Neural Mechanisms of Self-Generated Action Sequences.

Complex problems often allow multiple paths to a solution. Choosing and taking the best path is an important part of the executive cognition that underpins intelligent problem-solving behavior. However, once a path is chosen, the motor system must be activated for executing it. This interface between problem-solving and self-generated action has rarely been studied. We recorded EEG movement-related potentials while 25 participants (7 males, 18 females) performed the "Tower of London" problem-solving task. In a control condition, participants merely followed instructed steps without planning for any goal and thus without any sense that their movements solved a problem. Readiness potentials (RPs) preceding actions showed a more sustained preparatory negativity for self-generated than stimulus-driven movements. Critically, this effect was most pronounced at the first move of a sequence and diminished at later stages, indicating that preparatory activity is closely linked to the planning demands of sequence initiation. Consistent with this, contralateral motor β-band suppression was stronger for self-generated actions, particularly at sequence onset, but remained present across all moves, indicating that it is not selectively modulated by sequence position in the same way as the RP. Multivariate pattern analysis further showed that self-generated and stimulus-driven actions could be reliably distinguished throughout the entire preparatory period. Taken together, these results show a deep interaction between executive function and self-generated actions and draw attention to the fact that, if a problem can be solved, then actually solving it generally requires executive cognition to trigger self-generated actions, based on a plan.