Motion area V5/MT+ response to global motion in the absence of V1 resembles early visual cortex.
Motion area V5/MT+ response to global motion in the absence of V1 resembles early visual cortex.
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DOI：
10.1093/brain/awu328
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发表时间：
2015-01
期刊：
影响因子：
--
通讯作者：
Bridge H
中科院分区：
文献类型：
--
作者：
Ajina S;Kennard C;Rees G;Bridge H
关于非V1输入如何影响运动区域V5/MT+，人们知之甚少。Ajina等人揭示，V1损伤后，V5/MT+活动类似于早期视皮层的活动，可能由类似的皮层下输入驱动。虽然这些输入通常被V1连接所掩盖，但承认它们的贡献可能会改善神经元模型。运动区V5/MT+显示出各种特征性的视觉反应，通常与感知有关，这在很大程度上受到其与初级视觉皮层（V1）的丰富连接的影响。这个人类运动区域也接收来自其他视觉区域的大量输入，包括直接的皮层下连接和与对侧半球的胼胝体连接。目前对V5/MT+的这些替代输入以及它们如何驱动和影响其活动知之甚少。使用功能性磁共振成像，在7名成年期单侧V1损伤的患者和一组年龄匹配的健康对照组中测量了人类V5/MT+对增加相干运动比例的反应。当V1受损时，对增加相干性的典型V5/MT+反应丧失。相反，患者的V5/MT+显示出与健康对照受试者V1中的相干性相关活性相似的负趋势。这种向早期视皮层更典型的反应模式的转变表明，在V1缺失的情况下，V5/MT+活动可能受到类似的直接皮层下输入的影响。这可能反映了完整的残留通路，而不是连接的变化，并对盲视功能具有重要意义。它还证实了预测，V1是关键参与正常的V5/MT+全球运动处理，与V1输入到V5/MT+的收敛模型一致。从历史上看，大多数对皮层视觉反应建模的尝试都没有考虑可能绕过纹状体皮层的直接皮层下输入的贡献，例如V5/MT+的输入。我们已经表明，这些非纹状体通路驱动的信号变化可以测量，并建议模型的完整的视觉系统可能会受益于考虑他们的贡献。
Little is known about how non-V1 inputs influence motion area V5/MT+. Ajina et al. reveal that after V1 damage, V5/MT+ activity resembles that of early visual cortex, perhaps driven by similar subcortical inputs. While these inputs are normally overshadowed by V1 connections, acknowledging their contribution may improve neuronal models. Motion area V5/MT+ shows a variety of characteristic visual responses, often linked to perception, which are heavily influenced by its rich connectivity with the primary visual cortex (V1). This human motion area also receives a number of inputs from other visual regions, including direct subcortical connections and callosal connections with the contralateral hemisphere. Little is currently known about such alternative inputs to V5/MT+ and how they may drive and influence its activity. Using functional magnetic resonance imaging, the response of human V5/MT+ to increasing the proportion of coherent motion was measured in seven patients with unilateral V1 damage acquired during adulthood, and a group of healthy age-matched controls. When V1 was damaged, the typical V5/MT+ response to increasing coherence was lost. Rather, V5/MT+ in patients showed a negative trend with coherence that was similar to coherence-related activity in V1 of healthy control subjects. This shift to a response-pattern more typical of early visual cortex suggests that in the absence of V1, V5/MT+ activity may be shaped by similar direct subcortical input. This is likely to reflect intact residual pathways rather than a change in connectivity, and has important implications for blindsight function. It also confirms predictions that V1 is critically involved in normal V5/MT+ global motion processing, consistent with a convergent model of V1 input to V5/MT+. Historically, most attempts to model cortical visual responses do not consider the contribution of direct subcortical inputs that may bypass striate cortex, such as input to V5/MT+. We have shown that the signal change driven by these non-striate pathways can be measured, and suggest that models of the intact visual system may benefit from considering their contribution.
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