Fig. 4

AD rats have a deficit in the retention of social memory but have no short- or long-term spatial memory deficits. Rats were i.c.v. injected with AD or non-AD control extracts (n = 12 per group) and tested for A social memory on Day 21 after the infusion. Data were analyzed using Student’s t-test to compare social recognition ratios (RRs) between groups and one sample t-test to compare each group to a chance value of 0.5. Data are presented as the means ± SEM. **p < 0.01 compared with control rats,  ++p < 0.01 compared to the hypothetical chance value of 0.5 (dashed line). B Control and AD rats started acquisition training in the MWM on Day 29 after the i.c.v. infusion, and C reference memory was tested 24 h and 7 days after the last training session. During the 3 days of acquisition training, the time spent in the target quadrant decreased, indicating spatial learning and memory formation in both groups. (C, left panel) Rats from both groups spent significantly less time in the target quadrant and (C, right panel) made fewer entries into the platform zone during the second probe trial (Day 7) compared to the first probe trial (24 h). Data were analyzed using two-way-ANOVA, *p < 0.05. D The Y-maze test, which was performed on Day 39 postinjection, revealed no difference in either the number of entries (D, left panel) or the percentage of alternations (D, center panel) between the AD and control groups. (D, right panel) The AD rats spent a significantly lower percentage of time spent in the central zone of the Y-maze than control rats. Data were analyzed using Student’s t-test, *p < 0.05. A–D n = 12 rats per group