Fig. 7.
Frontal electroencephalogram power and coherence in infants under 2 yr of age. (A) Median power spectra for two groups of subjects are shown: subjects between 4 months and 1 yr of age (n = 4; blue) and subjects between 1 and 2 yr of age (n = 3; red). The shaded bounds represent the 95% CI for these power spectra. The spectra show that slow (0.1 to 1 Hz) oscillations are consistently observed in all subjects. However, the power spectrum in subjects less than 2 yr old shows the relative absence of well-defined alpha (8 to 13 Hz) oscillations, instead showing a higher frequency broad increase in electroencephalogram power for 12 to 25 Hz oscillations. Electroencephalogram power is significantly greater in the 1- to 2-yr age group relative to the 4-month to 1-yr age group for the following frequency ranges: 0 to 15.14 Hz and 20.51 to 33.69 Hz (95% CI, bootstrap analysis). Horizontal green lines represent the frequency ranges for which there is a significant difference. (B) Median coherence in patients less than 2 yr old shows the absence of alpha (8 to 13 Hz) oscillation coherence in subjects between 4 months and 1 yr of age, with alpha oscillation coherence becoming apparent in subjects between 1 and 2 yr of age. Frontal coherence is significantly greater in the 1- to 2-yr-old age group relative to the 4-month to 1-yr-old age group for the 6.35 to 11.72 Hz frequency range (95% CI, bootstrap analysis). The horizontal green line represents the frequency ranges for which there is a significant difference.