A transgene with the synthetic CAG promoter driving expression of a chlamyopsin 4 (COP4, or channelrhodopsin 2, ChR2) EGFP fusion protein (COP4/EGFP) following cre mediated removal a floxed transcripitonal stop signal (loxp sites flanking 3 copies of a polyadenylation signal was targeted to the Gt(ROSA)26Sor locus. (J:194305)