(A) Schematic of experimental design showing photoexcitation of the IL→BLA pathway during CS presentation during partial (10-trial) extinction training. (B) Relative to YFP controls photoexcitation of IL→BLA pathway decreased freezing on the first trial-block of extinction training and on subsequent (light-free) retrieval in mice expressing a high-titer viral construct, decreased freezing on retrieval only in medium titer expressing mice, and was without effect at any stage of testing in low titer expressing mice. (C) Freezing during first trial-block of extinction training inversely correlated with fluorescence intensity in the BA. Data are means ± SEM. eYFP n=6, high titer n=5, medium n=5, low n=8. *P<0.05 versus YFP.