Teunissen Lonneke, Selen Luc P J, Medendorp W Pieter
Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, The Netherlands.
J Neurophysiol. 2023 Mar 1;129(3):733-748. doi: 10.1152/jn.00223.2022. Epub 2023 Feb 22.
Motor costs influence movement selection. These costs could change when movements are adapted in response to errors. When the motor system attributes the encountered errors to an external cause, appropriate movement selection requires an update of the movement goal, which prompts the selection of a different control policy. However, when errors are attributed to an internal cause, the initially selected control policy could remain unchanged, but the internal forward model of the body needs to be updated, resulting in an online correction of the movement. We hypothesized that external attribution of errors leads to the selection of a different control policy, and thus to a change in the expected cost of movements. This should also affect subsequent motor decisions. Conversely, internal attribution of errors may (initially) only evoke online corrections, and thus is expected to leave the motor decision process unchanged. We tested this hypothesis using a saccadic adaptation paradigm, designed to change the relative motor cost of two targets. Motor decisions were measured using a target selection task between the two saccadic targets before and after adaptation. Adaptation was induced by either abrupt or gradual perturbation schedules, which are thought to induce more external or internal attribution of errors, respectively. By taking individual variability into account, our results show that saccadic decisions shift toward the least costly target after adaptation, but only when the perturbation is abruptly, and not gradually, introduced. We suggest that credit assignment of errors not only influences motor adaptation but also subsequent motor decisions. Decisions between potential motor actions are influenced by their costs, but costs change when movements are adapted. Using a saccadic target selection task, we show that target preference shifts after abrupt, but not after gradual adaptation. We suggest that this difference emerges because abrupt adaptation results in target remapping, and thus directly influences cost calculations, whereas gradual adaptation is mainly driven by corrections to a forward model that is not involved in cost calculations.
运动成本会影响运动选择。当运动因误差而进行调整时，这些成本可能会发生变化。当运动系统将遇到的误差归因于外部原因时，合适的运动选择需要更新运动目标，这会促使选择不同的控制策略。然而，当误差归因于内部原因时，最初选择的控制策略可能保持不变，但身体的内部前向模型需要更新，从而导致运动的在线校正。我们假设误差的外部归因会导致选择不同的控制策略，进而导致运动预期成本的变化。这也应该会影响后续的运动决策。相反，误差的内部归因可能（最初）只会引发在线校正，因此预计不会改变运动决策过程。我们使用扫视适应范式来测试这一假设，该范式旨在改变两个目标的相对运动成本。在适应前后，使用两个扫视目标之间的目标选择任务来测量运动决策。适应是由突然或逐渐的扰动计划诱导的，据认为分别会导致更多的误差外部或内部归因。通过考虑个体差异，我们的结果表明，适应后扫视决策会转向成本最低的目标，但只有在突然引入扰动而不是逐渐引入扰动时才会如此。我们认为误差的归因不仅会影响运动适应，还会影响后续的运动决策。潜在运动动作之间的决策受其成本影响，但运动调整时成本会发生变化。使用扫视目标选择任务，我们表明突然适应后目标偏好会发生变化，而逐渐适应后则不会。我们认为这种差异的出现是因为突然适应会导致目标重新映射，从而直接影响成本计算，而逐渐适应主要是由对不参与成本计算的前向模型的校正驱动的。
