Incidental learning (IL) can be studied using sensory preconditioning, a higher-order memory process. Incidental associations between low-salience stimuli (e.g. odors, tastes, lights or tones) happen during a preconditioning phase that is followed by classical conditioning of one of these stimuli with an aversive or appetitive unconditioned reinforcer. As a result, subjects present a response to the directly conditioned stimulus but also a mediated response to the preconditioned stimulus never explicitly reinforced, implying initial IL. We performed three different protocols to study IL using different sensory modalities, either odor and taste (OT) or light and tone (LT), and with both aversive (OT and AvLT) and appetitive (ApLT) values for the unconditioned reinforcer. Our previous work unveiled that IL requires type-1 cannabinoid receptor (CB1R) on hippocampal GABAergic interneurons, but the exact nature of the neurons involved has not been investigated so far. We showed that mice lacking CB1R specifically in neurons bearing type-1 dopaminergic receptor (D1R) are impaired in mediated, but not direct, responses in aversive protocols (OT and AvLT). We are currently establishing whether the same population of CB1R- and D1R-positive neurons underlie IL in appetitive paradigm (ApLT). Moreover, we will characterize whether hippocampal neurons are specifically involved by selective deletion and re-expression of CB1R in D1R hippocampal neurons. Finally we will determine how dopamine and endocannabinoid transmissions are modulated in the hippocampus during IL using selective receptor sensors (GRABDA and GRABeCB2.0) combined with fiber photometry.