What can we learn from T2* maps of the cortex?

Studies have shown that T2* contrast can reveal features of cortical anatomy. However, understanding the relationship between T2* contrast and the underlying cyto- and myelo-architecture is not an easy task, given the number of confounds, such as myelin, iron, blood vessels and structure orientation. Moreover, it is difficult to obtain reliable T2* measurements in the cortex due to its thin and folded geometry and the presence of artifacts. This review addresses issues associated with T2* mapping in the human cortex. After describing the theory behind T2* relaxation, a list of practical steps is proposed to reliably acquire and process T2* data and then map these values within the cortex using surface-based analysis. The last section addresses the question: "What can we gain from T2* cortical mapping?", with particular emphasis on Brodmann mapping.