Selective Activation of the Deep Layers of the Human Primary Visual Cortex by Top-Down Feedback
Selective Activation of the Deep Layers of the Human Primary Visual Cortex by Top-Down Feedback
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DOI：
10.1016/j.cub.2015.12.038
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发表时间：
2016-02-08
期刊：
影响因子：
9.2
通讯作者：
de lange, Floris P.
中科院分区：
文献类型：
--
作者：
Kok, Peter;Bains, Lauren J.;de lange, Floris P.
除了自下而上的输入，视觉皮层还接收来自其他皮层区域的大量反馈[1 - 3]。在没有自下而上输入的情况下，早期视觉神经元被反馈激活的一个令人信服的例子发生在著名的卡尼萨错觉期间，在这种错觉中，即使在图像中没有自下而上的视觉证据的区域，也能感知到一个三角形。这种错觉增加了初级视觉皮层中感受野位于错觉轮廓上的神经元的放电活动[4]。在每个皮层区域内，反馈信号在很大程度上与前馈信号是分离的，前馈信号到达中间层，而自上而下的反馈避开中间层，主要作用于深层和浅层[1, 2, 5, 6]。因此，在错觉形状感知过程中，V1中由反馈介导的活动增加应该导致一种特定的层状活动模式，这种模式不同于由自下而上刺激引发的活动。在这里，我们使用高场（7T）功能磁共振成像，通过探测人类V1在不同皮层深度对错觉图形的皮层反应，对这一假设进行了实证检验[7 - 14]。我们发现，自下而上的刺激激活了所有皮层层，而错觉图形诱导的反馈活动导致了V1深层的选择性激活。这些结果展示了在人类中以层状特异性无创记录神经活动的潜力，并阐明了自上而下的信号在知觉加工过程中的作用。
In addition to bottom-up input, the visual cortex receives large amounts of feedback from other cortical areas [1-3]. One compelling example of feedback activation of early visual neurons in the absence of bottom-up input occurs during the famous Kanizsa illusion, where a triangular shape is perceived, even in regions of the image where there is no bottom-up visual evidence for it. This illusion increases the firing activity of neurons in the primary visual cortex with a receptive field on the illusory contour [4]. Feedback signals are largely segregated from feedforward signals within each cortical area, with feedforward signals arriving in the middle layer, while top-down feedback avoids the middle layers and predominantly targets deep and superficial layers [1, 2, 5, 6]. Therefore, the feedback-mediated activity increase in V1 during the perception of illusory shapes should lead to a specific laminar activity profile that is distinct from the activity elicited by bottom-up stimulation. Here, we used fMRI at high field (7 T) to empirically test this hypothesis, by probing the cortical response to illusory figures in human V1 at different cortical depths [7-14]. We found that, whereas bottom-up stimulation activated all cortical layers, feedback activity induced by illusory figures led to a selective activation of the deep layers of V1. These results demonstrate the potential for non-invasive recordings of neural activity with laminar specificity in humans and elucidate the role of top-down signals during perceptual processing.