A saw is first identified as an object used on wood: ERP evidence for temporal differences between Thematic and Functional similarity relations

The role of functional and motor information in manipulable artifact object semantic organization is still poorly understood. In particular, several types of semantic relations involving object functional knowledge may be distinguished. Functional similarity relations group objects with similar functions at relatively specific (e.g. saw-axe, both used to cut wood) or general (saw-knife, both used to cut) levels. Thematic relations group objects based on their complementarity in events (saw used upon/with wood). Recent eye-tracking data showed distinct temporal time courses for the different semantic relations, with fastest processing of thematic relations and slowest processing of general function similarity relations. Behavioral data suggest the involvement of distinct cognitive mechanisms in manipulable artifact object semantic processing. The aim of the present study was to assess the neural correlates of thematic, and specific and general function similarity relation processing. Specifically, we investigated whether time course differences between semantic relations could be highlighted at the neurophysiological level. We used a protocol combining semantic priming with electroencephalography, and manipulated the type of semantic relation and the duration of the interval between prime and target objects. Two consistent and complementary results were shown. On N1 and P3 components, semantic priming was observed for thematic relations only. On N400 component, the type of semantic relation interacted with interval duration, and semantic priming was visible for all 3 relations after the longest interval only. Results revealed graded processing time courses for thematic, specific function similarity, and general function similarity relations at the neural level, and further indicate that thematic relations impact object processing during the early stages of object recognition. Findings suggest a hierarchical organization of three types of semantic relations based on functional knowledge. The parallel between semantic relations involving manipulable artifact objects and levels of action representations is discussed.