ABSTRACT
Topographic aspects of EEG development of normal children and adolescents from 6 to 17 years are investigated with respect to various spectral parameters. The topographic distribution of spectral band power does not change between hemispheres across age. Changes take place, however, in the antero-posterior dimension. For the bands theta, alpha 1 and alpha 2 (and less so for delta) maturation starts at posterior derivations and ends at anterior derivations. For the band beta 2 (and to some extent also for beta 1), development progresses from Cz to Pz and further to occipital, lateral, central and frontal derivations. Principal component analysis (PCA) leads to a more parsimonious and better interpretable description of broad-band power and of its topographic distribution. Broad-band coherences increase with age, though to a modest degree. The different magnitudes of coherence between different regions can be largely accounted for by the interelectrode distances. Coherences, too, can be described in a more parsimonious and better interpretable way via PCA. The 3 components extracted reflect firstly the overall level of coherence, secondly the coherences of the occipital regions with all other regions and thirdly antero-posterior versus left-right coherences.
Subject(s)
Aging/physiology , Brain Mapping , Electroencephalography , Adolescent , Brain/physiology , Child , HumansABSTRACT
Development in quantitative EEG parameters is studied for a sample of 158 normal children and adolescents aged 6-17 years. This is of interest both for increasing basic knowledge of human neurophysiology and for obtaining age standardized norms, useful in clinical research and applications. After selecting an appropriate epoch and correcting for EOG artifacts, the EEG at 8 derivations was submitted to spectral analysis in order to extract broad-band parameters in absolute and relative power. Change in EEG band power across age was quantified by polynomial regression analysis. This opened automatically the possibility to obtain age-standardized EEG norms. Development was for most EEG parameters non-linear, with more pronounced changes for absolute than for relative power. No sex differences and no pubertal spurt could be identified in contrast to most somatic quantities. A detailed statistical analysis revealed, however, that this might be due to using cross-sectional data. All bands except for alpha 2 decreased in absolute power, whereas the fast bands increased and the slow bands decreased in relative power. Strong evidence was found for a substituting process between theta activity and fast alpha activity.
Subject(s)
Aging/physiology , Brain/physiology , Electroencephalography , Adolescent , Child , Female , Humans , Male , Reference ValuesSubject(s)
Blinking , Electroencephalography , Eye Movements , Statistics as Topic , Child , Electrooculography , HumansABSTRACT
The transfer of EOG activity into the EEG is investigated for eyes open (EO) eyes closed (EC), relying on spontaneously produced EOG activity. Blinks were prominent with EO and eye movements with EC. A frequency domain approach is more appropriate compared to treating the EOG influence as constant over frequency (i.e., assuming that a fraction of the EOG amplitude is present at EEG derivations). A major problem is to take into account the coherent EEG activity present at the EOG derivations, and this holds true in particular for the higher frequency bands were EOG power is relatively low. Blinks and eye movements have different spectral patterns and are also transferred differently to the locations on the skull. Eye movements are transferred best at low frequencies. The gains of blinks peak in the theta band. Due to high random variability in the individual gain functions, sample average gain functions ('grand means') rather than individual ones were studied.
