Does a defendant knowingly, voluntarily, and intelligently enter into a plea agreement where he is neurologically incapable of understanding the future consequences of that agreement?

QUESTION PRESENTED Does a defendant knowingly, voluntarily, and intelligently enter into a plea agreement where he is neurologically incapable of understanding the future consequences of that agreement? Correspondingly, is a court’s determination of "knowing" and "intelligent" dependent on what the defendant was told or what the defendant had the ability to understand?