Daytime naps consolidate Cantonese tone learning through promoting cross-talker perception: The role of prior knowledge

This study investigates whether daytime naps facilitate perceptual learning of Cantonese tones and how prior knowledge mediates the consolidation effect. Ninety Mandarin native speakers were pseudo-randomly assigned to either a nap group, who napped for 1.5 h with brain activities recorded, or the non-nap group, who rested for 1.5 h. They were trained with Cantonese contour-level tonal contrasts and level-level tonal contrasts, followed by a tone identification task (trained talker) before the nap manipulation, and were re-tested (trained and novel talkers) after the nap. The results showed that naps facilitated Cantonese tone learning, with the nap group outperforming the non-nap group in the cross-talker perception. The cross-talker perception effect was specific to contour-level tonal contrasts (consistent with prior knowledge) and was associated with increased sleep spindles and slow oscillations. The findings suggest that prior knowledge plays an important role in prioritizing contour- level tonal contrasts for memory consolidation.