Planning appropriate forthcoming actions rather than responding to sensory stimuli in a reflexive manner is characteristic of human behavior and relies on the functions on the frontal lobes. Dorsolateral areas of the prefrontal cortex are thought to be involved in the so-called "executive functions' that subserve the mental preparation of future actions. These executive functions require elementary processes that are generally gathered within the framework of working memory, i.e., the short-term maintenance of relevant information for the forthcoming action, the mental manipulation of this information, the allocation of the attentional resources and the mental preparation of the sequence of actions. These processes are required for elaboration of adequate behavioral responses or cognitive sets. The prefrontal cortex also provides an inhibitory control on the automatic activation of more basic behaviors induced by sensory and environmental stimulations. According to this view, there is a dynamic interaction between frontal and parietal activation of behavioral sets that depends on contextual parameters. The prefrontal cortex is involved in the meaning of events and external stimuli. This allows the elaboration of goal-directed behaviors which result from a multistep, computational and explicit process, organized within the dorsolateral part of the prefrontal cortex. The latter is the only cortical region which receives sensory messages from external world (via associative sensory areas) and internal milieu. Therefore, the prefrontal cortex is able to hold the internal representations of the outside world or from the past in short-term memory and to manipulate this information to provide behavior based on ideas and thoughts rather than immediate stimuli. In other words, working memory could be seen as a buffer space between perception and action that integrates the incoming information to elaborate the future action schemas. Goal-directed behaviors can therefore be elaborated that integrate both the subject's own needs and information from the external world to maintain internal balance and to adapt to environmental contingencies. Alternatively, action can be elicited by implicit and automatic routes in response to the reinforcement-related value of a stimulus. These routes involve the amygdala (for stimulus-reinforcement association learning), the orbitofrontal cortex (for rapid updating) and the basal ganglia (for response activation).
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