling appeared in the ventral part of area 46 (area 46v), along with the first-order (monosynaptically connected) neuron labeling in FEF and LIP. In the MT-injection case, second-order neurons were also observed in the supplementary eye field (SEF). In the next series of experiments, double injections of two fluorescent dyes, fast blue and diamidino yellow, were made into MT and V4 to examine whether the frontal inputs are mediated by distinct or common neuronal populations. Virtually no double-labeled neurons were observed in FEF or LIP, indicating that separate neuronal populations mediate the frontal inputs to MT and V4. The present results define that the multisynaptic frontal input to V4 arises primarily from area 46v, whereas the input to V4 arises from not only area 46v but also SEF, through distinct FEF and LIP neurons. Segregated pathways from the frontal cortex possibly carry the functionally diverse top-down signals to each visual stream.