Phase maps reveal cortical architecture

Abstract

In this issue of PNAS, Duyn et al. (1) present a magnetic resonance imaging (MRI) technique that reveals astonishing and hitherto unseen details of the architecture of the cerebral cortex of living human beings. The cortex (Latin for “bark” or “outer rind”) is a thin layer of gray matter that is highly folded to attain a large surface area within the limited volume of the human skull, and it is thought to be the substrate for the vast majority of the cognitive skills that we possess. That the cortex has an interesting laminar structure, and that this structure may relate to its functional properties, has been known for more than 100 years (2, 3). Directly visualizing these laminar properties in living humans is one of the central goals of structural neuroimaging research. From a neuroscience standpoint, the importance of imaging cortical architecture stems from the fact that the human cortex can be parcellated into discrete regions based on changes in the laminar distributions of cell types and density, dating back to the classic work of Korbinian Brodmann a century ago, one of a number of famous cortical parcellations (3–7). These regions, frequently referred to as “cortical areas,” are strongly tied to the functional properties of the brain, and hence being able to robustly and routinely delineate them in vivo would be a fundamental tool in research aimed at deepening our understanding of the human brain.