The dentate gyrus is positioned at the entrance of the hippocampus, receiving polysensory information from the entorhinal cortex, and transferring it into the hippocampus proper. Due to its anatomical and physiological properties it is able to generate sparse patterns of activity from rich entorhinal cortex inputs. We are interested in how the dentate gyrus and down-stream regions are recruited during memory formation. To this end, we are using learning paradigms that are dentate-gyrus dependent. These include both spatial memory paradigms requiring pattern separation, as well as forms of memory that require spatial or non-spatial association of aversive and reward stimuli.