Figure 3. Mice lacking Lrp4 in the CNS display defects in learning and memory.
(A) A schematic representation of the fear-conditioning paradigm. Lrp4−/−; Lrp4m mice exhibit a decrease in freezing behavior, compared to littermate control mice, when presented with an aversive conditioned stimulus (Lrp4−/−; Lrp4m, n = 12; littermate controls, n = 14). (B) A schematic representation of the passive avoidance paradigm. Lrp4−/−; Lrp4m mice were less hesitant to enter a dark chamber associated with an aversive stimulus (Lrp4−/−; Lrp4m, n = 13; littermate controls, n = 17). (C) Lrp4−/−; Lrp4m mice showed spatial learning deficits and reduced cognitive flexibility in the Morris water maze. Both control and Lrp4−/−; Lrp4m mice were able to locate the escape platform during the visible version of the water maze (Lrp4−/−; Lrp4m, n = 8; littermate controls, n = 9). (D) Lrp4−/−; Lrp4m and control mice displayed comparable swimming velocity during the Morris water maze. (E) Lrp4−/−; Lrp4m and control mice spent more time searching in the target quadrant region than other quadrants during the probe trial. (F) Lrp4−/−; Lrp4m and control mice crossed the platform site with similar frequency during the probe trial. (G) Lrp4−/−; Lrp4m mice spent less time in the new target quadrant during reversal training. See also Figure 4.