Univ. Lille, CNRS, UMR 9193-SCALab-Sciences Cognitives et Sciences Affectives, Lille, France.
PLoS One. 2018 May 17;13(5):e0196874. doi: 10.1371/journal.pone.0196874. eCollection 2018.
Peripersonal space is a multisensory representation of the environment around the body in relation to the motor system, underlying the interactions with the physical and social world. Although changing body properties and social context have been shown to alter the functional processing of space, little is known about how changing the value of objects influences the representation of peripersonal space. In two experiments, we tested the effect of modifying the spatial distribution of reward-yielding targets on manual reaching actions and peripersonal space representation. Before and after performing a target-selection task consisting of manually selecting a set of targets on a touch-screen table, participants performed a two-alternative forced-choice reachability-judgment task. In the target-selection task, half of the targets were associated with a reward (change of colour from grey to green, providing 1 point), the other half being associated with no reward (change of colour from grey to red, providing no point). In Experiment 1, the target-selection task was performed individually with the aim of maximizing the point count, and the distribution of the reward-yielding targets was either 50%, 25% or 75% in the proximal and distal spaces. In Experiment 2, the target-selection task was performed in a social context involving cooperation between two participants to maximize the point count, and the distribution of the reward-yielding targets was 50% in the proximal and distal spaces. Results showed that changing the distribution of the reward-yielding targets or introducing the social context modified concurrently the amplitude of self-generated manual reaching actions and the representation of peripersonal space. Moreover, a decrease of the amplitude of manual reaching actions caused a reduction of peripersonal space when resulting from the distribution of reward-yielding targets, while this effect was not observed in a social interaction context. In that case, the decreased amplitude of manual reaching actions was accompanied by an increase of peripersonal space representation, which was not due to the mere presence of a confederate (control experiment). We conclude that reward-dependent modulation of objects values in the environment modifies the representation of peripersonal space, when resulting from either self-generated motor actions or observation of motor actions performed by a confederate.
个体空间是身体周围环境与运动系统的多感觉表示，是与物理和社会世界相互作用的基础。尽管已经表明改变身体属性和社会环境会改变空间的功能处理，但对于改变物体的价值如何影响个体空间的表示知之甚少。在两项实验中，我们测试了改变产生奖励的目标的空间分布对手动到达动作和个体空间表示的影响。在执行目标选择任务之前和之后，参与者执行了一项二选一强制选择可达性判断任务。在目标选择任务中，一半的目标与奖励相关联（颜色从灰色变为绿色，提供 1 分），另一半与奖励无关（颜色从灰色变为红色，不提供分数）。在实验 1 中，目标选择任务是个人完成的，目的是最大限度地提高分数，奖励产生的目标的分布在近端和远端空间中分别为 50%、25%或 75%。在实验 2 中，目标选择任务是在涉及两个参与者合作以最大限度地提高分数的社会环境中完成的，奖励产生的目标的分布在近端和远端空间中为 50%。结果表明，改变奖励产生目标的分布或引入社会环境会同时改变自我产生的手动到达动作的幅度和个体空间的表示。此外，当奖励产生的目标分布导致手动到达动作幅度减小时，会导致个体空间的缩小，而在社会互动环境中则观察不到这种效应。在这种情况下，手动到达动作幅度的减小伴随着个体空间表示的增加，这不是由于同伴的存在（对照实验）。我们的结论是，环境中物体价值的奖励依赖性调制会改变个体空间的表示，无论是源自自我产生的运动动作还是观察同伴执行的运动动作。
