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. 2011 Dec 28;5:84. doi: 10.3389/fnbeh.2011.00084

Figure 3.

Figure 3

Ras-GRF1 KO mice exhibit a reconsolidation deficit. (A) Protocols for repeated familiarizations (top) and for memory reconsolidation test (bottom). Top: mice are introduced into the arena in the presence of two identical objects for one (single familiarization phase) or eight consecutive sessions of 5 min (multiple familiarization phase). After a delay of 48 h the test phase is performed. Bottom: mice are introduced into the arena in presence of two identical objects for eight consecutive sessions of 5 min each. Twenty-four hours later mice memory trace is reactivated by re-exposing the mice to the same two familiar objects. After a delay of 10 min or of 24 h the test phase is performed. (B) Discrimination index of Ras-GRF1 KO mice 48 h after a single familiarization session or after repeated familiarization sessions. Asterisk denotes significant difference between Ras-GRF1 KO mice (n = 16 for the repeated familiarization, n = 20 for the single familiarization) in the two conditions (Mann–Whitney p = 0.012). Repeated exposure to the stimuli is sufficient to compensate for the deficit of visual recognition memory of Ras-GRF1 KO mice. (C) Discrimination index of Ras-GRF1 KO and WT mice 48 h after repeated familiarization sessions and 24 h after memory reactivation. In wt, re-exposure of the animals to the stimuli did not interfere with recognition of the familiar stimulus 24 h later (control n = 20, reactivated n = 16; p = 0.43 Mann–Whitney). By contrast a single exposure to the familiar stimulus 24 h after its memorization makes the memory trace labile in Ras-GRF1 KO mice: 24 h after reactivation, discrimination index was significantly decreased with respect to that found without reactivation (control n = 15, reactivated n = 17; p = 0.026 Mann–Whitney). (D) Exploration time of novel and familiar object of Ras-GRF1 KO mice 24 h after reactivation: there is no preferential exploration of the novel object (time of exploration of new object, tN versus time exploration familiar object, tF, control p < 0.001; reactivated p = 0.212 paired t-test). Asterisks denote significant differences. (E) Discrimination index 10 min after reactivation; the deficit in Ras-GRF1 KO mice was not present 10 min after reactivation.