@mattbrowne, thank you for the link. I had not heard the term ‘veto power’ although I have long considered an existence of free-won’t as a conjunct of freewill. However, as the references (I love wikipedia) that @ETpro provided posits, it (veto power) ain’t necessarily so.
Wikipedia’s “Neuroscience of free will” reports that ”[r]ecent research by Simone Kühn and Marcel Brass suggests that our consciousness may not be what causes some actions to be vetoed at the last moment. . . . the phenomenon of ‘consciousness’ is more of narration than direct arbitration (i.e. unconscious processing causes all thoughts, and these thoughts are again processed subconsciously).”
It may be that “the decision to ‘veto’ an action is determined subconsciously, just as the initiation of the action may have been subconscious in the first place.” [Consciousness and Cognition Volume 18, Issue 1, March 2009, Pages 12–21] (wikipedia’s reference)
@ETpro, the above quotations question, if not refutes, your contention that a purpose of the prefrontal cortex is to choose not to act. I think that in a sense it does, just as in the same sense it chooses to act. Both choices arise from the ability of the prefrontal cortex to envision a desirable or undesirable future reality, and to conceive of how this future may be realized.