Development of sleep spindles in young children and adolescents.

The development of sleep spindles was studied quantitatively in 32 healthy subjects between the ages of 4 and 24 years. The peak frequency distribution of the spindles showed a bimodal pattern with 11.0 to 12.75 Hz in the frontal area and 12.5 to 14.5 Hz in the centroparietal area. The two types of spindle activity showed different courses of maturation. The peak frequency of the centroparietal spindles gradually increased linearly with age, whereas the frontal spindles abruptly increased in frequency during early adolescence. Regarding the power spectra, while centroparietal spindles showed little change in power from 4 to 24 years of age, frontal spindles decreased remarkably in power and became stable at about 13 years of age. The two types of spindles and the difference in their development may suggest the existence of different generators or a topographical difference during maturation in the thalamocortical network. The frontal spindle activity could be a good indicator to evaluate CNS maturation in young children and adolescents.