Revisiting Free Will: Distributed Activity in the Medial Frontal Cortex Predicts Self-Initiated Action
Research indicates that significant damage to primates' medial frontal cortex (MFC) can impede action initiation when anticipating rewards. However, the specific roles within the MFC related to self-generated action preparation remain debated. Here, while two macaques were engaged in an oculomotor task, they occasionally paused and self-resumed the task after varying amounts of time. We utilized the high signal-to-noise ratio from spatial changes in cerebrovascular blood volume (CBV) recorded with ultrafast ultrasound imaging (fUSi) to determine whether the intervals of breaks or the resumption of task-related CBV signals could predict the execution of an ongoing single action. We show that self-initiated eye movements activate the Supplementary eye field (SEF) and the midcingulate cortex (MCC) up to 5.5 seconds before movement execution. Importantly, our results show that a concurrent activity in the SEF and MCC predicts how these two regions might simultaneously exert opposing influences on the voluntary pause and resume of tasks on a single trial basis. The quantification of this dynamic interaction is a novel step for understanding voluntary action in primates and its ability to initiate one's movement based on internal motivations rather than driven instructed behavior.