Abstract
When observing others' behavior, it is important to perceive not only the identity of the observed actions (OAs), but also the number of times they were performed. Given the mounting evidence implicating posterior parietal cortex in action observation, and in particular that of manipulative actions, the aim of this study was to identify the parietal region, if any, that contributes to the processing of observed manipulative action (OMA) numerosity, using the functional magnetic resonance imaging technique. Twenty‐one right‐handed healthy volunteers performed two discrimination tasks while in the scanner, responding to video stimuli in which an actor performed manipulative actions on colored target balls that appeared four times consecutively. The subjects discriminated between two small numerosities of either OMAs (“Action” condition) or colors of balls (“Ball” condition). A significant difference between the “Action” and “Ball” conditions was observed in occipito‐temporal cortex and the putative human anterior intraparietal sulcus (phAIP) area as well as the third topographic map of numerosity‐selective neurons at the post‐central sulcus (NPC3) of the left parietal cortex. A further region of interest analysis of the group‐average data showed that at the single voxel level the latter area, more than any other parietal or occipito‐temporal numerosity map, favored numerosity of OAs. These results suggest that phAIP processes the identity of OMAs, while neighboring NPC3 likely processes the numerosity of the identified OAs.
Highlights
Social interactions belong to the core of human behavior, underscoring the importance of perceptual mechanisms processing visual signals arising from others' actions (Platonov & Orban, 2016, 2017)
The exemplars of a given class are processed by observed action (OA) selective neurons, as has been shown for observed manipulative actions (OMAs) in monkey anterior intraparietal (AIP) area (Lanzilotto et al, 2019) and its human homologue, putative human anterior intraparietal sulcus
It has been proposed that the processing of visual identity of OA is one of the main signals used by subjects in the planning of own actions (Lanzilotto et al, 2019), which very frequently are made in response to
Summary
Social interactions belong to the core of human behavior, underscoring the importance of perceptual mechanisms processing visual signals arising from others' actions (Platonov & Orban, 2016, 2017). OA identity, as it is used here, is a purely visual notion that applies in first instance to conspecifics, and is very different from the abstract concepts of action verbs that may apply to many living creatures and even objects (e.g., running water). It does not include the actor, nor the object, target of the action, nor the scene (Orban, 2018). It has been proposed that the processing of visual identity of OA is one of the main signals used by subjects in the planning of own actions (Lanzilotto et al, 2019), which very frequently are made in response to
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