Callosal contribution to ocular dominance in rat primary visual cortex
Callosal contribution to ocular dominance in rat primary visual cortex
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DOI：
10.1111/j.1460-9568.2010.07363.x
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发表时间：
2010-10-01
影响因子：
3.4
通讯作者：
Caleo, Matteo
中科院分区：
文献类型：
--
作者：
Cerri, Chiara;Restani, Laura;Caleo, Matteo
单眼皮缝合引发的眼优势可塑性是研究经验依赖性神经连通性变化的经典范例。最近，啮齿动物已经成为研究OD可塑性的最流行的模型。因此，确定OD如何在啮齿动物的初级视觉皮层中决定是很重要的。特别是，皮层细胞通过胼胝体轴突接受来自对侧半球的大量输入，但这些连接在控制眼睛偏好中的作用仍然存在争议。在这里，我们研究了胼胝体连接在幼稚的年轻大鼠视觉皮层的双眼视功能中的作用。我们通过立体定向河豚毒素（TTX）注射，记录了记录部位同侧外侧膝状核在急性沉默前后刺激每只眼睛所引起的皮质反应。该方案使我们能够分离通过胼胝体传递的视觉反应。通过视觉诱发电位（VEP）和单单元记录评估皮质双眼视功能。我们发现传入神经皮质输入的急性沉默导致对侧与同侧（C/I） VEP比率的显著降低，并且皮层细胞的OD分布明显向同侧眼转移。对每只眼睛的绝对强度分析表明，TTX后对侧眼睛的反应明显减少，而同侧眼睛的反应减少，但保持更明显的输入。我们得出结论，胼胝体连接主要通过携带同侧眼的视觉输入来促进正常OD。这些数据对于解释视觉经验改变后的外径可塑性具有重要意义。
Ocular dominance (OD) plasticity triggered by monocular eyelid suture is a classic paradigm for studying experience-dependent changes in neural connectivity. Recently, rodents have become the most popular model for studies of OD plasticity. It is therefore important to determine how OD is determined in the rodent primary visual cortex. In particular, cortical cells receive considerable inputs from the contralateral hemisphere via callosal axons, but the role of these connections in controlling eye preference remains controversial. Here we have examined the role of callosal connections in binocularity of the visual cortex in naive young rats. We recorded cortical responses evoked by stimulation of each eye before and after acute silencing, via stereotaxic tetrodotoxin (TTX) injection, of the lateral geniculate nucleus ipsilateral to the recording site. This protocol allowed us to isolate visual responses transmitted via the corpus callosum. Cortical binocularity was assessed by visual evoked potential (VEP) and single-unit recordings. We found that acute silencing of afferent geniculocortical input produced a very significant reduction in the contralateral-to-ipsilateral (C/I) VEP ratio, and a marked shift towards the ipsilateral eye in the OD distribution of cortical cells. Analysis of absolute strength of each eye indicated a dramatic decrease in contralateral eye responses following TTX, while those of the ipsilateral eye were reduced but maintained a more evident input. We conclude that callosal connections contribute to normal OD mainly by carrying visual input from the ipsilateral eye. These data have important implications for the interpretation of OD plasticity following alterations of visual experience.