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Biomedical subjects

G Zeller

Publications and source records attributed to G Zeller.

27 records · Page 2Linked to original sources
PubMed1983

[Laterality of hospitalized endogenous-depression patients].

Compared to normals, groups of inpatients with unipolar and involutional depression show a higher proportion of consistent right-handers, whereas bipolar patients do not differ from normals. All patient-groups show a clearly higher proportion of persons with a "dominance" of the right thumb when habitually clasping the hands or fingers. The variables "eyedness" and "familial sinistrality" do not show significant differences between groups. When drawing geometric figures in a bimanual-coordinated fashion, all patient groups demonstrate a prevalence of simultaneous counter-clockwise drawing with both hands, whereas normals overwhelmingly prefer a discordant mode of drawing, the left hand acting counter-clockwise and the right hand clockwise. We interpret this behavior in depressives to be an expression of an interhemispheric functional relationship in which the left hemisphere is subordinated to the right hemisphere.

Adult↗
PubMed1983

[Changes in the electric organization of the brain in visual search and discrimination processes of different degrees of difficulty].

EEG activity during visual search processes with different degrees of discrimination difficulty was investigated in 13 male subjects. In accordance with the paradigm used by Neisser, 17 corresponding lists of rounded or angular letters were displayed. The task was to select the target letter Z from each list. The discrimination of the letter Z out of the lists of angular letters is the more difficult task. Spectral analysis shows a significant change in alpha-frequency structure during the more difficult search process. There is a shift of the dominant alpha-frequency from 11.5 to 10 Hz with a significant increase and concentration of power in the dominant frequency. This concentration of alpha-power around 10 Hz is more pronounced in the right occipital region than in the left. Concomitantly, there is a significant increase of power in subharmonic theta-frequencies. By consecutive principal analysis of spectral data these results were further differentiated and confirmed. The changes in the alpha- and theta-band during the more difficult search process are the expression of a complex transformation of EEG-frequency structure and patterning which cannot be interpreted by the usual concepts based on the theory of activation. Moreover, they seem to be the neurophysiological correlate of the accommodation (Piaget) of the neurodynamic processes to the altered perceptual conditions and to their effects on the internal matching process.

Adult↗
PubMed1976

[Psychophysiological studies of EEG, operational performance and the dynamics of vigilance regulation. I. The EEG during performance of Brickenkamp's attention-concentration test (test d 2) (author's transl)].

During the performance of the d 2 test developed by Brickenkamp (standardized test of attention and concentration), occipital EEG activity was registered telemetrically in 10 male students aged 25 to 32 years. Simultaneously, the pencil markings performed by the subjects, indicating the time course of their pattern recognition and discrimination, were recorded by means of a piezo-electrical transducer. The EEG behavior during test performance was evaluated by serial spectral analysis. The analysis of the EEG parameters derived from it (total power, absolute and relative alpha-power) showed that there is a relationship between these EEG measures reflecting the regulation of cortical vigilance and the error rate in the concentration test. While subjects with low error rate present a heightening of cortical arousal focused in the right occipital area, subjects with higher error rate tend to have a higher degree of general cortical activation.

Adult↗