PT  - JOURNAL ARTICLE
AU  - Joan López-Moliner
AU  - Cécile Vullings
AU  - Laurent Madelain
AU  - Robert J. van Beers
TI  - Prediction and final temporal errors are used for trial-to-trial motor corrections
AID  - 10.1101/368001
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 368001
4099  - http://biorxiv.org/content/early/2018/07/12/368001.short
4100  - http://biorxiv.org/content/early/2018/07/12/368001.full
AB  - Correction on the basis of previous errors is paramount to sensorimotor learning. While corrections of spatial errors have been studied extensively, little is known about corrections of previous temporal errors. We tackled this problem in different conditions involving arm movements (AM), saccadic eye movements (SM) or button presses (BP). The task was to intercept a moving target at a designated zone (i. e. no spatial error) either with the hand sliding a pen on a graphics tablet (AM), a saccade (SM) or a button press (BP) that released a cursor moving ballistically for a fixed time of 330 ms. The dependency of the final temporal error on action onset varied from “low” in AM (due to possible online corrections) to “very high” in the other conditions (i.e. open loop). The lag-1 cross-correlation between action onset and the previous temporal error were close to zero in all conditions suggesting that people minimized temporal variability of the final errors across trials. Interestingly, in conditions SM and BP, action onset did not depend on the previous temporal error. However, this dependency was clearly modulated by the movement time in the AM condition: faster movements depended less on the previous actual temporal error. An analysis using a Kalman filter confirmed that people in SM, BP and AM involving fast movements used the prediction error (i.e. intended action onset minus actual action onset) for next trial correction rather than the final target error. A closer look at the AM condition revealed that both error signals were used and that the contribution of each signal follows different patterns with movement time: as movement progresses the reliance on the prediction error decreases non-linearly and that on the final error increases linearly.Author summary Many daily life situations (e.g. dodging an approaching object or hitting a moving target) require people to correct planning of future movements on the basis of previous temporal errors. This is paramount to learning motor skills. However the actual temporal error can be difficult to measure or perceive: imagine, for example, a baseball batter that swings and misses a fastball. Here we show that in these kinds of situations people can use an internal error signal to make corrections in the next trial. This signal is based on the discrepancy between the actual action onset and the expected one. The relevance of this error decreases with the movement time of the action in a particular way while the final actual temporal error gains relevance for the next trial with longer motor durations.