兔子視網膜中方向選擇性節細胞的反應與移動背景之關係

Motion Background Context Modulates the Response of Direction Selective Ganglion Cells in the Rabbit Retina

呂紹瑋(Shao-Wei Lu)

指導教授 ： 焦傳金

國立清華大學/生命科學院/分子醫學研究所/碩士(2007年)

https://doi.org/10.6843/NTHU.2007.00633

摘要

一個傳統的視網膜節細胞感受域具有中央與周圍區域互相拮抗的機制，這樣的特性可以增強視網膜的功能，以強化物體邊緣的偵測能力。先前的研究已發現數種視網膜節細胞能將一個或是多個移動中的物體從移動中的背景中區分出來。在兔子的視網膜中有一種特別的節細胞是用來辨認物體的運動方向（方向選擇性節細胞）。本篇研究的目的是想探究在不同的移動背景下，方向選擇性節細胞的反應是否會被影響。四個主要的參數用來調整背景的狀態包括：空間的覆蓋率、背景分佈的區域、背景空間裡的尺寸關係以及移動背景的同調性。結果顯示，不同的移動背景狀態會對方向選擇性節細胞有顯著的調控作用。特別是依據它們對移動背景的反應方式可以將方向選擇性節細胞進一步分成三個類別。除了兩類具有周圍抑制性反應的節細胞外，第三類的細胞會在移動背景的條件下出現周圍興奮性的反應。我認為這第三類的對周圍移動產生興奮性反應的細胞可能參與了一個在動物運動過程中的視網膜預警系統。比如說，此類細胞的訊號可以提供奔跑過程中的兔子偵測獵食者的出現。因此，視網膜所做的視覺訊息處理可能遠比我們所想的還要精細，包括方向性的感測會受到移動背景結構的顯著影響。

關鍵字

方向選擇性節細胞 ； 移動背景抑制作用 ； 移動背景興奮作用 ； 移動背景結構

並列摘要

A classical receptive field of retinal ganglion cells has a center-surround antagonistic property. This characteristic can enhance retina’s functions to detect object’s edge. Previous studies have shown that some ganglion cells can segregate moving objects from moving background. In the rabbit retina, direction selective ganglion cells (DSGCs) are known for their ability to differentiate object’s motion directions in the visual field. In this study, the goal is to investigate how the context of moving background affects the DSGC’s response. Four major parameters of background contexts were used, including spatial coverage, immediate surround extent, spatial scale, and motion coherence. The results reveal that DSGCs’ responses are strongly modulated by various motion background contexts. Specifically, three types of DSGCs can be grouped according to their tuning curves. Among them, two types of DSGCs showed a characteristic motion surround inhibition, but the other one exhibited some surround excitation under certain moving background conditions. I proposed that these excitatory surround DSGCs may be involved in a warning mechanism for detecting a moving object during self-motion, e.g., signaling the presence of a predator while running. The result indicates that the retina can do much more sophisticated tasks than we thought, including detection of direction selectivity under various background contexts.

並列關鍵字

direction selective ganglion cell ； motion surround inhibition ； motion surround excitation ； motion background context

參考文獻

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