The space around our body, the so-called peripersonal space, is where interactions with nearby objects may occur. “Defensive space” and “Reaching space”, respectively, refer to two opposite poles of interaction between our body and the external environment: protecting the body and performing a goal-directed action. Here, we hypothesized that mechanisms underlying these two action spaces are differentially modulated by the valence of visual stimuli, as stimuli with negative valence are more likely to activate protective actions whereas stimuli with positive valence may activate approaching actions. To test whether such distinction in cognitive/evaluative processing exists between Reaching and Defensive spaces, we measured behavioral responses as well as neural activations over sensorimotor cortex using EEG while participants performed several tasks designed to tap into mechanisms underlying either Defensive (e.g., respond to touch) or Reaching space (e.g., estimate whether object is within reaching distance). During each task, pictures of objects with either positive or negative valence were presented at different distances from the participants' body. We found that Defensive space was smaller for positively compared with negatively valenced visual stimuli. Furthermore, sensorimotor cortex activation (reflected in modulation of beta power) during tactile processing was enhanced when coupled with negatively rather than positively valenced visual stimuli regarding Defensive space. On the contrary, both the EEG and behavioral measures capturing the mechanisms underlying Reaching space did not reveal any modulation by valence. Thus, although valence encoding had differential effects on Reaching and Defensive spaces, the distance of the visual stimulus modulated behavioral measures as well as activity over sensorimotor cortex (reflected in modulations of mu power) in a similar way for both types of spaces. Our results are compatible with the idea that Reaching and Defensive spaces involve the same distance-dependent neural representations of sensory input, whereas task goals and stimulus valence (i.e., contextual information) are implemented at a later processing stage and exert an influence on motor output rather than sensory/space encoding.

我们身体周围的空间，即所谓的个人周围空间，是与附近物体可能发生交互的地方。 “防御空间”和“到达空间”分别指的是我们的身体与外部环境相互作用的两个相反的极点：保护身体和执行目标导向的行动。在这里，我们假设这两个动作空间背后的机制受到视觉刺激效价的差异调节，因为具有负价的刺激更有可能激活保护行为，而具有正价的刺激可能会激活接近的行为。为了测试触及空间和防御空间之间是否存在认知/评估处理的这种区别，我们使用脑电图测量了感觉运动皮层的行为反应和神经激活，同时参与者执行了几项旨在挖掘防御空间背后机制的任务（例如，对触摸做出反应） ）或到达空间（例如，估计物体是否在到达距离内）。在每项任务中，在距参与者身体不同距离处呈现具有正价或负价的物体的图片。我们发现，与负价视觉刺激相比，正价视觉刺激的防御空间更小。此外，当与防御空间相关的负价视觉刺激而不是正价视觉刺激相结合时，触觉处理过程中感觉运动皮层的激活（反映在β功率的调节中）得到增强。相反，脑电图和行为测量捕获到达空间的机制并没有显示任何效价的调节。 因此，虽然价编码对到达空间和防御空间有不同的影响，但视觉刺激的距离以类似的方式调节行为测量以及感觉运动皮层的活动（反映在μ功率的调节中）。我们的结果与以下观点相一致：到达空间和防御空间涉及相同的感觉输入的距离相关神经表征，而任务目标和刺激效价（即上下文信息）在稍后的处理阶段实现并对运动输出产生影响而不是感觉/空间编码。