Abstract
Physical practice often causes fatigue that can temporarily decrease motor skill execution and increase errors at the end of a training session. Whether these erroneous last movements impair the ability to remember successful movements performed earlier is unknown. To answer this question, participants performed a visuomotor adaptation task in which they adapted their reaching movements to a 25° counterclockwise rotation of the visual representation of their hand. Unknown to the participants, the rotation was gradually ramped up to 37° over the last 64 trials of the training session and a ±7.5° variation was introduced pseudo-randomly on 38% of these trials (VariedRamp group). This resulted in participants gradually drifting away from 25° while perceiving frequent and large errors. A second group was exposed only to a 25° rotation during the first session (Steady25 group) and a third group was exposed to the ramp up but without the pseudo-random variation (thus drifting away from 25° but without perceiving large errors; GradualRamp group). Adaptation was assessed by measuring movement direction 100ms after movement onset. Results revealed that both the VariedRamp and GradualRamp groups demonstrated a more pronounced clockwise bias at the end of the training session compared to the Steady25 group (p < .05). A similar bias was also apparent for both groups in a no-vision retention test performed 24h later. Our results therefore suggest that erroneous and successful movements performed at the end of a practice session have similar effects on the retention of the movements performed earlier.
