Abstract
The frontal pole corresponds to Brodmann area (BA) 10, the largest single architectonic area in the human frontal lobe. Generally, BA10 is thought to contain two or three subregions that subserve broad functions such as multitasking, social cognition, attention, and episodic memory. However, there is a substantial debate about the functional and structural heterogeneity of this large frontal region. Previous connectivity-based parcellation studies have identified two or three subregions in the human frontal pole. Here, we used diffusion tensor imaging to assess structural connectivity of BA10 in 35 healthy subjects and delineated subregions based on this connectivity. This allowed us to determine the correspondence of structurally based subregions with the scheme previously defined functionally. Three subregions could be defined in each subject. However, these three subregions were not spatially consistent between subjects. Therefore, we accepted a solution with two subregions that encompassed the lateral and medial frontal pole. We then examined resting-state functional connectivity of the two subregions and found significant differences between their connectivities. The medial cluster was connected to nodes of the default-mode network, which is implicated in internally focused, self-related thought, and social cognition. The lateral cluster was connected to nodes of the executive control network, associated with directed attention and working memory. These findings support the concept that there are two major anatomical subregions of the frontal pole related to differences in functional connectivity.Electronic supplementary materialThe online version of this article (doi:10.1007/s00429-014-0809-6) contains supplementary material, which is available to authorized users.
Highlights
The most anterior portion of the primate brain is often designated as a single brain region of granular cortex, broadly defined as Brodmann area (BA) 10 in humans [and BA 12 in non-human primates, later reclassified as BA 10 by Walker (1940)], or the frontal polar cortex (FPC) (Fig. 1) (Barbas and Pandya 1989; Petrides et al 2012).T
The first aim of this study was to parcellate the human frontal polar cortex into distinct subregions based on their structural white matter connectivity, using probabilistic tractography
We performed the clustering algorithm on the FPC with an increasing number of clusters (2, 3, and 4) and determined the largest value for K where the clusters remained consistent amongst all 35 subjects (Beckmann et al 2009; Mars et al 2011, 2012)
Summary
The most anterior portion of the primate brain is often designated as a single brain region of granular cortex, broadly defined as Brodmann area (BA) 10 in humans [and BA 12 in non-human primates, later reclassified as BA 10 by Walker (1940)], or the frontal polar cortex (FPC) (Fig. 1) (Barbas and Pandya 1989; Petrides et al 2012). Downar Department of Psychiatry, University Health Network, Toronto M5T 2S8, Canada
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