17 Rostral Prefrontal Brain Regions (Area 10): A Gateway between Inner Thought and the External World?

17.1 Introduction This chapter reviews recent evidence from our laboratory (and others) that suggests that the most anterior parts of the frontal lobes of the brain support cognitive processes which are critical to complex volitional behavior in humans. We conclude by proposing a simple preliminary hypothesis about the role of this region in cognition. The part of the frontal lobes that is foremost in the brain has many names. The most common of these are " anterior prefrontal cortex, " " the frontal pole, " " frontopolar cortex, " and " rostral prefrontal cortex " (rostral PFC). Of these, we favor the use of the term " rostral " since the term is equivalent to others that are used to denote regions of the brain (e.g., caudal, dorsal, lateral, medial, ventral). However, these terms all refer to a region which broadly corresponds to the cytoarchitectonic area known as Brodmann Area (BA) 10. There is very good reason for suspecting that this brain region plays a critical role in human cognition. For instance, it is large in humans: in volu-metric terms probably the largest single architectonic region of the frontal lobes (Christoff et al. 2001), which themselves account for approximately 30 percent of the total cortical surface. Given that the brain may consume as much as 20 percent of the oxygen we extract from the air that we breathe (Raichle et al. 2001), there must be some evolutionary advantage to such a large brain region. Moreover, the rostral PFC regions are of unique proportional size in humans; they are for instance double the relative size in humans compared with chimpanzees (Semendeferi et al. 2001). And finally, this region is possibly the last to achieve myelination, and it has been argued that tardily myelinating areas engage in complex functions highly related to the organ-ism's experience (Fuster 1997, p. 37). These are all good reasons to imagine that the rostral PFC may support cognitive processing which is especially important to humans.