Mapping the Human Cortical Surface by Combining Quantitative T(1) with Retinotopy(†)

We combined quantitative relaxation rate (R(1)= 1/T(1)) mapping—to measure local myelination—with fMRI-based retinotopy. Gray–white and pial surfaces were reconstructed and used to sample R(1) at different cortical depths. Like myelination, R(1) decreased from deeper to superficial layers. R(1) decreased passing from V1 and MT, to immediately surrounding areas, then to the angular gyrus. High R(1) was correlated across the cortex with convex local curvature so the data was first “de-curved”. By overlaying R(1) and retinotopic maps, we found that many visual area borders were associated with significant R(1) increases including V1, V3A, MT, V6, V6A, V8/VO1, FST, and VIP. Surprisingly, retinotopic MT occupied only the posterior portion of an oval-shaped lateral occipital R(1) maximum. R(1) maps were reproducible within individuals and comparable between subjects without intensity normalization, enabling multi-center studies of development, aging, and disease progression, and structure/function mapping in other modalities.