Fig. 2
Medial entorhinal cortex (MEC) is selectively involved in encoding where information. a A horizontal tissue section shows bilateral expression of Gi-DREADD associated mCherry in the MEC (asterisks) and its medial perforant path (MPP) projection to the dentate gyrus (DG) molecular layer (bar = 400 μm). b Plot of MPP fEPSP slopes shows that CNO infusion caused a rapid reduction in MPP synaptic responses in slices from MEC-DREADD mice but not in slices from naïve control (CTRL) mice (mean ± SEM). Representative MPP fEPSP traces recorded in the absence (black) and presence (blue) of CNO in slices from control and Gi-DREADD mice. Scale bars: y = 1 mV, x = 5 ms. c Treatment of MEC-DREADD mice with CNO but not vehicle (VEH) prior to training significantly blocked Where task learning without influencing performance in What or When tests (within group comparisons: *p < 0.05; **p < 0.01; ***p = 0.0009; N.S. p > 0.05, paired t-tests; CNO groups: What n = 7; Where n = 8; When n = 8; between group VEH versus CNO comparison *p < 0.05, unpaired t-test). d Transfected mice treated with VEH or CNO both spent more time exploring the novel than the familiar cue in the 2-odor task (*p = 0.022 for VEH, *p = 0.022 for CNO, paired t-test). e Protocol for testing what memory in the context used to assess where acquisition. f MEC-DREADD animals given CNO treatment prior to odor exposure showed a marked preference for a novel cue (what) in subsequent retention tests (VEH n = 8, CNO n = 9, *p = 0.015, ***p = 0.0006, paired t-tests)
