Congruent action context releases Mu rhythm desynchronization when visual objects activate competing action representations.

Recent findings demonstrated that object perception is affected by the competition between action representations. Simultaneous activation of distinct structural ("grasp-to-move") and functional ("grasp-to-use") action representations slows down perceptual judgements on objects. At the brain level, competition reduces motor resonance effects during manipulable object perception, reflected by an extinction of µ rhythm desynchronization. However, how this competition is solved in the absence of object-directed action remains unclear. The present study investigates the role of context in the resolution of the competition between conflicting action representations during mere object perception. To this aim, thirty-eight volunteers were instructed to perform a reachability judgment task on 3D objects presented at different distances in a virtual environment. Objects were conflictual objects associated with distinct structural and functional action representations. Verbs were used to provide a neutral or congruent action context prior or after object presentation. Neurophysiological correlates of the competition between action representation were recorded using EEG. The main result showed a release of µ rhythm desynchronization when reachable conflictual objects were presented with a congruent action context. Context influenced µ rhythm desynchronization when the action context was provided prior or after object presentation in a time-window compatible with object-context integration (around 1000 ms after the presentation of the first stimulus). These findings revealed that action context biases competition between co-activated action representations during mere object perception and demonstrated that µ rhythm desynchronization may be an index of activation but also competition between action representations in perception.

Do manufactured and natural objects evoke similar motor information? The case of action priming.

There is considerable evidence that visually presented manipulable objects evoke motor information, supporting the existence of affordance effects during object perception. However, most arguments come from stimulus-response compatibility paradigms, raising the issue of the automaticity of affordance effects. Action priming paradigms overcome this issue but show less reliable results, possibly because affordance effects are moderated by additional factors. The present study aimed to assess whether affordance effects highlighted in action priming paradigms could be affected by object category (manufactured or natural). A total of 24 young adults performed a semantic categorisation task on natural and manufactured target objects presented after neutral (non-grasping hand postures) or action (congruent power or precision grips) primes. Results revealed a modulation of action priming effects as a function of object category. Object semantic categorisation was faster after action than neutral primes, but only for manufactured objects. Results suggest that natural and manufactured objects evoke distinct types of affordances and that action priming paradigms favour the evocation of functional affordances during object semantic categorisation. This finding fuels the debate on the nature of the motor information evoked by visual objects.