H. Petsche et al., THE POSSIBLE MEANING OF THE UPPER AND LOWER ALPHA-FREQUENCY RANGES FOR COGNITIVE AND CREATIVE TASKS, International journal of psychophysiology, 26(1-3), 1997, pp. 77-97
This study is aimed at verifying the functional independence of two fr
equency bands within the alpha range. It is based on experiments that
examined the role of these two bands with regard to the amount of loca
l electrogenesis (amplitude) and the cooperation of brain areas (coher
ence) in mental tasks concerning: (1) visual perception and imagery; (
2) listening to and composing music; (3) verbal and visual creativity;
and (4) aspects of mood. In all experiments EEG were recorded for at
least 1 min during each task, separated one from another by at rest pe
riods of at least equal lengths. EEG electrodes were pasted according
to the 10/20 system (averaged ear lobes as reference). After FFT power
was calculated for all 19 electrodes, coherence was estimated for all
possible electrode pairs (i.e. 171). This was done for six frequency
ranges between 1.5 and 31.5 Hz, the alpha range having been divided in
to two (7.5-9 Hz and 9.5-12.5 Hz). The spectral parameters obtained du
ring each task were compared with those of the merged EEG at rest, sig
nificant changes (P less than or equal to 0.01-P less than or equal to
0.05) were entered into schematic maps of the brain. Generally, fewer
differences were found for amplitude than for coherence. In all four
tasks concerning visual perception the dearest differences were found
in single person studies. But also in group studies more or less disti
nct differences were found between alpha 1 and 2. Also in the series w
ith music the two alpha bands did not behave uniformly, nor were unifo
rm features found in the two series of musically trained and untrained
subjects. Distinct discrepancies were also found in a verbal and visu
al imagery task. With respect to mood, only elevated mood was correlat
ed with a decrease of coherence in alpha 2 and an increase of amplitud
e in alpha 1. This study though hinting at a different functional sign
ificance of these two alpha bands, however, does not allow to draw any
conclusions as to their distinct functional meanings. Generally, the
long-term coherence changes observed under these different mental task
s support the idea that part of information processing in the brain is
reflected by the EEG. Structural peculiarities and microelectrode rec
ordings of the cortex support this conclusion. (C) 1997 Elsevier Scien
ce B.V.