A proposal for MRI-based parcellation of the frontal pole

The frontal pole (FP), which largely overlaps with Brodmann's area (BA) 10, is the rostral-most part of the hominid cerebral cortex, and plays a critical role in complex aspects of human cognition. The existing conventions suggested for MRI-based parcellation of this important frontal subdivision have limited cytoarchitectonic meaning with regard to the demarcation of the FP from adjacent prefrontal subdivisions. In this paper, we propose the coronal section containing the anterior termination of the olfactory sulcus (ATOS) as an easy-to-identify landmark for FP parcellation that largely overlaps with the cytoarchitectonic distinction between BA 10 and the more posterior cytoarchitectonic subdivisions of the PFC. Manual segmentation-based parcellation of the FP using the proposed landmark in 20 healthy volunteers yielded highly reliable (standardized item alpha = 0.92) volumetric estimates [right FP volume = 8.421 cm3 (SE = 0.773, range 3.107-15.741); left FP volume = 8.039 cm3 (SE = 0.708, range 2.234-12.956)]. The volumetric measurements of right FP generated in the present study were comparable to those reported in a prior study of BA 10 using histological sections and stereological techniques (Semendeferi et al. In: Am J Phys Anthropol 114:224-241, 2001). Therefore, in the absence of a naturally occurring sulcal boundary, the proposed method for parcellation of the FP can provide unbiased volume estimations for studies of healthy and disordered populations of subjects.