Search Abstracts | Symposia | Slide Sessions | Poster Sessions
Multimodal evidence for the integration of semantic and sensorimotor representations during the comprehension of naturalistic actions
Poster Session C, Saturday, September 13, 11:00 am - 12:30 pm, Field House
Laura de Frutos Sagastuy1,2, Cesar Caballero-Gaudes1,3, Ileana Quiñones3,4, Manuel Carreiras1,2,3, Lucia Amoruso1,3,5; 1Basque center on Cognition, Brain and Language, BCBL, 2Universidad del Pais Vasco, UPV-EHU, 3Ikerbasque, Basque Foundation for Science, 4Biogipuzkoa Health Research Institute, 5Cognitive Neuroscience Center (CNC), University of San Andres
Our brain is remarkably adept at decoding the intentions underlying others’ behaviors, allowing us to navigate complex social environments with precision. This ability is thought to rely on the dorsal Action Observation Network (AON), a core neural system that maps others’ actions onto the observer’s motor repertoire. Recent evidence, however, suggests that naturalistic action comprehension recruits a broader network extending beyond the AON. Specifically, regions along a ventral occipito-temporal gradient leverage object-based knowledge to generate an early “semantic prior” about the most plausible intention, which is then relayed to the AON for integration with sensorimotor representations. Yet, the neural mechanisms governing the temporal unfolding and interaction of semantic and motor processes remain partially understood. In this study, we combined functional MRI (fMRI) and magnetoencephalography (MEG) to examine the spatial and spectro-temporal dynamics of context-based action comprehension in 30 healthy participants. Participants viewed images of incomplete, everyday actions and were asked to infer the overarching intention. Crucially, actions were embedded in either congruent (e.g., reaching to grasp a full cup with a precision grip) or incongruent (e.g., reaching to grasp an empty cup with a precision grip) contexts. This manipulation—particularly the incongruent condition—enabled us to dissociate the contributions of sensorimotor and object-based semantic knowledge to action understanding. fMRI results revealed the engagement of canonical AON nodes, including dorsal fronto-parietal regions, and extended into ventral occipito-temporal areas involved in semantic processing and object recognition. Context congruence effects emerged in a predominantly left-lateralized network encompassing parietal and temporal cortices. MEG data further elucidated the spectro-temporal unfolding of these effects. Action comprehension elicited left-lateralized desynchronization in the mu rhythm (8–14 Hz) across fronto-parietal and occipito-temporal regions, with stronger suppression for incongruent compared to congruent actions. Representational Similarity Analysis revealed that neural activity patterns were significantly explained by both an object-based semantic model and a grip-related sensorimotor model. Importantly, the semantic model showed an earlier peak in model fit (~150 ms), while the sensorimotor model peaked later (~220 ms), consistent with a temporal progression from semantic access to sensorimotor updating. Together, these findings provide converging spatial and temporal evidence for the integration of semantic and sensorimotor knowledge during naturalistic action comprehension, offering new insights into the neural dynamics supporting this key social ability.
Topic Areas: Multisensory or Sensorimotor Integration,