ReviewMonitoring and Control of Action by the Frontal Lobes

receipt of rewarding stimuli, whereas a negative evaluation would include either omission of an expected reward or delivery of an aversive stimulus (Rolls, 1999). Sensitivity to reinforcement allows an organism to act in accordance with regularities in the environment. This Success requires deciding among alternatives, con-sensitivity can be expressed through mechanisms intrin-trolling the initiation of movements, and judging the sic to sensorimotor neural systems. Intrinsic means of consequences of actions. When alternatives are diffi-adapting to regularities in the environment include prim-cult to distinguish, habitual responses must be over-ing in the sensory and motor neural pathways that bias come, or consequences are uncertain, deliberation is for or against repeated responses. For example, the necessary and a supervisory system exerts control response times of macaque monkeys producing eye over the processes that produce sensory-guided movements to visual stimuli vary as movements are re-movements. We have investigated these processes by peated or alternate, and this sequentially ordered perfor-recording neural activity in the frontal lobe of macaque mance is associated with changes in the neural activity monkeys performing a countermanding task. Distinct in the superior colliculus (Dorris et al., 2000) and frontal neurons in the frontal eye field respond to visual stimuli eye field (Bichot and Schall, 2002). However, such mech-or control the production of the movements. In the anisms seem insufficient to contend with more complex supplementary eye field and anterior cingulate cortex, contingencies. When the environment is ambiguous or neurons appear not to control directly movement initi-presents competing demands, or the mapping of stimu-ation but instead signal the production of errors, the lus onto response is complex or contrary to habit making anticipation and delivery of reinforcement, and the performance prone to errors, then an executive, supervi-presence of processing conflict. These signals form sory system exerts control. Supervisory, executive con-the core of current models of supervisory control of trol over the perception, selection, and production sys-sensorimotor processes. tems is seen as a central component of human cognition A central goal of neuroscience is to explain how behavior 1996; Logan and Gordon, 2001). and psychological processes come from neural mecha-These questions have been investigated effectively nisms. This problem is particularly acute when it involves with visually guided eye movements. The neural repre-decision making for voluntary behavior because the sentation of visual stimuli is very well understood (e.g., stakes are no less than understanding the physical basis Parker and Newsome, 1998) and the processes …