Drs. Buchanan and Pearlson Reply

To the Editor: Dr. Green correctly notes that there are a number of differences between our definition of the heteromodal cortex and the one provided by Mesulam in his textbook (his reference 2). We asserted that our definition was primarily based on the definition provided by Mesulam, but we agree that the use of the word “primarily” does not provide an accurate accounting of the noted differences between the two definitions, nor does it reflect accurately how we modified the Mesulam definition in our other written descriptions of the heteromodal association cortex (1). In particular, we attempted to refine the concept based on the work of Goldman-Rakic and colleagues, who conducted a series of studies demonstrating the intimate, reciprocal structural connections between the prefrontal cortex, the inferior parietal cortex, and the superior temporal gyrus (reviewed in reference 1). These considerations have led us and other researchers to adopt a more conservative definition of the heteromodal cortex (2, 3). In addition, we would argue that the faceplate (Dr. Green’s reference 2) underestimates the extent of the involvement of the superior temporal gyrus in the heteromodal cortex, as reviewed by one of us (4).

Dr. Green also observes that our definition of the prefrontal cortex includes the premotor cortex. In a previous article (5), we acknowledged the point that there is no reliable sulcal boundary between the premotor cortex and the prefrontal cortex and that our definition of the superior and middle prefrontal regions includes the supplementary motor area and the premotor cortex, respectively. We did not reiterate this point in the current article. We thank Dr. Green for giving us an opportunity to clarify these issues.