Selective delayed gains following motor imagery of complex movements.

Recent studies suggest that a night of sleep may play a similar functional role following motor imagery (MI) practice. Here we examined whether offline gains following MI of a finger tapping sequence depends on the degree of complexity of the motor sequence, and whether this improvement differentially affects the individual transitions of the motor-sequence pattern being learned. The data revealed greater delayed performance gains in motor skill procedures that were most difficult, with larger sleep-dependent overnight improvement for movements involving bimanual coordination. The analyses of single transitions between sequence elements further revealed greatest overnight improvement in speed for the slowest (i.e., most difficult) transitions at the re-test. These findings suggest that sleep-related performance gains for imagined movements depend on motor skill complexity, and that difficult transition movements are most effectively enhanced after a night of sleep.