Morphometry of the corpus callosum

The corpus callosum is the largest commissure in the human brain and the principal connection transmitting information between the two hemispheres. Importantly, midsagittal callosal size scales with the number of small diameter fibers crossing through, suggesting that a larger corpus callosum relays more connections between the hemispheres than a small one. Moreover, fibers of the corpus callosum are arranged following a specific organization implying that regional callosal size is functionally significant. This has sparked considerable interest in the neuroscience community to develop and refine approaches to analyze callosal morphology not only in terms of its overall size but also with respect to its local dimensions. In this chapter, we first briefly review traditional parcellation schemes allowing for local measures of callosal morphology. Subsequently, we detail a newer computational technique, commonly referred to as “callosal thickness” approach, measuring callosal distances at 100 equally spaced nodes. To demonstrate an application of this approach, we examined callosal thickness in relation to chronological age in 72 healthy subjects (36 men, 36 women) aged between 30 and 69 years. The chapter then progresses by summarizing advantages and potential drawbacks of this approach and concludes with practical tips and helpful pointers for conducting a callosal thickness analysis.