Positive effects of napping on memory consolidation and resistance against interference.

PURPOSE: This study explored the relationship between naps and memory among habitual nappers in China. METHODS: Medical college students participated and were divided into 30-min, 60-min, and 90-min time-in-bed groups. To evaluate declarative and procedural memory performance, A-B and A-C interfering word pair and interfering finger tapping tasks were employed. RESULTS: Among 60 students, a significant decrease in the correct recall rate in the declarative task after having a nap was found only in the 30-min group (p = 0.005). After learning interference (A-C word pairs), the correct recall rate for the declarative task decreased significantly in all interference tests (ps < 0.001). In the procedural task, the speed of sequence A in the retests increased after having a nap in all three groups (ps < 0.048), with a significant decrease in accuracy only in the 30-min group (p = 0.042). After learning interference (sequence B) in the procedural task, the speed of sequence A increased in the 60-min group after 1 h (p = 0.049), and both the 60-min and 90-min groups showed increased speed after one night (ps < 0.022). No significant improvement in speed was found in the 30-min group (ps > 0.05), and this group showed the lowest accuracy for sequence A (ps < 0.16). CONCLUSION: A habitual nap time-in-bed of 60 or 90 min had better effects on declarative and procedural memory consolidation and better memory resistance against interference in procedural memory.