FIGURE 5.

(A) Timeline of infusions and mnemonic discrimination tests administered in Experiment 1. All rats (n = 10) received a vehicle (veh) and muscimol (mus) infusion in each of three tests blocks. Order of veh and mus infusions in each test block was randomized across rats with a Latin square design, therefore this timeline shows one example permutation of infusion order. Tests took place every 3 days, with 2 wash-out days on which rats remained in their home cages and did not complete any behavioral training or testing. Infusions were administered 30 min prior to the beginning of each test. (B,C) Performance (% correct trials) on mnemonic discrimination tests in Experiment 1 plotted by trial type, with each of the 4 lure objects sharing 0, 50, 70, or 90% visible front-facing features (target-lure overlap). Test performance on days with vehicle infusions (veh) designated by open circles, and on days with muscimol infusions (mus) by filled circles. (B) Mean ± SEM performance on mnemonic discrimination tests collapsed across 3 test blocks, to a total of 30 trials with each lure object under each infusion condition. Rats made fewer correct responses on trials with LEGO lures (50–90% target-lure overlap), relative to the standard object lure [0% overlap; main effect lure: F_(3,27) = 44.1, p < 0.001; simple contrasts: p’s < 0.01]. (C) Mean ± SEM performance plotted for each of the 3 test blocks (10 trials/lure object/infusion condition). Muscimol impaired discrimination when lure objects were novel, in block 1, across all lures [main effect infusion: F_(1,7) = 16.7, p < 0.005]. By block 2, muscimol impaired performance only on the 70% target-lure overlap problem [infusion × lure: F_(3,27) = 2.95, p < 0.05]. No difference in performance between infusion conditions was observed in block 3.