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The reactivity of the electroencephalogram was studied in a group of 54 healthy adults (23 women and 31 men, aged 23-80 years). The amplitude ratio between the situation with eyes closed and that with eyes open (EC/EO ratio) was calculated from quantitative parameters for each subject. The whole group was further divided into two subgroups according to age (younger than 60 and older than 60 years). In the temporo-occipital bipolar derivations (T6-O2, T5-O1), a negative correlation was found between alpha amplitude ratio and age in the whole group and especially in the subjects older than 60 years.

The present study ecplored the use of redundancy analysis, a multivariate technique for assessment of interset association, to examine facial muscle contamination of EEG recordings in studies involving covert levels of emotional expression. Redundancy analyses were performed on simultaneously recorded EEG and facial EMG data obtained in an emotion induction paradigm. Redundancy indices obtained suggest that (1) the amount of variance in EEG activity that can be explained by facial muscle activity under such conditions is minimal, and (2) the EEG alpha band may be at least as or even more susceptible to muscle contamination as the beta band.

Relationships between the phase of EEG alpha waves and motor activities have been reported in the literature. In this study such a relation was investigated for electrically or mechanically evoked monosynaptic reflexes in the soleus muscle of normal humans. EEG alpha activity, derived from electrodes widespread over the ipsilateral and contralateral hemispheres, was tested but no relationships between alpha phase and reflex amplitudes were found.

The frequencies of EEG alpha rhythm and physiological finger tremor overlap at 9-10 c/sec, suggesting a functional relationship between the two mechanisms. We measured the correlation between the two rhythms when they occurred spontaneously and when rhythmical photic stimulation was applied. Rhythmical physiological finger tremor (9.7 c/sec +/- 1.06 S.D.) was accompanied by an alpha rhythm (10.3 c/sec +/- 0.51 S.D.) spontaneously, showing a one-to-one relationship at times. When photic stimulation was provided at a frequency (11 Hz) close to the subject's spontaneous alpha rhythm, a frequency-convergence occurred between finger tremor (10.3 c/sec +/- 0.68 S.D.) and the EEG (10.6 c/sec +/- 0.35 S.D.). The correlation coefficient between the two rhythms under photic stimulation was significantly higher (0.49 +/- 0.14 S.D.) than under the spontaneous condition (0.13 +/- 0.16; P less than 0.05). Consistent with this, the mean difference between finger tremor and EEG frequencies was significantly lower during photic stimulation (0.83 c/sec +/- 0.46 S.D.) than during the spontaneous condition (1.23 c/sec +/- 0.82 S.D.) (t = 2.54; P less than 0.05, t-test for correlated means). These findings indicate that the EEG and physiological finger tremor tend toward synchrony with each other in an environment of photic stimulation, supporting our hypothesis of a functional relationship between the two mechanisms.

The Taylor Manifest Anxiety Scale was used to rank 24 healthy student volunteers according to trait anxiety level. A bipolar occipital scalp electrode was used to record the resting eyes-closed EEG responses to 15 ‘neutral’ tone stimuli and response to stress inducing questions. Eighteen subjects responded to the experimental paradigm by showing phasic changes in alpha-type synchronization. In response to 15 neutral tone stimuli, 13 (73%) subjects yielded mean alpha blocking scores, while 5 subjects (28%) had mean augmentation scores. Across all 18 subjects, trait anxiety was found to be significantly correlated with alpha response tendency to tone. The high trait anxiety group, when compared to low anxiety group, showed a significantly greater tendency toward alpha augmentation both in response to sound stimuli and stress questions. No significant correlation was found between trait anxiety and the resting alpha index. Alpha response tendency to tone stimuli was significantly correlated with the resting alpha index over the entire population of 24 subjects, and for 12 subjects of the high anxiety group alone. When alpha responses were measured regardless of direction (alpha blocking or augmenting), the high anxiety group, compared to the low anxiety group, was much more homogeneous in the magnitude of responses, as shown by smaller group mean values during various phases of acute stress and significantly smaller variance of the means. When the individual mean responses during various phases of stress were measured, taking into account the direction and magnitude of responses and particularly their variance, subjects in the high anxiety group were significantly more consistent and predictable than subjects in the low anxiety group. The possible relationship between alpha enhancement, internal inhibitory processes, and behavioral rigidity was discussed. Six subjects responded to the experimental paradigm with predominance of 5–6/sec theta activity which was felt to be a genuine neocortical pattern associated with internal inhibitory processes. The results were analyzed by excluding and including the ‘theta subjects’.

Subjective reports of the spontaneous fluctuations of perception of a stabilized retinal image were recorded simultaneously with the subjects' EEG. Periods of fade-out of the image showed a high correlation with the occurrence of EEG alpha trains, whereas periods of visibility were correlated with low voltage fast activity. The consideration of motor reaction times and alpha blocking times or latencies to visual stimulation indicates that central processes control the time at which fluctuations of perception of a stabilized retinal image take place. These are not retinal events reflected in the higher levels at later times.

