Individuals born with congenital cataracts exhibit both persisting impairment and considerable recovery of white matter microstructure after sight restoration

IntroductionIndividuals born with dense bilateral cataracts, for whom sight was restored later in life (congenital cataract reversal individuals), provide a unique opportunity to explore the impact of early (visual) experience on the development of the human brain. MethodsUsing diffusion MRI we assessed white matter microstructure in a sample of 20 congenital cataract reversal individuals using along-the-tract analysis of major visual white matter tracts and non-visual control tracts. We additionally recruited three control groups: 8 permanently congenitally blind individuals, 11 individuals with reversed later-onset cataracts (developmental cataract reversal individuals), and 24 age- and sex-matched typically sighted controls. ResultsDiffusion tensor metrics exhibited significant group differences which were specific to visual tracts. Compared to normally sighted controls, congenitally blind and congenital cataract reversal individuals both showed impaired white matter integrity. However, differences were much more spatially extensive for permanently congenitally blind individuals, and a direct comparison revealed relatively higher tract integrity for congenital cataract reversal individuals, suggesting a high degree of recovery following sight restoration. DiscussionThe present pattern of results is compatible with the idea of both a sensitive period for white matter development and significant white matter plasticity later in life. We propose that group differences are largely driven by differences in myelination. Thus, the considerable recovery in congenital cataract reversal individuals would suggest that life-long myelin plasticity may remain higher than neuronal structural plasticity.