Brain structure changes visualized in early- and late-onset blind subjects

Abstract

We examine 3D patterns of volume differences in the brain associated with blindness, in subjects grouped according to early and late onset. Using tensor-based morphometry, we map volume reductions and gains in 16 early-onset (EB) and 16 late-onset (LB) blind adults (onset <5 and >14 years old, respectively) relative to 16 matched sighted controls. Each subject’s structural MRI was fluidly registered to a common template. Anatomical differences between groups were mapped based on statistical analysis of the resulting deformation fields revealing profound deficits in primary and secondary visual cortices for both blind groups. Regions outside the occipital lobe showed significant hypertrophy, suggesting widespread compensatory adaptations. EBs but not LBs showed deficits in the splenium and hypertrophy in the isthmus. Gains in the isthmus and non-occipital white matter were more widespread in the EBs. These differences may reflect regional alterations in late neurodevelopmental processes, such as myelination, that continue into adulthood.

Impact of Early and Late Visual Deprivation on the Structure of the Corpus Callosum: A Study Combining Thickness Profile with Surface Tensor-Based Morphometry

“…With group difference analysis, our results confirm and extend prior works by demonstrating how blindness acquired at different periods during development influence the structural reorganization of the CC (e.g. Leporé et al (2010)). …”

“…Prior 2D TBM analyses of the corpus callosum (Leporé et al 2010) revealed reductions in the isthmus and splenium of the corpus callosum in early but not late blind subjects when compared to sighted controls. Direct comparisons of the early and late blind groups did not find any significant changes, leaving open the question of how the period of visual deprivation impacts the structure of the CC.…”

“…The corpus callosum (CC) is a particularly interesting subcortical structure to study in blind individuals (Leporé et al 2010; Bock et al 2013). The CC is the largest fiber bundle in the brain and establishes connections between the hemispheres, and predominantly, but not solely, between the cortical areas (Caleo et al 2013).…”

“…However, how visual deprivation affects the structure of the corpus callosum is still a matter of debate. Some studies suggest that early acquired blindness leads to a reduction in splenial white matter volume (Leporé et al 2010; Levin et al 2010; Shimony et al 2006). However, Bridge et al (2009) did not find any structural differences within the splenium of anophthalmic subjects.…”

Spatial Updating Depends on Gaze Direction Even after Loss of Vision

“…Moreover, corpus callosum areas substantially increase from ages 4 to 18 years (Giedd et al, 1996), which facilitates interhemispheric transfer and thus might enhance spatial remapping (cf., Berman et al, 2005). As a consequence, a lack of vision during that specific time may influence the development of the corpus callosum, since congenitally blind compared with sighted and late blind people show a reduced volume of a callosal region that primarily connects visual-spatial areas in the PPC (Leporé et al, 2010). Such changes in the structural and functional organization of the brain during childhood might trigger the switch from internal to external spatial coding strategies.…”