Fig. 5

Effect of FMT from adult and old mice on spatial learning and memory. Barnes maze test (Fig. 3a–c): mice were trained to find the cage for 4 consecutive days (twice daily; 2 trials). The average primary latency (Fig. 3a) was significantly higher for adult recipients of microbiota from aged donors (FMT-aged) than the other control groups either left untreated or colonized with microbiota from adult, age-matched donors (FMT-adult). Furthermore, during the retention test, FMT-aged mice spent less time in the target quadrant that contained the escape tunnel compared to control groups (Fig. 3b; heat map in Fig. 3c). The values represent the mean ± SEM for each group (n = 10–12 mice/group). *P < 0.05 vs control animals and FMT-adult. The novel object recognition test (Fig. 3d–e): on day 1, mice were exposed to two similar objects (A + A); on day 2, animals were re-exposed to the testing area containing one novel object (A + B). The time spent by the animals exploring each object was recorded. The discrimination index, calculated as (TB-TA)/(TB + TA), was used to assess the preference for the novel object. Control groups, either untreated or FMT-adult mice, preferred the novel object more than the familiar one, whereas FMT-aged mice showed a significant reduction in the time spent exploring the novel object (heat map in 3e) suggesting reduced discrimination as a consequence of impaired memory capabilities. The values represent the mean ± SEM for each group (n = 10–12 mice/group). **P < 0.01 vs control animals