An integrated model of prefrontal cortex processing. Neurocognitive mechanisms underlying prefrontal cortex processing in human behavior

An integrative, theoretical, interdisciplinary approach is adopted to understand prefrontal cortex processing. This approach can provide a solution to specific problems posed by neuropsychology, cognitive psychology, cognitive neuropsychology, cognitive neuroscience, neurophysiology and neurophilosophy. Several theories of prefrontal cortex processing are reviewed. These theories are either too general or too narrow. They are all developed empirically and suffer from biases of both subjects and procedure selection. Goldman-Rakic's (1987a) cognitive/behavioral explanation for the prefrontal cortex processing provides a comprehensive analysis of the neuroanatomy and the neurophysiology of the prefrontal cortex. Norman and Shallice (1986) developed a cognitive theoretical point of view, which was later applied to the prefrontal cortex. The integrated model uses the neurophysiological analysis of Goldman-Rakic with data from PET studies. Several principles of the cognitive aspects of the integrated model are adopted from the model of Norman and Shallice. Only those elements that can be explained by neural mechanisms are incorporated. The integrated model perceives the human being as an active self-regulative organism who participates in constant interaction and transaction with the environment. In routine behavior, schemas elicit an automatic response without the need for further attentional/conscious recourses of the prefrontal cortex. When the automatic process fails, further attentional recourses, mediated by the prefrontal cortex, are needed. The integrated model suggests five neurocognitive mechanisms underlying this process, including an emotional/motivational network that mediates prefrontal control over emotional effects. The five networks connect the prefrontal cortex to other regions in the brain. These networks work together, in parallel, affecting different aspects of schemas at the same time. The integrated model can better explain behaviors in normal and disturbed subjects. ADHD, which recently was considered as a prefrontal disorder, is explained by different disturbances in the five neurocognitive networks suggested by the integrated model. The specification of mechanisms, provided by the model, goes further ahead than other suggested general accounts that underlie prefrontal disorder in ADHD.