From Observed Action Identity to Social Affordances

• Published in: Trends in cognitive sciences Vol. 25; no. 6; pp. 493 - 505
• Main Authors: Orban, G.A., Lanzilotto, M., Bonini, L.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.06.2021
• Subjects: action observation; area AIP; parietal cortex; social interaction; visual invariance; visual invariance; social interaction; parietal cortex; area AIP; action observation
• ISSN: 1364-6613; 1879-307X
• DOI: 10.1016/j.tics.2021.02.012

Others’ observed actions cause continuously changing retinal images, making it challenging to build neural representations of action identity. The monkey anterior intraparietal area (AIP) and its putative human homologue (phAIP) host neurons selective for observed manipulative actions (OMAs). The neuronal activity of both AIP and phAIP allows a stable readout of OMA identity across visual formats, but human neurons exhibit greater invariance and generalize from observed actions to action verbs. These properties stem from the convergence in AIP of superior temporal signals concerning: (i) observed body movements; and (ii) the changes in the body–object relationship. We propose that evolutionarily preserved mechanisms underlie the specification of observed-actions identity and the selection of motor responses afforded by them, thereby promoting social behavior. A substantial fraction of neurons in the monkey anterior intraparietal area (AIP) and its human homologue phAIP are selective for observed manipulative actions (OMAs).OMA selective neurons encode the identity of the observed actions, up to the level of semantic representation in phAIP.OMA identity may result from the combination of two visual signals originating in the superior temporal sulcus (STS) and concerning: (i) observed body movements: and (ii) the changes in the hand/object relationship (action effects).Others’ observed actions, beyond grasping, may be specified in parietal territories, underpinning ‘social affordance’ processing and the selection of potential behavioral responses in parieto-premotor circuits.