Figure 4.

A. First choice preference of novel objects. The line plot graph shows the scores during the 13 sessions (left). The bar chart represents mean scores over the first set of six sessions (1^st block) and the subsequent set of seven sessions (2^nd block). Data are shown as mean ± SEM. A score significantly above 50 (one-sample t test) indicates first choice preference for the novel object. * p < 0.05, ** p < 0.01, *** p 0< 0.001 (right). B. Discrimination ratio D2 = [(novel_(sec) -familiar_(sec)) / total exploration_(sec)] for final session. The D2 score is re-calculated after each trial as data from successive trials are accumulated. A score of zero reflects a failure to discriminate novel from familiar. Data shown are mean ± SEM. Group differences: *** p < 0.001.