The Prefrontal Cortex—An Update Time Is of the Essence

many of the principles discussed below apply also to the PFC of nonprimate species. according to the cytoarchitectonic map of Brodmann The physiology of the cerebral cortex is organized in (1909), recently updated for the monkey by Petrides and hierarchical manner. At the bottom of the cortical organi-Pandya (Figure 1). Phylogenetically, it is one of the latest zation, sensory and motor areas support specific sen-cortices to develop, having attained maximum relative sory and motor functions. Progressively higher areas—of growth in the human brain (Brodmann, 1912; Jerison, later phylogenetic and ontogenetic development—support 1994), where it constitutes nearly one-third of the neocor-functions that are progressively more integrative. The tex. Furthermore, the PFC undergoes late development in prefrontal cortex (PFC) constitutes the highest level of the course of ontogeny. In the human, by myelogenic and the cortical hierarchy dedicated to the representation synaptogenic criteria, the PFC is clearly late-maturing and execution of actions. The PFC can be subdivided in three major regions: Huttenlocher and Dabholkar, 1997). In the monkey's orbital, medial, and lateral. The orbital and medial re-PFC, myelogenesis also seems to develop late (Gibson, gions are involved in emotional behavior. The lateral 1991). However, the assumption that the synaptic struc-region, which is maximally developed in the human, pro-ture of the PFC lags behind that of other neocortical vides the cognitive support to the temporal organization areas has been challenged with morphometric data of behavior, speech, and reasoning. This function of (Bourgeois et al., 1994). In any case, imaging studies temporal organization is served by several subordinate indicate that, in the human, prefrontal areas do not attain functions that are closely intertwined (e.g., temporal in-full maturity until adolescence (Chugani et al. ization can be discerned in the PFC is not so much is consistent with the behavioral evidence that these attributable to the topographical distribution of those areas are critical for those higher cognitive functions functions as to the nature of the cognitive information that develop late, such as propositional speech and with which they operate. Much of the prevalent confu-reasoning. sion in the PFC literature derives from two common The profuse variety of connections of the PFC is obvi-errors. The first is to argue for one particular prefrontal function while opposing or neglecting others that complement it; the second is to localize any of them within a discrete portion of PFC. The functions of the PFC rely closely on its connections with …