Emergence of light responses

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Journal Article

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Retinal Development




© Cambridge University Press 2006 and 2009. Introduction Although the newborn retina is highly active, with spontaneous waves propagating across the amacrine and the ganglion cell layers every few minutes (see Chapter 13), at that time it is not yet possible to elicit light responses in retinal ganglion cells (RGCs). This lack of responsiveness to light is due to the immaturity of the vertical synaptic pathway between photoreceptors and RGCs provided by bipolar cells (BCs), despite the fact that lateral connections in the inner retina are already well established (see Chapter 13). Moreover, rod and cone opsins are not yet functional at birth. In mouse for example, ultraviolet cone opsin does not appear until postnatal day (P)1, rod opsin until P5 and green cone opsin until P7 (Tarttelin et al., 2003). Hence, RGCs become visually responsive only shortly before eye opening (around P10 in rabbit; Masland, 1977; Dacheux and Miller, 1981a, b; P7 to P10 in cat; Tootle, 1993; P12 in mouse; Sekaran et al., 2005). Humans and other primates, on the other hand, are born with their eyes open and although primate vision is poor at birth a newborn human infant is capable of tracking visual stimuli (Teller, 1997). This chapter reviews the earliest light responses that can be detected in the developing retina. New studies show that the newborn retina is actually not insensitive to light and this will be considered in the first part of the chapter.

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