The dual-action simulation hypothesis proposes that both an observed and an imagined action can be represented simultaneously in the observer's brain. These two sensorimotor streams would either merge or compete depending on their relative suitability for action planning. To test this hypothesis, three forms of combined action observation and motor imagery (AO + MI) instructions were used in this repeated-measures experiment. Participants observed index finger abduction-adduction movements while imagining the same action (congruent AO + MI), little finger abduction-adduction (coordinative AO + MI), or a static hand (conflicting AO + MI). Single-pulse transcranial magnetic stimulation was applied to the left primary motor cortex. The amplitude of motor evoked potential responses were recorded from both the first dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles of the right-hand while eye movements were tracked. When controlling for the influence of relevant eye movements, corticospinal excitability was facilitated relative to control conditions in the concurrently observed and imagined muscles for both congruent and coordinative AO + MI conditions. Eye-movement metrics and social validation data from post-experiment interviews provided insight into the attentional and cognitive mechanisms underlying these effects. The findings provide empirical support for the dual-action simulation hypothesis, indicating for the first time that it is possible to co-represent observed and imagined actions simultaneously.

中文翻译：

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在动作观察过程中，神经生理学标志物区分运动图像的不同形式。

双重动作模拟假设提出，可以同时在观察者的大脑中表示观察到的动作和想象到的动作。这两种感觉运动流将根据其对行动计划的相对适合性而合并或竞争。为了验证该假设，在此重复测量实验中使用了三种形式的联合动作观察和运动图像（AO + MI）指令。参与者观察到在想象相同动作（一致的AO + MI），小手指绑架-内收（协调AO + MI）或静止的手（冲突的AO + MI）时，食指外展-内收运动。将单脉冲经颅磁刺激应用于左初级运动皮层。在跟踪眼球运动的同时，记录了右手第一背骨间（FDI）和小指外展肌（ADM）的运动诱发电位响应的幅度。当控制相关眼球运动的影响时，相对于同时观察到的和想象中的AO + MI状况的肌肉中的控制状况，皮质脊髓兴奋性相对于控制状况得到了促进。来自实验后访谈的眼动指标和社会验证数据提供了对引起这些效应的注意力和认知机制的见解。这些发现为双作用模拟假说提供了经验支持，这首次表明有可能同时共同代表观察到的和想象的行为。