Abstract
The neuronal correlates of action observation in the primate brain have been studied mostly using third-person perspective visual stimuli, reflecting actions performed by others. Recently, several studies have suggested that neurons in the parieto-frontal portion of the monkey action observation network (AON) also display selectivity for first-person perspective, suggesting these motor regions might play a role in self-action monitoring (Maeda et al., 2015; Maranesi et al., 2015). Currently it is not known how different viewpoints of conspecific actions modulate brain responses throughout the monkey AON. Three rhesus monkeys were scanned (Siemens 3T) while fixating videos depicting a monkey hand performing either a reach-and-grasp or reach-and-touch action from three different viewpoints. Viewpoints included viewing angles resembling either a first-person perspective (0 degree), or third-person perspectives (90 degree or 180 degree). Both whole-brain univariate and region-of-interest (ROI) univariate and multi-voxel pattern analyses were performed to investigate the effect of action viewpoint on brain responses in the different sectors of the AON. In line with previous results investigating monkey brain responses during observation of human hand actions (Nelissen et al., 2011; Sharma et al., 2018, Fiave et al., 2018), observing a conspecific hand grasping or reaching yielded significant responses in temporal, parietal and frontal sectors of the AON. ROI analysis showed robust responses not only for third-person, but also for first-person perspective, in STS, parietal AIP and PFG, premotor F5 and ventrolateral prefrontal cortex. Action goals (grasping or reaching) for first-person and for third-person viewpoints could be decoded from both visual, motor and prefrontal regions. Distinct spatial patterns for different viewpoints of the same action were mostly observed in STS and prefrontal regions, with in particular STS showing a generalization of viewpoints across actions. Generalization of action goals across viewpoints was mainly observed in prefrontal cortex, parietal and STS regions.
Acknowledgement: This work was supported by Fonds Wetenschappelijk Onderzoek Vlaanderen (G.0.622.08, G.0.593.09), KU Leuven BOF-ZAP Startfinancing (14/10) and KU Leuven (C14/17/109).