Light-induced FOS expression in the SCN of CBA/J and CBA/N mice. A. There are greater numbers of FOS-positive cells in the SCN in response to a 1hr light pulse is greater in CBA/J (dark grey) than CBA/N mice (white). Light grey bars show that FOS expression is significantly less in animals kept in DD and does not differ between strains (light grey bars). * = p = 8.9 × 10-5, t8 = 7.2.