Locating ‘dorsal stream vulnerability': high-density global motion and form coherence VEPs related to MRI in infants born very preterm

Abstract

In typical development, infants' global motion responses are located more laterally (MT?) compared to the dominant occipital midline focus in adults, indicating developmental reorganization of cortical motion networks (Wattam-Bell et al, Current Biol, 2010). In infants born very preterm (≥32 weeks gestational age), VERP and behavioural visual cortical indicators (orientation selectivity and attention shifts) correlate with structural MRI measures of brain damage and predict later neurocognitive outcome (Atkinson et al, Arch Dis Child 2008). In later childhood, functions associated with the dorsal stream (e.g. motion coherence thresholds) are particularly vulnerable in preterms and children with specific neurodevelopmental disorders e.g. Williams syndrome, autism (Atkinson & Braddick, Prog Brain Res 2007; Braddick et al, Neuropsychologia, 2003).

Here we study form and motion responses in preterm infants (N = 22) at 5 months post-term age. Activation by global form and motion coherence (taken as signatures of extra-striate ventral- and dorsal-stream areas) was mapped using a high-density geodesic sensor array, and compared with detailed analysis of term-equivalent- MRI, scoring 20 identifiable anatomical markers for abnormality (e.g optic tract, putamen, extrastriate, occipito-parietal) alongside behavioural tests of acuity, binocularity, fields, accommodation, attention shifts. Preterm infants with MRI scores indicating severe brain damage (e.g cystic PVL) showed absent or poor global motion responses compared to either global form or local contrast. Those with mild/moderate MRI scores (e.g. no optic tract damage but minor extrastriate abnormality) showed reliable global motion responses, but with a more immature distribution, showing isolated lateral foci of activation compared to term-born controls.

We conclude that, in line with evidence in later childhood for ‘dorsal stream vulnerability', perinatal risk factors affect global motion responses in infancy more than static form. Even relatively healthy preterm infants (mild/moderate group) show immaturity in the developmental reorganization of cortical motion areas, which may be an early signature of a developmental motion processing deficit.

Medical Research Council, the Garfield Weston Foundation, and Wellbeing NIHR Biomedical Research Centre funding scheme.