[Developmental characteristics of frontal spindle and centro-parietal spindle]

The frequency and power of EEG sleep spindles during sleep stage 2 were analysed in 56 subjects between the age of 3 to 25 years in order to define the maturational pattern of two types of spindles. Although 24 of the 56 subjects were medicated with a single anticonvulsant, there was no remarkable difference in spindle maturation patterns between the subjects who received monotherapy and unmedicated subjects. The frontal spindles matured differently than centro-parietal spindles. The frequency of centro-parietal spindles developed gradually with age, whereas frontal spindles matured with a rather sudden increase of frequency during puberty. Although the power of centro-parietal spindles showed little changes with age, the power of frontal spindles declined remarkably during the first decade and settled down to a constant level after puberty. The developmental characteristics of these two kinds of spindles may reflect a difference in synchronicity of the thalamo-cortical pathway maturation including the inhibitory system. Both centro-parietal spindles and frontal spindles tended to develop slightly earlier in females than in males. The lag of spindle maturation in males might implicate developmental procedures in females. Separate observation of these two types of spindles is necessary for better understanding of sleep spindles as an indicator of central nervous system development.