Recognition memory and learning in PLB1 mice.

A: Social recognition. Time (in seconds) spent with an unfamiliar stranger mouse (S1) and the corresponding empty compartment (E) at 5 and 12±1 months of age. During sociability (left), all groups spent significantly more time in the vicinity of the unfamiliar mouse compared to the empty holder. During the social memory phase (right), PLB1_WT mice discriminated between the now more familiar first stranger (S1*) and a novel, unfamiliar stranger (S2) in both age groups. PLB1_Triple only discriminated between the conspecifics at 5 months. Data are represented as means+SEM; n.s.: not significant; *: P<0.05; **:P<0.01; ***: P<0.001, arena and representative exploration patterns are also depicted. B: Object recognition and spatial novelty. Time (in %+SEM) spent with a novel object (left) or relocated object (right) in PLB1_WT and PLB1_Triple mice at 8 and 12±1 months. PLB1_Triple performed worse than PLB1_WT in both age groups during object recognition and did not discriminate between novel and familiar object at 12 months of age. At this age, recognition of spatial novelty was also affected. Significances are indicated between groups (*), a comparison with chance level is also given ($:P<0.05; $$: P<0.01; $$$: P<0.001). Examples path trajectories are illustrated on the right. C: Water maze learning. Mean daily path length (+ or − SEM) to reach a visible (V) platform, followed by spatial training to a submerged platform (days 1–4). At 5 and 12 months, PLB1_Triple mice were able to locate the visible platform, but were significantly impaired at 12 (but not 5) months in the hidden platform task compared to PLB1_WT (P<0.05). Arena set up with representative exploration patterns for day 1–4 (swim path) are depicted.