CIRCUITRY OF THE MIDGET AND PARASOL RECEPTIVE FIELD

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 这个项目的目标是确定如何在神经节细胞的水平上建立感受野周围，以及周围如何通过识别对周围的视锥输入来促进颜色编码。突触前假说认为，视锥双极中心-周围组织的形成是视锥突触性的关键所在。我们第一次在哺乳动物视网膜中发现，锥双极细胞具有与神经节细胞相媲美的强大的中心-周围组织。然后，我们进行了一系列实验，试图选择性地阻断神经节细胞周围。我们发现，在parasol细胞，无论是钴或缝隙连接阻断剂，甘珀酸，选择性地减少周围的拮抗作用。我们现在正在使用这些药物来评估感受野周围的贡献，在一些神经节细胞类的颜色一致性。 在第二个系列的实验中，我们开发了一种新的刺激协议来测量的强度和符号的L，M和S-锥输入的感受野周围的侏儒和阳伞神经节细胞类型。 具体目标是评估在从外部到内部视网膜回路的传输期间如何改变视锥信号加权。我们发现，从水平双极细胞水平到神经节细胞周围没有增益变化，并得出结论，锥体类型特异性突触增益变化不是产生颜色对手信号的可能机制。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The goal of this project is determine how the receptive field surround is established at the level of the ganglion cell and how the surround contributes to color-coding by identifying the cone inputs to the surround. The presynaptic hypothesis predicts that the creation of the cone bipolar center-surround organization is the critical locus for cone opponency. We showed for the first time in a mammalian retina that cone bipolar cells have robust center-surround organization comparable to their ganglion cell counterparts. We then undertook a series of experiments to attempt to selectively block ganglion cell surrounds. We found, in parasol cells, that either cobalt or the gap-junction blocker, carbenoxolone, selectively reduces surround antagonism. We are now using these drugs to assess the receptive field surround contribution to color-opponency in a number of ganglion cell classes. In a second series of experiments, we developed a new stimulus protocol to measure the strength and sign of L, M and S-cone inputs to the receptive field surrounds of midget and parasol ganglion cell types. The specific goal was to assess how cone signal weighting may be altered during transmission from outer to inner retinal circuitry. We showed that there are no gain changes from the horizontal-bipolar cell level to the ganglion cell surround and concluded that cone type-specific changes in synaptic gain are not a likely mechanism for generating color-opponent signals.