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We have recorded control subjects, neurological and psychiatric patients (n = 217 sequences recorded over both hemispheres). Minicomputers (HP Fourier analyzer, HP 1000) for spectral analysis provided 10 spectral parameters over 5 spectral frequency bands (delta, theta, alpha, beta 1, beta 2, raw EEG). For each recorded sequence, 90 EEG maps could be computed over both hemispheres. Topo-EEGs were stored in an EEG image data bank. An EEG mapping microcomputer system linked with a digital polygraph (Alvar Electronic, REEGA 2000) has been used simultaneously. White noises have been fed into both computers for testing spatial resolution. Ten topo-EEGs have been recorded in control subjects and patients. The microcomputer system has provided very reliable topographical results when compared to similar maps generated by the minicomputer. A common average reference has been used. First clinical applications have been studied (brain strokes, brain tumors). The method appears very reliable in comparison with CT scans.

This article presents the characteristics of ECoGs of arousal, slow wave sleep and paradoxical sleep in the rat, in terms of analysis of data. In a first part, we have applied four different methods of analysis to the three tracings: the instantaneous amplitude histograms computation, the integrative method of Drohocki, the spectral analysis and the normalized slope descriptor method of Hjorth. Each method provides, after data reduction, characteristic parameters of the tracings. A graph which displays peak spectral frequency versus mean integrated value is enough to discriminate between the 3 quantified tracings. Multivariate discriminant analysis reveals that 3 coefficients altogether allow a good discrimination. In the second part we ask the question: which kind of signal is the paradoxical sleep tracing? After the impossibility to choose between a narrow-band Gaussian process or a sinusoidal wave burried in noise, we propose a third kind of signal found after modulation analysis. This signal is modulated both in amplitude and frequency around a carrier frequency beeing the dominant theta rhythm.

10 male volunteers, right-handers, mean age 30.4 years, were recorded in four successive sequences: under 'eyes closed' conditions, right and then left hemisphere, followed by an 'eyes open' situation with visual attention fixed on a cartoon, right and then left hemisphere recordings. Each EEG recording was made simultaneously over 16 EEG channels for each hemisphere, according to a protocol previously described as well as Fourier analysis and EEG mapping on a minicomputer (HP 5451 C, HP 1000). Each EEG recording was stored on a cartography data base, and 90 maps could be drawn from 10 spectral parameters applied to the raw EEG and 5 frequency bands. Permutation paired Fisher tests were applied to three main EEG parameters: mean centroid frequencies, RMS amplitudes in microvolts and relative (%) amplitudes. Activation of EEG in the 'eyes open' situation during visual fixation was found compared to the 'eyes closed' situation: decreasing dominant EEG frequency and low delta and theta mean frequencies, no change in a mean alpha frequency; increasing fast mean beta frequencies, together with a major decrease in theta, alpha, beta 1 amplitudes, and a concomitant increase in raw EEG, delta and beta 2 amplitudes. Finally, the percent alpha amplitude was decreased when other percent amplitudes were increased in delta, theta, beta 1 and beta 2 frequency bands. A symmetry between hemispheres was observed in the 'eyes closed' situation. Averaged EEG maps between subjects illustrate these findings, especially relative (%) alpha amplitude maps and also maps of coefficients of resonance of the alpha rhythm.