<P> Most mature ganglion cells are able to fire action potentials at a high frequency because of their expression of K 3 potassium channels . </P> <P> Below is a very quick summary . For a reference source, please consult "Connecting the Retina to the Brain" by Erskine et al. and "Retinal Axon Growth at the Optic Chiasm" by Petros TJ et al . Most information highlighted below comes from these two excellent reviews . </P> <P> Retinal ganglion cells (RGCs) are born between embryonic day 11 (E11) and post-natals (PN) day zero (PN0) in the mouse and between week 5 and week 18 in utero in human development . In mammals, RGCs are typically added at the beginning in the dorsal - central aspect of the optic cup, which is located in the center of the eye . Then, RC growth will sweep out ventrally and peripherally from there, in a wave - like pattern . This process depends on a host of factors, ranging from signaling factors like FGF3 and FGF8 to proper inhibition of the Notch signaling pathway . Most importantly, the bHLH (basic Helix - Loop - Helix) - domain containing transcription factor Atoh7 and its downstream effectors, such as Brn3b and Isl - 1, work to promote RGC survival and differentiation . The "differentiation wave" that drives RGC development across the retina is also regulated in particular of the bHLH factors Neurog2 and Ascl1 and FGF / Shh signaling, deriving from the periphery . </P> <P> Early progenitor RGCs will typically extend processes connecting to the inner and outer limiting membranes of the retina with the outer layer adjacent to the retinal pigment epithelium (RPE) and inner adjacent to the future vitreous humor . The cell soma will pull towards the RPE, undergo terminal differentiation, and then migrate backwards towards the inner limiting membrane . It will then extend an axon in the retinal ganglion cell layer . This process is likely mediated by Slit - Robo signaling, which controls the retraction of the apical process of the RGC . </P>

Which of the following is not a type of retinal neuron