The number of effectors limits the relative sleep gain: Insights from seven finger tapping experiments

The role of sleep in motor memory consolidation is still a matter of ongoing debate. A classic task to investigate mechanisms of motor memory consolidation is the finger tapping task, which reliably shows small effects in performance enhancement after sleep but not after a corresponding wake interval. However, variants of the task with a varying number of effectors (e.g., one hand) failed to demonstrate this effect on motor memory consolidation. Thus, in a series of seven experiments we investigate five variants of the classic finger tapping task in which the number of effectors (1 or 2 hands combined with 1, 2 or 4 fingers) used to perform the task are systematically varied. For the groups, where sleep immediately followed learning, a beneficial effect of sleep in comparison with a corresponding wake interval was found, except for the task variant where the finger tapping task was performed with 1 hand and 1 finger. However, no clear-cut pattern could be identified for the numbers of effectors used to perform the task and the magnitude of offline motor memory consolidation. Furthermore, for groups with an intervening wake interval between learning and sleep no differences between the post-sleep and post-wake gain were observed. HighlightsIn a variation of the classical finger tapping task with one hand and one finger, no sleep-dependent enhancement was found. In all other variations, small to large effects of sleep-dependent offline-gains were found. An interposed wake interval between learning and sleep substantially diminishes the post-sleep enhancement. Motor skill complexity, with respect to the coordination of more than one effector, does partially play a role in predicting sleep-dependent motor memory enhancement.