About 5% of the retinal ganglion cells are “Magnocellular” ; these larger cells have relatively large receptive fields with transient responses that are relatively more sensitive to motion and contrast. Conversely, about 90% of the retinal ganglion cells are “parvocellular” and have smaller receptive fields with sustained responses that are relatively more sensitive to color, fine detail, and form. These streams remain segregated in the LGN (the M fibers synapse in bottom two layers [1 & 2] while the P fibers synapse in the top 4 layers [3-6]). Both reach V1 which preferentially sends M-cell information to the dorsal/where stream and P-cell information to the ventral/what stream.
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