Quantification of cFOS expression within retinorecipient regions across Zeitgeber Time. The total number of cFOS+ cells was compared across 12:12 LD conditions for grass rats (left column, black bars) and SD rats (right, gray bars) in several visual structures. In the grass rats, the OPN and IGL no longer express significant daily rhythms, however both the LHb and MHb have daily rhythms under LD conditions. In contrast, SD rats exhibited significant circadian rhythms of cFOS expression within the dLGN and IGL. Different letters indicate significance with p<0.05.