Visual and visuocognitive development of children born very prematurely

Abstract

Visual development provides a set of milestones and sensitive methods for assessing brain development in infancy. In particular the first months of post-term life see the emergence of visual cortical function. Measures of subcortical and cortical function have led us to a detailed neurobiological model of normal visual development which gives a basis for assessing visual development in very premature infants. This chapter reviews the ocular and cerebral factors associated with preterm birth (at 32 weeks gestation or earlier) which may impair development and presents the behavioural and electrophysiological methods now available (including 'fixation shifts' for gauging visual attention and specific visual event-related potentials (VERP)) which allow assessment of the impact of these factors on development and the prediction of likely later neurocognitive deficits. Studies are reviewed which show that in the first year of post-term life, visual cortical development in healthy preterm-born infants is generally similar to term-born infants matched for post-term age, although there is some small relative delay in the development of motion processing in the first few months of life. However, infants in whom neonatal MRI reveals cerebral damage, in particular white matter abnormality, show deficits in visual and visuocognitive development that are graded according to the severity of the damage. These deficits are also predictive of later neurocognitive status. In the preschool years, visuocognitive functions show the impact of preterm birth. By age 6, the preterm group as a whole show selective deficits in visuomotor functions, attention, including executive control, and other aspects of spatial cognition. These deficits are primarily associated with the dorsal stream of visual, spatial, and visuomotor processing controlling actions. These dorsal stream networks are linked to and overlap with those underpinning different components of attention. However, this 'vulnerability' of the dorsal system is not unique to children born very preterm; it is also a feature of many neurodevelopmental disorders, e.g. autism,Williams syndrome, Fragile X, and children with congenital cataract. The main challenge for the future is to use these new measures and technologies, developed as child-friendly methods for successful assessment of developmental progress in early life, in early trials of intervention. Such early measures should, in the long term, help preterm infants develop cognitive abilities that allow them to reach their true intellectual and social potential.