Sensing light signals not only provide the image vision for us, but also regulates many important physiological functions such as circadian-rhythm photoentrainment, mode,sleep, pupillary light reflex, etc.-functions referred to collectively as "non-image vision".A small subset of retinal ganglion cells (ipRGCs), which directly project to the brain regions for non-image vision, can sense light by themselves, i.e., intrinsically photosensitive,by virtue of their expression of melanopsin, a recently discovered visual pigment.We found that ipRGCs employ phosphatidylinositol signal pathway, including PLC-b4 and TRPC6,7 channels, to translate light signal into photocurrents, which closely resembles the phototransduction of invertebrates, such as drosophila.To detect ambient light level for non-image vision functions, ipRGCs have very slow but tightly controlled light-response kinetics.