How Visual Experience Alters Cortical Myelination of The Visual Cortex: Insights From Combined 3T And 7T MRI Studies

How does sensory experience shape the fine-grained structure of brain regions? Investigating how regions typically supporting vision reorganize their circuits in congenitally blind individuals provides compelling information on the role sensory experience plays in shaping brain structures. Here, we combine two MRI datasets acquired at 3T and 7T in congenitally blind and matched sighted subjects to map cortical tissue properties using T1w/T2w ratio at the whole-brain level (3T) and quantitative T1 relaxation at the layer level in the occipitotemporal cortex (7T). We show that blindness triggers a significant reduction in myelination throughout the occipitotemporal cortex. Despite this global reduction in myelin content, our 7T data reveal that the layer distribution and the gradient across regions in myelin content are preserved in blind people. These results show that while the ‘global’ cortical myelin might be impacted by the lack of visual experience during development, ‘local’ gradients within and across regions are retained, suggesting an interplay between hard-coded and plastic aspects of human brain structure.