Dorsal and ventral cortical stream function in normal development and in at-risk infants born prematurely
Lead Research Organisation:
University College London
Department Name: Psychology
Abstract
Brain networks to interpret information from the eyes are among the earliest to develop, and so we can use measures of vision to tell us whether an infant?s brain is developing normally. Within the brain there are two major visual networks, the ?ventral stream? for identifying patterns, objects and faces, and the ?dorsal? stream which registers the movements and positions of objects to control actions such as reaching. We have found that the ?dorsal stream? is particularly vulnerable in children with certain genetic developmental disorders e.g. Williams Syndrome, autism, and in children who have suffered brain damage, often due to periods of oxygen lack around birth.
We will devise new ?brain wave? measures for infants and children alongside child-friendly computer tests to measure the normal course of relative development in dorsal and ventral streams. We will use different types of motion (dorsal) e.g. the outward movement that occurs when we move forwards, and the relative movement by which we see an object move against its background. We will compare these to children?s ability to see similar but static versions of these patterns, which are processed in the ventral stream.
We will apply these tests to study development in infants born very prematurely, who are at risk of lifelong problems, ranging from attention deficits (ADHD) to severe cerebral palsy. As clinical trials of therapies in the newborn periodwith special intervention therapies are introduced, a major difficulty is the long delay between intervention around birth, and much later ages at which these children?s abilities can be measured. We will bridge this gap by designing safe, effective tests for babies in the first months of life, to measure visual processing in the dorsal and ventral streams. We will compare our test results with MRI brain imaging analyses carried out at birth) and with development up to 18 months, to identify which brain systems are most vulnerable to damage, which can recover or be substituted, and which infant tests are the best predictors of later abilities.
Our longer term goal is to design and use these sensitive tests for specific aspects of vision to evaluate the effectiveness of early treatment in children at high risk of later problems, whether they arise from genetic disorders or early brain damage, so that effective therapies can be introduced as early as possible to reduce lifelong mental health problems and reduce healthcare and educational costs.
We will devise new ?brain wave? measures for infants and children alongside child-friendly computer tests to measure the normal course of relative development in dorsal and ventral streams. We will use different types of motion (dorsal) e.g. the outward movement that occurs when we move forwards, and the relative movement by which we see an object move against its background. We will compare these to children?s ability to see similar but static versions of these patterns, which are processed in the ventral stream.
We will apply these tests to study development in infants born very prematurely, who are at risk of lifelong problems, ranging from attention deficits (ADHD) to severe cerebral palsy. As clinical trials of therapies in the newborn periodwith special intervention therapies are introduced, a major difficulty is the long delay between intervention around birth, and much later ages at which these children?s abilities can be measured. We will bridge this gap by designing safe, effective tests for babies in the first months of life, to measure visual processing in the dorsal and ventral streams. We will compare our test results with MRI brain imaging analyses carried out at birth) and with development up to 18 months, to identify which brain systems are most vulnerable to damage, which can recover or be substituted, and which infant tests are the best predictors of later abilities.
Our longer term goal is to design and use these sensitive tests for specific aspects of vision to evaluate the effectiveness of early treatment in children at high risk of later problems, whether they arise from genetic disorders or early brain damage, so that effective therapies can be introduced as early as possible to reduce lifelong mental health problems and reduce healthcare and educational costs.
Technical Summary
This proposal combines basic research on the development of global visual processing in infancy and childhood, with clinical application using these methods for assessment of at-risk, very premature infants.
Global visual processing occurs beyond primary visual cortex in two cortical streams, the ?ventral? underpinning recognition of patterns, objects and faces, and the ?dorsal? stream for spatial and motion processing and visual control of actions. We have shown differential human development of these two streams in infancy and childhood, using form and motion coherence sensitivity as markers of ventral and dorsal global processing. We have identified ?dorsal stream vulnerability?, a relative deficit or delay in global motion compared to global form sensitivity in a range of neurodevelopmental disorders including Williams Syndrome, and hemiplegia. Our methods have been followed by others, extending dorsal vulnerability to autism, Fragile X and congenital cataract.
Basic research: to understand differential development and vulnerability, we will devise new behavioural and electrophysiological measures to analyse specific sub-systems within these two streams beyond primary visual cortex. We will develop and use high density VERP recording methods with a geodesic array, to distinguish the spatio-temporal signatures of specific global processes for motion and form, e.g. coherence detection, segmentation, localization of optic flow. We will investigate the functional onset of these processes in normally developing infants under 6 months of age. With psychophysical methods specially adapted for normally developing 4-12 year olds, we will track their developmental trajectory, at a time when vulnerability in developmental disorders is apparent. We will relate individual variations to other measures of visuocognitive and visuomotor performance.
Proof of concept clinical study: we will apply these new VERP measures to infants born very prematurely (under 32 weeks gestation). This will extend our previous work on premature infants using tests of primary cortical function, to test higher level visual processing in dorsal and ventral streams. Results will be compared with measures of brain structure from neonatal MRI, and neurological/behavioural development up to 18 mo. The longer term goal is to use these visual brain processing measures to assess brain plasticity and development, and so meet the need for reliable early surrogate outcome measures in the first months of life. These would predict outcome in a number of high-risk groups, including children with specific genetic developmental disorders, and so gauge the effectiveness of early intervention in improving cognitive status in later childhood.
Global visual processing occurs beyond primary visual cortex in two cortical streams, the ?ventral? underpinning recognition of patterns, objects and faces, and the ?dorsal? stream for spatial and motion processing and visual control of actions. We have shown differential human development of these two streams in infancy and childhood, using form and motion coherence sensitivity as markers of ventral and dorsal global processing. We have identified ?dorsal stream vulnerability?, a relative deficit or delay in global motion compared to global form sensitivity in a range of neurodevelopmental disorders including Williams Syndrome, and hemiplegia. Our methods have been followed by others, extending dorsal vulnerability to autism, Fragile X and congenital cataract.
Basic research: to understand differential development and vulnerability, we will devise new behavioural and electrophysiological measures to analyse specific sub-systems within these two streams beyond primary visual cortex. We will develop and use high density VERP recording methods with a geodesic array, to distinguish the spatio-temporal signatures of specific global processes for motion and form, e.g. coherence detection, segmentation, localization of optic flow. We will investigate the functional onset of these processes in normally developing infants under 6 months of age. With psychophysical methods specially adapted for normally developing 4-12 year olds, we will track their developmental trajectory, at a time when vulnerability in developmental disorders is apparent. We will relate individual variations to other measures of visuocognitive and visuomotor performance.
Proof of concept clinical study: we will apply these new VERP measures to infants born very prematurely (under 32 weeks gestation). This will extend our previous work on premature infants using tests of primary cortical function, to test higher level visual processing in dorsal and ventral streams. Results will be compared with measures of brain structure from neonatal MRI, and neurological/behavioural development up to 18 mo. The longer term goal is to use these visual brain processing measures to assess brain plasticity and development, and so meet the need for reliable early surrogate outcome measures in the first months of life. These would predict outcome in a number of high-risk groups, including children with specific genetic developmental disorders, and so gauge the effectiveness of early intervention in improving cognitive status in later childhood.