Are there any constants in electroencephalography? Spectral peak in the range of theta band in infants

The dominant frequency band of the electroencephalogram (EEG) background in children aged 4 to 12 months is theta band. Generators of theta oscillations are poorly understood, but medial septum, hippocampus and thalamus are contributors to generating theta band activity. Given the fact that hippocampal-prefrontal pathway and thalamic-prefrontal loop are significantly interlinked, prefrontal tex can be considered as area, indirectly reflecting an activity of subcortical structures mentioned. To highlight the EEG spectral characteristics of theta activity over the prefrontal regions in infants. We examined frontal theta (4–7.9 Hz) power of high-density (128-channel HCGSN) resting EEG in normal infants with typical development at two age points: at 5 months (number: 23; mean age = 5.74 months, SD = 0.255), and at 10 months (number: 18; mean age = 10.71 months, SD = 0.58). All computations have been performed in Matlab R2016b. The channels 12,19,20,23,24,26,27,28,33,34 are selected as left channels, and symmetrically the right channels are considered as 5,4,118,3,124,2,123,117,122,116. The average power in the specified frequency range (e.i. a subband of length 0.1Hz) is determined for each left and right channel individually. Then the mean value of subband power is separately computed over the left and right channels. Finally, we compare the obtained left and right power mean values for each subband. We have revealed distinct and stable spectral peak at 4.4 Hz at both ages. Given the constancy of revealed spectral peak, we suppose that it may be supported by activity of pacemaker neurons of medial septum and/or thalamus.