The foveal and peripheral visual pathways have very different biological properties. For a study, researchers used diffusion MRI (dMRI) to examine the tissue characteristics of optic radiations (OR) that transport foveal and peripheral information to the primary visual cortex (V1). The Human Connectome Project (HCP; n=180; age 22-35) and the UK Biobank (UKB; n=7,088; age 45-81) were used to study dMRI. OR was identified in the HCP using a three-dimensional atlas, with OR sections representing the fovea and periphery being split based on V1 fMRI responses around OR endpoints. The UKB used landmarks to define OR and split it using anatomically-based estimations of V1 responses near OR endpoints. A kurtosis model was used to model the dMRI signal, which offers information regarding tissue microstructure. Despite differences in data collection, population characteristics, and analysis methods, both datasets revealed that the foveal OR had higher fractional anisotropy, lower mean diffusivity, and higher mean kurtosis than the peripheral OR, which is consistent with denser nerve fiber populations in foveal pathways. Investigators discovered that age was linked with increasing diffusivity and reduced anisotropy and kurtosis in the UKB, consistent with decreasing density and tissue organization with aging. However, anisotropy in the fovea diminished quicker than in the periphery, whereas diffusivity rose faster in the periphery, implying that foveal and peripheral OR mature differently.
Reference:jov.arvojournals.org/article.aspx?articleid=2778467
