The neural substrate of the ideomotor principle: an event-related fMRI analysis

The present fMRI study sought to investigate the neural basis of perceiving learned action effects and thereby to test for hypotheses based on the ideomotor principle. For this purpose, we had subjects undergo a two-phase experimental procedure comprising an acquisition and a test phase, the latter administered inside the MR scanner. During the acquisition phase, free-choice button presses were contingently followed by one of two tones of different pitch which thereby should become "learned action effects". During the following test phase, subjects were presented with the action effects either when in a passive (non-acting) state or when they carried out forced-choice button presses. Conform to our expectations, we found evidence for a motor effector activation following the passive perception of effect tones which elicited activation in the neural motor system (premotor and somatosensory cortices, SMA, and cerebellum). Surprisingly, however, this activation was observed for left-hand effect tones only, suggesting a basic asymmetry in the impact of ideomotor learning. Moreover, we found activation in the posterior prefrontal and temporo-parietal cortex in response to action effects during the pursuit of goal-directed action. This suggests that action effects attracted special attention and thereby engaged selective cognitive control processes to ensure task-appropriate performance. Finally, there was reduced premotor activation for response-compatible as compared to response-incompatible action effects which can be taken as indication for differential requirements on the motor system and thus for behavioral interference and/or facilitation by learned action effects.