探討自主感光視神經細胞是否影響對比敏感性

Abstract

在視網膜中，視神經節細胞負責彙整感光細胞傳遞下來的訊號並將其傳遞至大腦中的視覺皮層形成視覺。有一種特殊的視神經節細胞可以感光，叫自主感光視神經細胞 (intrinsically photosensitive retinal ganglion cells)。雖然一開始自主視感光神經細胞僅被發現具有非成像相關之功能，像是調節生理時鐘與瞳孔反射等，越來越多證據指出自主感光視神經細胞也可以調控視覺成像。但是其中的機制仍然不清楚。在此篇研究中，我們利用小鼠作為模式動物去探討自主感光視神經細胞是否具有視覺成像的功能。藉由兩選項強迫選擇法(two-alternative forced choices)，我們發現在小鼠中剃除M1自主感光視神經細胞可能影響視覺成像。在小鼠中剃除M1自主感光視神經細胞使其需要更長的時間學習兩選項強迫選擇法。除此之外，M1自主感光視神經細胞剃除小鼠中也擁有與野生型小鼠相同的視覺敏銳度(visual acuity)與對比敏感性(contrast sensitivity)。我們研究指出兩選項強迫選擇法可以被利用於測量小鼠的視覺功能。

In retina, the retinal ganglion cell is responsible for integrating the signals form the photoreceptor, rod and cone, and sending the signals to the visual cortex to form the vision. There is one special type of retinal ganglion cell expressing photopigment, melanopsin, can detect the light called intrinsically photosensitive retinal ganglion cells (ipRGCs). Although ipRGCs were found only having non-image-forming function at first, such as circadian regulation and pupil light reflex, there are more and more evidences indicating that ipRGCs can modulate image-forming function. However, the mechanism remains unclear. Here, we use mice as the animal model to investigate whether the ipRGCs have the function in image-forming by using the two-alternative forced choices (2AFC) method. We found that it take more days for M1 eliminating mice to learn the task compare to the WT. In addition, M1 eliminating mice have similar spatial frequency threshold and contrast sensitivity function compared to WT. Our result show that 2AFC could be used to evaluate pattern vision in mice