how do the LGN cell layers receive retinal output from different ganglion cells?
The right LGN receives information from the left visual field, and the left LGN receives info. from the right visual field.
At LGN, info from the two eyes is kept separate. In each LGN, the info from the temporal portion of the retina in the eye that is ipsilateral (same side) to the LGN is sent to layers 2,3, and 5 of the LGN. Meanwhile, the info from the nasal portion of the retina in the eye that is contralateral (opposite side) to the LGN is sent to layers 1,4, and 6.