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Periventricular brain injury, visual motion processing, and reading and spelling abilities in children who were
Andrea L S Downie1, Lorna S Jakobson, Virginia Frisk
1Department of Psychology, The Hospital for Sick Children, Toronto, Ontario, Canada.
Insights
Extremely low birthweight (ELBW) children show significant visual motion processing deficits, independent of brain injury or reading difficulties. These visual impairments correlate with lower Performance IQ scores in ELBW children.
Area of Science:
- Neuroscience
- Developmental Pediatrics
- Visual Science
Background:
- Extremely low birthweight (ELBW) children are at risk for neurodevelopmental challenges.
- Periventricular brain injury (PVBI) in ELBW infants is associated with poorer academic outcomes.
- The magnocellular theory of dyslexia suggests visual pathway dysfunction may contribute to learning difficulties.
Purpose of the Study:
- To investigate visual motion processing in ELBW children.
- To determine if visual pathway dysfunction underlies academic deficits in ELBW children.
- To explore the relationship between visual processing, brain injury, and cognitive performance in ELBW children.
Main Methods:
- Compared motion processing in ELBW children (with and without PVBI) and full-term controls using a motion-defined form recognition task.
- Assessed PVBI using neonatal cranial ultrasound.
- Administered the Wechsler Intelligence Scale for Children-Third Edition (WISC-III).
Main Results:
- ELBW children exhibited significant impairments in motion processing compared to controls (71% >3 SD below mean).
- Motion processing deficits were not directly linked to PVBI or reading/spelling abilities.
- Difficulties in motion processing correlated with lower Performance IQ subtest scores in ELBW children.
Conclusions:
- ELBW children demonstrate substantial visual motion processing impairments.
- These visual deficits appear independent of PVBI and dyslexia.
- Magnocellular pathway/dorsal stream dysfunction may contribute to visuospatial and visuomotor challenges in ELBW populations.
Abstract:
Among children born at extremely low birthweight (ELBW: < 1000 g at birth) there is an association between the presence of periventricular brain injury (PVBI) and lowered performance on tests of reading and spelling ability. The present study was designed to determine if this association might be related to underlying dysfunction in the subcortical magnocellular visual pathway or its cortical targets in the dorsal stream, a prediction motivated by the magnocellular theory of dyslexia. Thirty-five ELBW children were divided into two groups based upon the presence or absence of PVBI (no PVBI, n = 11; PVBI, n = 24). The performance of these two groups was compared to that of a group of healthy full term children (n = 12) on a motion-defined form recognition task believed to tap into the functioning of the magnocellular pathway and/or the dorsal stream. ELBW children did, in fact, show a striking impairment on this task, with 71% of the sample performing at a level more than three standard deviations below the mean of full term controls. Surprisingly, their difficulties were not found to be related to either the presence of brain injury (verified by neonatal cranial ultrasound) or to problems with reading or spelling. An association was documented, however, between difficulties with motion processing and performance on several subtests of the Performance IQ scale of the Wechsler Intelligence Scale for Children-Third Edition. This latter finding is consistent with our earlier suggestion that magnocellular pathway/dorsal stream dysfunction may underlie problems with visuospatial and visuomotor performance in this population.