Magnetoencephalography reveals slowing of resting peak oscillatory frequency in children born very preterm

Abstract

Resting cortical activity is characterized by a distinct spectral peak in the alpha frequency range. Slowing of this oscillatory peak toward the upper theta-band has been associated with a variety of neurological and neuropsychiatric conditions and has been attributed to altered thalamocortical dynamics. Children born very preterm exhibit altered development of thalamocortical systems. To test the hypothesis that peak oscillatory frequency is slowed in children born very preterm, we recorded resting magnetoencephalography (MEG) from school age children born very preterm (≤ 32 wk gestation) without major intellectual or neurological impairment and age-matched full-term controls. Very preterm children exhibit a slowing of peak frequency toward the theta-band over bilateral frontal cortex, together with reduced alpha-band power over bilateral frontal and temporal cortex, suggesting that mildly dysrhythmic thalamocortical interactions may contribute to altered spontaneous cortical activity in children born very preterm.

Figure 1

The sensor montage and regional groupings. Gray circles represent sensors used in the analysis of resting MEG by cortical sector, black circles denote midline sensors excluded from regional analyses, and black lines denote the boundaries of cortical regions in the sensor level analysis. Letters indicate cortical regions: L = left, R = right, F = frontal, C = central, T = temporal, P = parietal, O = occipital.

Figure 2

Global power spectrum of spontaneous MEG activity for very preterm children and full-term controls averaged over all 151 sensors. The blue line represents the global power spectrum for the full-term controls, the red line represents that of the very preterm children.

Figure 3

A) Shift of peak oscillatory frequency in very preterm children, relative to full-term controls, in each cortical region. The magnitude of frequency shifts are denoted by colour (red -1 to -2 Hz; orange -0.5 to -1 Hz; yellow 0 to -0.5 Hz; green 0 to +0.5 Hz) and statistically significant group differences are labled (* p < 0.05; ** p < 0.005). B) Reduction of alpha (8 – 14 Hz) power in children born very preterm, relative to full-term controls, in each cortical region. Colours represent the magnitude of group differences (red -50 to -75 femptotesla (fT); orange -25 to -50 fT; yellow 0 to -25 fT) and statistically significant differences are indicated (* p < 0.05; ** p < 0.02; ¶ p < 0.003).