Neuronal maturation and N-acetyl-L-aspartic acid development in human fetal and child brains.

The developmental changes in N-acetyl-L-aspartic acid (NAA) were assessed in human fetal and child brains by means of high resolution proton magnetic resonance spectroscopy (MRS). NAA was detected in the cerebral cortex and white matter of fetuses of 16 weeks' gestation. NAA increased gradually from 24 weeks' gestation and remarkably from 40 weeks' gestation to 1 year of age. The developmental changes in tissue NAA in postnatal brains were found to be similar to those of NAA/Cr on clinical proton MRS. As the neuronal cell density in the cerebral cortex decreases with dendritic maturation, an increase in NAA with age may reflect the normal and abnormal development of axons, dendrites and synapses as well as neuronal soma.