Cortical response when a semantic anomaly is detected in action representation. A LORETA source analysis

The strength relationship between action and language was largely discussed. When perception of plausible or implausible actions within a context is performed a specific semantic process is activated, which was shown to be similar in nature to the processing of anomalous linguistic information. In the present research it was considered the cortical response to the semantic incongruence induced by an anomalous object-related action, within an actions’ sequence. We examined the action representation and semantic processes indexed by event-related potentials ERPs (N400 effect) when plausible (congruous) or implausible (incongruous) actions were performed within a dynamic context (video tapes showing a sequence of four action frames). The N400 effect was explored using a paradigm from neurolinguistic studies, which showed the amplitude of N400 was larger for critical words that were semantically incongruous or unrelated to preceding words. However, the cortical regions involved in the semantic anomaly processing need to be examined as a function of the stimulus category (linguistic vs. action). Indeed, the N400 effect was shown to have a more anterior distribution for action than for linguistic contexts. Seventeen participants performed an explicit task to distinguish congruous from incongruous final target action. We provided specific contextual constraints where the final frame of a sequence of actions (three preceding actions) represented the congruous/incongruous ending. The semantic anomaly consisted of a gesture that did not have the semantic properties required to perform for the action-goal (functionally unusual). That is, the action was in opposition with the goal-related and intention-related requirements to perform that gesture. ERP analysis and cortical source analysis (LORETA) showed a significant N400-like effect more frontally (DLPFC) and temporo-parietally (left supramarginal gyrus) distributed in response to incongruous condition. Two possible explanations were proposed. The N400-like would be correlated with an increased difficulty to access the semantic memory networks in comprehension or it would be related to the integrative processing capacity necessary to configure new semantic representations. Moreover it can be argued that the N400-like effect is similar in nature to the N400, which is generally evoked by linguistic stimuli. Nevertheless, the present research showed also significant differences between the cortical generators of action processing and linguistic processing. This fact may be explained by assuming that objectrelated action representations activate a specific cortical network, more frontally distributed, directly related to congruous/incongruous object use comprehension.