Anticipating reward improves learning during sleep
According to a study by Fischer and Born, published in the most recent journal of SLEEP, they found that merely anticipating a reward can determine the amount of memory consolidation during those important times of offline processing.
The authors split up 76 adult subjects (20-33) into wake and sleep groups. All subjects learned a finger sequence tapping task with their non dominant hand and all subjects except for the control groups were told that additional payment would be contingent upon their improvement after the retention interval (12 hrs).
Results showed that overall motor skill improvement was seen exclusively in the sleep condition. Furthermore, they found that sleep induced a significant improvement that was associated with the anticipated reward before the retention interval compared to the nonreward associated sequence. However, the authors note that circadian factors and mental rehearsal during retention could've partially confounded their findings.
So for all the future professional finger tappers out there, get that sleep, but make sure to really believe you'll be greatly rewarded for your unrelenting efforts.
Fischer S, & Born J (2009). Anticipated reward enhances offline learning during sleep. Journal of experimental psychology. Learning, memory, and cognition, 35 (6), 1586-93 PMID: 19857029