Abstract:
Premature birth is associated with a range of risk factors for abnormal neurodevelopment. The aim of this study was to assess the relationships among gestational age at birth, cortical thickness, global motion perception and functional activation of dorsal extrastriate visual area MT (hMT+) in a group of 7 year old children who were born preterm. Clinical measures of visual function were also obtained. The hypothesis was that gestational age would influence each of the measures of neurodevelopment. Measures of brain structure and function were made using functional and structural MRI and global motion perception was assessed using psychophysical measurements of motion coherence thresholds. The psychophysical stimulus was also used to activate MT during fMRI. The results demonstrated that MRI measures are possible in 7-year old children at risk of abnormal neurodevelopment. Measures of cortical thickness were obtained from 29/33 children and MT activity was seen in 9 of the 24 children for whom fMRI data was successfully collected. Cortical thickness, the functional response of MT, global motion perception, visual acuity and stereopsis were not influenced by gestational age at birth. fMRI measurements revealed a greater BOLD response in MT for coherent relative to incoherent global motion and the magnitude of the BOLD response was significantly positively correlated with psychophysical measurements of motion coherence thresholds (p = 0.007). This result links motion coherence thresholds to MT function in children for the first time. BOLD activity in MT also correlated positively with the cortical thickness of the occipital lobe (p=0.036) (as well as to that of the whole brain (p=0.034). These results indicate that the severity of prematurity does not necessarily determine long-term neurodevelopment and that behavioural measures of global motion perception relate to functional activation of MT in children.
