The neural correlates of hand and foot action recognition in individuals born without upper limbs

[摘要] Do we need the motor system to process and recognize the actions of others? According to motor theories we recognize actions by covertly imitating observed actions. This view has recently been challenged by two lines of evidence: neuroimaging studies show that the lateral occipitotemporal cortex (LOTC) and inferior parietal lobe (IPL) encode feature-invariant action representations whereas premotor cortex (PMC) seems to code concrete action features only; furthermore, behavioral studies demonstrate that individuals born without upper limbs recognize hand actions, that they cannot covertly imitate, with the same efficiency as control participants. However, it could be that in typically developed individuals access to higher level hand action representations in LOTC and IPL is subsequent to motor simulation of concrete actions in PMC, and that in subjects without upper limbs access to those higher level representations is based on different (compensatory) neurocognitive mechanisms drawing on other brain regions like the mentalizing network. This fMRI study aimed at addressing these possibilities. We scanned five dysplasic individuals (IDs) born without upper limbs and typically developed participants when watching videos of actions executed with lower and upper limbs (open and close doors and trash bins). We found similar significant decoding of hand actions in LOTC and IPL of both the IDs and the controls, demonstrating that access to higher level action representations in LOTC and IPL does not require motor simulation. Second, at odds with the hypothesis that the IDs recruit compensatory neurocognitive mechanisms to recognize hand actions, we found similar neural activity and cluster locations in PMC, LOTC, and IPL with regard to hand and foot actions in the IDs and the controls, and no trace of increased neural activity or decoding of hand actions in other brain regions of the IDs. These findings suggest that action recognition relies on visual, not motor, processing.

[学科分类] 眼科学