To allow for the mechanistic separation of olfactory learning, discrimination, and memory, we exploited a well-known phenomenon of transgenes, which concerns heterogeneous expression among different founder lines and even among genetically identical individuals of a given line. Although such “mosaic” expression is usually undesired, here we took advantage of it by ablating GluR-B via gene-targeted, floxed GluR-B alleles with the help of a transgenic mouse line with variegated Cre expression in forebrain. By correlating GluR-B levels in olfaction-related brain regions with quantitative behavioral data, we investigated the dependence on GluR-B of olfactory discrimination and memory. Moreover, to delineate the brain areas involved in these distinctive olfactory processes we used transgenic “rescue” of GluR-B ablation, specifically in piriform cortex and hippocampus.