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(1) The interhemispheric amplitude correlations of the fundamental (A1) and second harmonic (A2) components of responses to sine wave modulated light were determined in the occipital, parietal and temporal scalp areas of a group of normal subjects and a group of patients with unilateral irritative EEG phenomena. The interhemispheric amplitude correlation was computed at 10- and 16-c/sec stimulation frequencies and under 3 conditions: no modulation and no attention (M-, A-), modulation 30%, and no attention (M+, A-) and modulation 30% and attention (M+, A+). The correlations wre expressed in the rank correlation coefficient of Kendall (rK). (2) Analysis of variance revealed that the interhemispheric amplitude correlation of A1 in the normal group was significantly larger than that in the patient group at a stimulation frequency of 10 c/sec and under the conditions (M-, A-) and (M+, A-). (3) Both groups presented the largest correlation coefficients in the occipital scalp area. (4) In the normal group a significant increase of rK occurred under the influence of modulation. Attention caused a decrease of the correlation coefficient of A1. In the group of patients this influence was not clear. (5) The standard deviation of the mean interhemispheric phase differences was considered as a measure of synchrony of the response components between the two hemispheres. The smallest values of standard deviation were found in the occipital scalp area of the normal group at 10 c/sec stimulation frequency. Considerable variations between individuals were observed in both groups. (6) The correlation between the interhemispheric amplitude correlation (rK) and the interhemispheric synchrony was influenced by changing modulation depth from 0 to 30% and by introduction of attention, mostly in the group of normal subjects. This phenomenon was considered to support the theory that in patients with unilateral EEG disturbances the interhemispheric relations are different from those in normal subjects. (7) The findings as to amplitude correlation (rK) were the same under the condition (M-, A-) as under the condition (M+, A-).

The effect on the EEG of the reintroduction of phenylalanine in the diet of 6 patients with PKU on treatment was studied. Patients received daily loads of 100 or 150 mg L-phenylalanine/kg, equally divided over the meals, and computerized spectral EEG analysis was performed. The following EEG changes were seen: (1) occurrence of activity in the low frequency band (2--5 c/sec), (2) change of frequency of dominant rhythms; (3) change in the degree of synchrony between identical frequencies, occurring in different derivations. EEG changes increased quantitatively parallel to increasing blood phenylalanine and reversed after stopping the phenylalanine administration, suggesting that the EEG abnormalities are a measure for the degree of intoxication caused by phenylalanine or its metabolites. It is suggested that the EEG data may be useful deciding to terminate the diet in PKU.

An investigation has been carried out in 25 normal subjects on quantitative differences of mu rhythm and alpha rhythm parameters. The parameters were frequency, average power over 102 sec and bilateral coherence. It was found that: (1) in the majority of cases the frequencies of the mu rhythms were higher than those of the alpha rhythms; (2) in the majority of subjects the average power was smaller for the mu rhythms for the alpha rhythms; (3) in none of the subjects was bilateral coherence of mu rhythms observed while in the majority the alpha rhythms were obviously bilaterally coherent. It is proposed that the latter difference represents a fundamental difference in the origin of alpha and mu rhythms.

An investigation has been carried out in a group of 84 (+2) patients suffering from myotonic dystrophia (Curschmann-Steinert). Manual measurements show that in these patients: (1) the alpha rhythms have low frequencies, related to the age of the patient and to the duration and severity of the disease; (2) the alpha rhythms are regular, monotonous; (3) the alpha rhythms have small amplitudes; there appears to be no relation between alpha frequency and amplitude; (4) the alpha indices are high during eyes closed as well as during eyes open. The computer measurements generally appear to concur with the above and in addition show that the bilateral and longitudinal coherences are high, indicating considerable synchrony of the alpha rhythm over large areas on both sides of the head. The possible significance of these observations is discussed.