Zhong Shan, Pouratian Nader, Christopoulos Vassilios
Neuroscience Graduate Program, University of California Riverside, Riverside, California, United States of America.
Alfred E. Mann Department of Biomedical Engineering, University of Southern California, Los Angeles, California, United States of America.
PLoS Comput Biol. 2025 Feb 10;21(2):e1012811. doi: 10.1371/journal.pcbi.1012811. eCollection 2025 Feb.
Survival of species in an ever-changing environment requires a flexibility that extends beyond merely selecting the most appropriate actions. It also involves readiness to stop or switch actions in response to environmental changes. Although considerable research has been devoted to understanding how the brain switches actions, the computations underlying the switching process and how it relates to the selecting and stopping processes remain elusive. A normative theory suggests that switching is simply an extension of the stopping process, during which a current action is first inhibited by an independent pause mechanism before a new action is generated. This theory was challenged by the affordance competition hypothesis, according to which the switching process is implemented through a competition between the current and new actions, without engaging an independent pause mechanism. To delineate the computations underlying these action regulation functions, we utilized a neurocomputational theory that models the process of selecting, stopping and switching reaching movements. We tested the model predictions in healthy individuals who performed reaches in dynamic and uncertain environments that often required stopping and switching actions. Our findings suggest that unlike the stopping process, switching does not necessitate a proactive pause mechanism to delay movement initiation. Hence, the switching and stopping processes seem to be implemented by different mechanisms at the planning phase of the reaching movement. However, once the reaching movement has been initiated, the switching process seems to involve an independent pause mechanism if the new target location is unknown prior to movement initiation. These findings offer a new understanding of the computations underlying action switching, contribute valuable insights into the fundamental neuroscientific mechanisms of action regulation, and open new avenues for future neurophysiological investigations.
在不断变化的环境中，物种的生存需要一种灵活性，这种灵活性不仅仅是选择最恰当的行动。它还包括准备好根据环境变化停止或切换行动。尽管已经有大量研究致力于理解大脑如何切换行动，但切换过程背后的计算以及它与选择和停止过程的关系仍然难以捉摸。一种规范理论认为，切换仅仅是停止过程的延伸，在此过程中，当前行动首先被一个独立的暂停机制抑制，然后才产生新的行动。这一理论受到了可供性竞争假说的挑战，根据该假说，切换过程是通过当前行动和新行动之间的竞争来实现的，而无需独立的暂停机制。为了描绘这些行动调节功能背后的计算，我们运用了一种神经计算理论，该理论对选择、停止和切换伸手动作的过程进行建模。我们在健康个体中测试了模型预测，这些个体在动态且不确定的环境中进行伸手动作，这种环境常常需要停止和切换行动。我们的研究结果表明，与停止过程不同，切换并不一定需要一个主动的暂停机制来延迟动作启动。因此，在伸手动作的规划阶段，切换和停止过程似乎是由不同的机制实现的。然而，一旦伸手动作开始，如果新的目标位置在动作启动前未知，切换过程似乎涉及一个独立的暂停机制。这些发现为行动切换背后的计算提供了新的理解，为行动调节的基本神经科学机制提供了有价值的见解，并为未来的神经生理学研究开辟了新的途径。
