The prefrontal cortex in the neurology clinic.

Throughout the nervous system, posterior structures are mainly devoted to receptive functions-sensation and perception-while anterior structures are devoted to motor functions. In the cortex, that dichotomy is unclear because perception and action are intertwined in the perception-action cycle, the biocybernetic cycle that adapts the organism to its environment. All neural systems store information (memory), which they enact in behavior and language. There are no "systems of memory" but the memory of systems. The cortex of the frontal lobe is a hierarchical system: motor cortex at the bottom for coordination of simple movements, and prefrontal cortex at the top for complex goal-directed actions. In the coordination of such actions, the frontal hierarchy engages the posterior (perceptual) cortex in the perception-action cycle. Inputs to the cycle come to prefrontal cortex from sensory-evoked perceptual memory and biologic (phyletic) memory. The first comes from neocortex, the second from limbic structures-through orbitomedial cortex. Outputs flow to pyramidal and diencephalic structures. Feedback inputs for monitoring and correction operate at all levels of the cycle. All prefrontal functions-planning, executive attention, working memory, decision-making, and inhibitory controls-are prospective, i.e., have a future perspective for the cycle to reach its goal. Damage to lateral prefrontal cortex impairs all of them. Orbitofrontal damage impairs the exclusionary aspect of attention and often leads to poor impulse control, excessive risk taking, unstable mood, and antisocial behavior. Medial prefrontal damage leads to poor monitoring of behavioral outcome for prevention of errors.