▁rod ▁cells , ▁which ▁provide ▁syn apt ic ▁input ▁onto ▁ip R GC s , ▁which ▁in ▁turn ▁relay ▁the ▁information ▁to ▁the ▁ol iv ary ▁pre te ct al ▁nucle us ▁in ▁the ▁mid bra in . ▁The ▁ne uro trans mit ter ▁involved ▁in ▁the ▁relay ▁of ▁information ▁to ▁the ▁mid bra in ▁from ▁the ▁ip R GC s ▁in ▁the ▁trans ient ▁PL R ▁is ▁gl ut am ate . ▁At ▁br ighter ▁light ▁intens ities ▁the ▁sust ained ▁PL R ▁occurs , ▁which ▁involves ▁both ▁phot otr ans du ction ▁of ▁the ▁rod ▁providing ▁input ▁to ▁the ▁ip R GC s ▁and ▁phot otr ans du ction ▁of ▁the ▁ip R GC s ▁themselves ▁via ▁mel an ops in . ▁Research ers ▁have ▁suggested ▁that ▁the ▁role ▁of ▁mel an ops in ▁in ▁the ▁sust ained ▁PL R ▁is ▁due ▁to ▁its ▁lack ▁of ▁adaptation ▁to ▁light ▁stim uli ▁in ▁contrast ▁to ▁rod ▁cells , ▁which ▁exhib it ▁adaptation . ▁The ▁sust ained ▁PL R ▁is ▁maintained ▁by ▁P AC AP ▁release ▁from ▁ip R GC s ▁in ▁a ▁p uls atile ▁manner . ▁ ▁Possible ▁role ▁in ▁conscious ▁sight ▁▁ ▁Exper iments ▁with ▁rod less , ▁con eless ▁humans ▁allowed ▁another ▁possible ▁role ▁for ▁the ▁re ceptor ▁to ▁be ▁studied . ▁In ▁ 2 0 0 7 , ▁a ▁new ▁role ▁was ▁found ▁for ▁the ▁phot ore cept ive ▁gang l ion ▁cell . ▁Za idi ▁and ▁colle agues ▁showed ▁that ▁in ▁humans ▁the ▁ret inal ▁gang l