Interpersonal Liking Modulates Motor-Related Neural Regions

Observing someone perform an action engages brain regions involved in motor planning, such as the inferior frontal, premotor, and inferior parietal cortices. Recent research suggests that during action observation, activity in these neural regions can be modulated by membership in an ethnic group defined by physical differences. In this study we expanded upon previous research by matching physical similarity of two different social groups and investigating whether likability of an outgroup member modulates activity in neural regions involved in action observation. Seventeen Jewish subjects were familiarized with biographies of eight individuals, half of the individuals belonged to Neo-Nazi groups (dislikable) and half of which did not (likable). All subjects and actors in the stimuli were Caucasian and physically similar. The subjects then viewed videos of actors portraying the characters performing simple motor actions (e.g. grasping a water bottle and raising it to the lips), while undergoing fMRI. Using multivariate pattern analysis (MVPA), we found that a classifier trained on brain activation patterns successfully discriminated between the likable and dislikable action observation conditions within the right ventral premotor cortex. These data indicate that the spatial pattern of activity in action observation related neural regions is modulated by likability even when watching a simple action such as reaching for a cup. These findings lend further support for the notion that social factors such as interpersonal liking modulate perceptual processing in motor-related cortices.

观察他人执行动作时，会激活参与运动规划的脑区，例如额下回（inferior frontal cortex）、运动前区（premotor cortex）以及顶下小叶皮层（inferior parietal cortices）。近期研究表明，在动作观察过程中，这些脑区的神经活动会受到基于生理差异定义的族群归属的调节。本研究通过匹配两类社会群体的生理相似性，并探究外群体成员的好感度是否会调节动作观察相关脑区的活动，以此拓展了此前的研究。本研究招募了17名犹太籍被试，先让被试熟悉8名角色的背景资料：其中4名隶属于新纳粹（Neo-Nazi）群体（属于令人反感的外群体），另外4名则不属于该群体（属于令人有好感的外群体）。所有被试与刺激材料中的演员均为高加索人（Caucasian），且生理特征高度相似。随后，被试在接受功能磁共振成像（fMRI，functional magnetic resonance imaging）扫描的同时，观看演员扮演上述角色执行简单运动动作的视频（例如握住水瓶并举至唇边）。本研究采用多变量模式分析（MVPA，multivariate pattern analysis）发现：在右侧腹侧运动前皮层内，基于脑激活模式训练的分类器能够成功区分令人有好感与令人反感的动作观察条件。上述结果表明，即便在观察诸如伸手拿取水杯这类简单动作时，动作观察相关脑区的活动空间模式仍会受到好感度的调节。本研究结果进一步支持了这一观点：诸如人际好感这类社会因素，会调节运动相关皮层的知觉加工过程。