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D N Donker

Publications and source records attributed to D N Donker.

5 recordsLinked to original sources
PubMed1979

Computer analysis of the EEG as an aid in the evaluation of dietetic treatment in phenylketonuria.

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.

Adolescent↗
PubMed1978

Interhemispheric relationships of reponses to sine wave modulated light in normal subjects and patients.

(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-).

Attention↗
PubMed1975

Harmonic composition and topographic distribution of responses to sine wave modulated light (SML), their reproducibility and their interhemispheric relationship.

1. Responses to sine wave modulated light (SML) were recorded bipolarly from the occipital, parietal and temporal scalp areas on the right and the left sides of 9 normal individuals. Their harmonic composition was determined by means of Fourier analysis. 2. The wave form of the responses was rather complex in relation to the stimulus and differed according to stimulation frequency and localization. 3. The components of the responses were principally the 1st and 2nd harmonics. 4. The amplitudes of the harmonics were usually largest over the occipital and smallest over the parietal scalp areas. 5. Considerable intra-individual amplitude variabilities of both harmonic component amplitudes existed in all areas of all individuals. 6. The interhemispheric amplitude correlations of 1st and 2nd harmonic components, simultaneously recorded in homologous occipital, parietal and temporal areas, were measured by means of Kendall's rank correlation test. 7. The interhemispheric synchrony of the harmonic components was measured by determining the phase differences between each of the response components in homologous right and left scalp areas. 2. In subjects with a high amplitude correlation a strong synchrony existed and vice versa. 9. It is suggested that the interhemispheric relationships between harmonic components of the responses to SML might be of importance for clinical application. This opinion is supported by the fact that through SML evoked responses a considerable data reduction is obtained in comparison with the responses to light flashes.

Adolescent↗
PubMedDate not supplied

[Computer analysis of the EEG as an aid in terminating diet therapy in phenylketonuria].

In 6 patients with PKU, being on a low phenylalanine diet, the effect of reintroduction of phenylalanine on the E.E.G. was studied. The children, therefore, received daily loads of 100 or 150 mg phenylalanine/Kg bodyweight, equally divided over the meals. Computerized spectral analysis of the E.E.G's was performed during and after the loading tests. This made quantification possible of the following E.E.G. changes: 1) the increase of activities in the theta frequency band (4-8 Hz); 2) the frequency change of the alpha rhythm; 3) the change of the degree of synchrony between identical frequencies occurring in different derivations. A linear relation was found between these quantified E.E.G. parameters and the phenylalanine blood-level. After stopping the loading test E.E.G. abnormalities reversed suggesting that they could be considered as a measure for the degree of intoxication caused by the phenylalanine and/or its metabolites. It is suggested that the E.E.G. data may be useful parameters for alleviation or termination of the diet.

Alpha Rhythm↗