Correlations between resting per-cent time alpha activity and critical flicker frequency threshold (CFF) were sought in psychiatric and volunteer subjects. Test-retest correlations for each test were high, but intercorrelations were insignificant. The lack of relationship is seen as an example of the general failure to relate resting EEG variables with psychological measures; and a more fruitful area of inquiry, that of the relations of brain reactivity (change) with behavioral measures is suggested.

Seven hyperactive children underwent a reaction time (RT) test requiring prolonged (15 min) vigilance, once while receiving methylphenidate and once without medication. EEG samples taken immediately before each RT measurement were subjected to power-spectral analysis. Compared to the off-medication condition, methylphenidate reduced the RT whilst paradoxically increasing EEG alpha power relative to higher and lower frequencies in 5 out of the 7 children. On this medication, the RT increased during the course of the task, and the relative EEG alpha power increased compared to other frequencies. Off medication, RTs showed an even greater increase with prolonged vigilance, but the accompanying EEG changes were the reverse of those seen on medication. The altered EEG power spectrum on methylphenidate appears closer to that of a normal EEG, and may be related to the improvement in specific attention produced by this drug in hyperactivity.

Correlations between EP and EEG principal components are reported. The signs of the correlations appear to depend on 3 factors: frequency of the EEG, whether the EP and EEG were measured from ipsilateral or contralateral leads, and EP latency. Correlations are negative between EP amplitude (at 100-500 msec) and EEG alpha from ipsilateral leads. When the EP measurements are from leads contralateral to the eEG alpha measurements, the correlations are positive. EEG beta, however, shows the opposite pattern (ipsilateral correlations are positive, while contralateral correlations are negative). Finally, there is some indication of higher ipsilateral correlations for earlier EP components (as opposed to lower correlations for later EP components), and higher contralateral correlations for later EP components. The EPs and EEGs were taken during separate experimental conditions as part of the same experimental session. The original EP measurements were amplitudes (N100, P150, N200, and P300) to words flashed on a television screen, as S1 of a CNV paradigm. The EEGs were 4 sec epochs taken immediately upon television presentation of a word or picture problem.

Binocular pattern reversal evoked potentials (PREPs) and EEG power were recorded bilaterally from occipital scalp of 50 boys and 50 girls aged 5–14. PREP latency was unaffected by either age or gender. Amplitudes, however, were consistently larger for girls than boys, with differences diminishing by adolescence. Significant electrophysiological asymmetries were also found; larger PREP amplitudes were measured at the right occipital electrode than the left for the two waves investigated. These asymmetries were apparent in both girls and boys across all ages, although they tended to diminish with maturation. EEG alpha asymmetry did not correlate with PREP amplitude asymmetry. PREPs elicited by half-field stimulation of 8 girls aged 9–10 years determined that ‘paradoxical laterization’ of the half-field response was the same for both left and right half-fields, thus failing to account for the asymmetry of the full-field binocular response.

Evidence has been gained which suggests that the spectral properties of the excitability cycle are other than those first proposed or assumed to exist in a number of experiments and theories. Instead of appearing as a sinusoidal cycle at the alpha frequency, the excitability cycle seems to be irregular and slower on the average than the EEG alpha rhythm. The rhythm appears to be continuously operative. It is not very sensitive in its spectral composition to the conditions of illumination or the level of behavioral activity. The rhythm operates synchronously in the right and left visual cortex. Methods similar to those described here could be used to map the extent to which synchrony is maintained in structures throughout the brain. They also suggest new approaches for psycho-physical studies which are aimed at establishing relationships between behavioral or perceptual phenomena and measures of neural activity.

Male and female subjects performed two spatial and two verbal taskswhile EEG was recorded from right and left temporal and parietal sites. Measures of alpha band power asymmetry, coherence and phase angle were derived. Spatial tasks produced increased coherence within the right hemisphere. Interhemispheric coherence was higher for females, and at parietal than at temporal sites. Power asymmetry effects confirmed previous findings, reflected upon sex differences in cerebral lateralisation and upon strategies associated with functional cerebral organisation for task performance. The relation to performance studied and the value of the method in investigating dynamic functional organisation are discussed.

Three matched groups, each of seven 11-year-old children with good, average and poor ability to concentrate were selected. Evoked potentials and EEG alpha amplitude changes after visual imperative stimuli were studied in warned reaction time experiments. The children with poor ability to concentrate (compared with the other groups) showed longer latencies of the P 2 component and reduced amplitudes of the P 2 -N 2 deflection at the vertex. Similar, although attenuated, effects were found in the F z derivation. No group effects could be established for O z . These findings are discussed in relation to group differences in pre-stimulus negativity and alpha attenuation, as reported in a previous paper (Grunewald-Zuberbier et al. 1978).