Role of the left intraparietal sulcus in the comprehension of action intensity described in sentences

Abstract

Abstract From an embodied cognition perspective, semantic processing is assumed to involve sensorimotor representations. The present study used functional magnetic resonance imaging to investigate whether comprehension of action intensity described in sentences is associated with neural representations shared with action execution, particularly those related to grip force. In the execution task, participants gripped their right hand with either high or low force. In the language task, participants evaluated the action intensity described in the sentences. We examined four regions of interest (ROIs): the left primary somatosensory cortex, left primary motor cortex, left dorsal premotor cortex, and the left intraparietal sulcus (LIPS). Multivoxel pattern analysis was used to assess whether intensity information could be decoded within and across tasks. In the execution task, intensity differences were reliably decoded from multivoxel activity patterns across all four regions. In the language task, significant decoding of intensity was observed only in the LIPS. Cross-classification between the execution and language tasks did not reach significance in the primary analysis across the four regions and was associated with low effect sizes. However, exploratory analyses using smaller ROIs revealed significant cross-decoding and moderate effect sizes in the LIPS. These findings suggest that the comprehension of action intensity is associated with higher-level intensity-related representations rather than with neural representations that are closely tied to low-level motor execution. Overall, the results do not support strong embodied accounts, which assume the direct reinstatement of low-level motor execution processes during language comprehension. However, these findings suggest that partially shared higher-level representations of intensity may exist between action execution and language processing.