Catch trials in force field learning influence adaptation and consolidation of human motor memory

Abstract

Force field studies are a common tool to investigate motor adaptation and consolidation. Thereby, subjects usually adapt their reaching movements to force field perturbations induced by a robotic device. In this context, so-called catch trials, in which the disturbing forces are randomly turned off, are commonly used to detect after-effects of motor adaptation. However, catch trials also produce sudden large motor errors that might influence the motor adaptation and the consolidation process. Yet, the detailed influence of catch trials is far from clear. Thus, the aim of this study was to investigate the influence of catch trials on motor adaptation and consolidation in force field experiments. Therefore, 105 subjects adapted their reaching movements to robot-generated force fields. The test groups adapted their reaching movements to a force field A followed by learning a second interfering force field B before retest of A (ABA). The control groups were not exposed to force field B (AA). To examine the influence of diverse catch trial ratios, subjects received catch trials during force field adaptation with a probability of either 0, 10, 20, 30, or 40%, depending on the group. First, the results on motor adaptation revealed significant differences between the diverse catch trial ratio groups. With increasing amount of catch trials, the subjects' motor performance decreased and subjects' ability to accurately predict the force field—and therefore internal model formation—was impaired. Second, our results revealed that adapting with catch trials can influence the following consolidation process as indicated by a partial reduction to interference. Here, the optimal catch trial ratio was 30%. However, detection of consolidation seems to be biased by the applied measure of performance.

Contextual Interference Effect Is Independent of Retroactive Inhibition but Variable Practice Is Not Always Beneficial

“…Therefore, it might be that a lower amount of motor variability during practice would lead to the same consolidation benefits but would also lead to better absolute performance values of the Random compared to the Blocked or the Constant group. This would indicate that the beneficial potential of variable practice depends on the right amount of variability during practice (Stockinger et al, 2014).…”

Mechanisms within the Parietal Cortex Correlate with the Benefits of Random Practice in Motor Adaptation

“…However, this force field prediction cannot entirely counteract the dynamic uncertainty during movement execution under random force field conditions. Therefore, subjects of the random group must have used either some sort of control strategy (impedance control or reflex modulation) or online feedback mechanisms to perform similar to the subjects of the blocked group ( Franklin et al, 2012 ; Stockinger et al, 2014 ). Usage of an impedance strategy would lead to a minor variability in the PDmax and to a decreased reliance on force field prediction in the random group.…”

Pushing attention to one side: Force field adaptation alters neural correlates of orienting and disengagement of spatial attention

“…The force profiles, velocity and kinematic profiles were resampled to 100 data points evenly spread in the y‐direction between movement start and the reach at target extent. For each participant, we subtracted the average baseline force profile from each channel trial to correct for pre‐existing biases in direction‐dependant forces (Stockinger, Focke, & Stein, ; Wei, Wert, & Körding, ). To characterise feedforward adaptation, we analysed the mean perpendicular force exerted against the channel wall divided by mean hand speed in the baseline‐corrected channel trial force profiles.…”