Memory acquisition and retrieval upregulate the expression of similar genes. A. Btg2, Sox18 and Sik1 are regulated at both FC30' (dark grey) and RT30' (light gray). B. Selective upregulation of Per1 isoforms at FC30' and RT30'. Microarray and qPCR samples are from independent cohorts of animals (n = 9, n = 8). qPCR values represent average fold change relative to controls (CC30') after normalization against Gapdh levels. Microarray experiment results are labeled (M). Fos is included as positive control. Statistical significance is shown as either fer (microarrays) or p-values (qPCR), <0.01(**) or <0.1 (*).