<P> When RGCs approach the optic chiasm, the point at which the two optic nerves meet, at the ventral diencephalon around E10 - E11 in the mouse, they have to make the decision to decussate to the contralateral optic tract or remain in the ipsilateral optic tract . In the mouse, about 5% of RGCs, mostly those coming from the ventral - temporal crescent (VTc) region of the retina, will remain ipsilateral, while the remaining 95% of RGCs will cross . This is largely controlled by the degree of binocular overlap between the two fields of sight in both eyes . Mice do not have a significant overlap, whereas, humans, who do, will have about 50% of RGCs cross and 50% will remain ipsilateral . </P> <P> Once RGCs reach the chiasm, the glial cells supporting them will change from an intrafascicular to radial morphology . A group of diencephalic cells that express the cell surface antigen stage - specific embryonic antigen (SSEA) - 1 and CD44 will form an inverted V - shape . They will establish the posterior aspect of the optic chiasm border . Additionally, Slit signaling is important here: Heparin sulfate proteoglycans (HSPGs), proteins in the ECM, will anchor the Slit morphogen at specific points in the posterior chiasm border . RGCs will begin to express Robo, the receptor for Slit, at this point thus facilitating the repulsion . </P> <P> RGC axons traveling to the contralateral optic tract need to cross . Shh plays a role in this . It is expressed along the midline in the ventral diencephalon, providing a repulsive cue to prevent RGCs from crossing the midline ectopically . However, a hole is generated in this gradient, thus allowing RGCs to decussate (research is still actively done to understand the mechanism behind this isolated obliteration). </P> <P> Molecules mediating attraction include NrCAM, which is expressed by growing RGCs and the midline glia and acts along with Sema6D, mediated via the Plexin - A1 receptor . VEGF - A is released from the midline directs RGCs to take a contralateral path, mediated by the Neuropilin - 1 (NRP1) receptor . cAMP seems to be very important in regulating the production of NRP1 protein, thus regulating the growth cones response to the VEGF - A gradient in the chiasm . </P>

Where do the optic nerve ganglion cells send most information