a. The AFR group served as a control with standard rearing; MD refers to the experimental groups, including MD180 and MD360. The pups in the MD180 and MD360 groups were further subdivided into Pre (pre-separation USV) and Post (post-separation USV) groups; five groups (AFR, MD180 Pre, MD180 Post, MD360 Pre, and MD360 Post)were included in the study; b. Mice in the MD groups were separated from their dam and littermates from P1-P14;on P1, P3, P7, P8 and P14, all pups were subjected to USV recording for 5 min. On the testing days, MD180 Pre and MD360 Pre mice were first detected for USVs and then subjected to MD, while MD180 Post and MD360 Post mice were isolated before USV detection.