John Duncan & Adrian M. Owen 
Executive Control and the Frontal Lobe: Current Issues [PDF ebook] 

While the importance of the prefrontal cortex for "higher-order" cognitive functions is largely undisputed, no consensus has been reached regarding precise specifications of these functions. For example, although some degree of regional specialization within the frontal lobe seems inevitable, by and large, most attempts to map specific cognitive functions onto neuroanatomical and/or cytoarchitectonic subdivisions have been disappointing. Although a high degree of functional specialization probably exists within the frontal cortex, it seems increasingly likely that the structural organization of this system does not relate, in any straightforward way, to contemporary models of cognition.