Functional brain imaging using fMRI and optical topography in infancy

We performed functional magnetic resonance imaging and optical topography over the visual cortex of subjects during sedation with pentobarbital, and 8-Hz flickering light was intermittently projected onto their eyelids. Two age groups were analyzed: infants <60 days old and those >60 days old (corrected for gestational age at birth). The stimulus-related signal change was positive in the lateral geniculate nucleus regardless of the infant's age, but it reversed in the primary visual cortex from positive in the infants less than 60 days old to negative in the infants more than 60 days old (Experiment 1). We also investigated spontaneous changes in the cerebral oxygenation state of neonates and infants aged 1 month during quiet sleeping by using a form of multi-channel near-infrared spectroscopy: non-invasive optical topography. Spatially synchronized oscillations of changes in the concentration of oxy-hemoglobin (oxy-Hb) and deoxy-Hb were observed throughout the occipital cortex in neonates but not in the infants aged 1 month. Time series analysis based on the theory of non-linear oscillations showed that the mean periods of the oscillation for each infant ranged from 11 to 18 s. The phase lag of oxy-Hb relative to deoxy-Hb was stable at about 3 pi/4 in neonates but in the infant aged 1 month, time lag was unstable. These findings may be due to rapid synaptogenesis in early life. (C) 2002 Elsevier Science B.V. All rights reserved.