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Biomedical subjects

G Grünewald

Publications and source records attributed to G Grünewald.

7 recordsLinked to original sources
PubMed1979

Cerebral potentials during smooth goal-directed hand movements in right-handed and left-handed subjects.

During smooth goal-directed hand movements a negative potential shift can be recorded from the human scalp. This goal-directed movement potential (GDMP) is preponderant over central areas with a maximum at the vertex and, over the motor cortex, contralaterally larger than ipsilaterally to the moving hand. In 11 right-handed and 6 left-handed subjects, the morphology and distribution of these potential shifts were studied in relation to task differences, moving hand and handedness. The results show a functional differentiation of two components of the GDMP: (1), a lateralized, slow negative wave, restricted to the precentral area and selectively varying with the hand used, and (2), a widespread, bilateral symmetrical component, selectively influenced by task-specific and individual factors. Two effects reflect an influence of the subject's handedness on the GDMP: (A) averaged for both hand conditions, there are larger amplitudes over the hemisphere contralateral to the dominant hand, and (b), averaged for both hemispheres, larger amplitudes result from using the non-dominant hand.

Adolescent↗
PubMed1979

Relationships between the late component of the contingent negative variation and the bereitschaftspotential.

The purpose of this study was to determine whether the late component of the contingent negative variation (CNV) in a S1-S2-respond paradigm shares critical features with the Bereitschaftspotential (BP) prior to self-paced voluntary movements. In a group of 8 subjects, the late CNV and the BP exhibited: (a) similar effects of response speed variation, (b) corresponding influences of subjective factors, and (c) a similar scalp distribution with the exception that the BP was much more lateralized. In contrast, no such relationships were found between early CNV and BP.

Brain↗
PubMed1978

Contingent negative variation and alpha attenuation responses in children with different abilities to concentrate.

In three paralleled groups, each of seven children (age, 11 years) with reliable high, average and low ability to concentrate, measured by psychological tests, the contingent negative variation (CNV) and the concomitant alpha attenuation responses were studied in warned reaction time experiments. Stimuli were tone (S1) and patterned light (S2). In half of the trials, S2 was a square, in the other half a triagle, stimuli being projected in random order onto the fixation point. In two experiments the children had to react (a) to each type of S2, and (b) selectively to one type of S2. Significant group differences were found. In comparison to the children with low ability to concentrate, the children with average and especially those with high ability to concentrate showed: (1) stronger central occipital alpha attenuation responses to the warning stimulus, but no differences in the early CNVs; (2) more occipital alpha reduction and enhanced development of central negativity before the imperative stimulus; (3) task-specific modulation of these responses, i.e. larger pre-S2 rise in negativity in the simple reaction task, and stronger pre-S2 reduction of alpha amplitudes in the discriminative reaction task.

Alpha Rhythm↗
PubMed1978

Late components of average evoked potentials in children with different abilities to concentrate.

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 P2 component and reduced amplitudes of the P2-N2 deflection at the vertex. Similar, although attenuated, effects were found in the Fz derivation. No group effects could be established for Oz. These findings are discussed in relation to group differences in pre-stimulus negativity and alpha attenuation, as reported in a previous paper.

Attention↗
PubMed1975

Hyperactive behavior and EEG arousal reactions in children.

EEG arousal reactions and parameters of spontaneous EEG activity were studied in two extreme groups of behavior problem children (11 hyperactives and 11 non-hyperactives), selected on the basis of a rating of motor restlessness the core symptom of the "hyperactivity syndrome". The EEG was recorded in three reaction time experiments: a tone light conditioning paradigm and two series with random stimulation. An automatic analysis of EEG parameters was employed to describe the time functions of alpha amplitudes in the single trial. The main findings are: 1. In periods free from stimulation, hyperactive children have higher alpha and beta amplitudes, more alpha waves and a smaller amount of beta waves. This indicates a lower state of EEG arousal in the hyperactives. 2. The amplitude reduction to tone (in the single trial) develops more slowly in the hyperactive group. This group difference increases over the experimental situations. 3. The arousal responses to tone, in terms of the level of maximum amplitude reduction, become comparably weaker in the hyperactives across the experiments. 4. Under all experimental conditions the hyperactives exhibit shorter arousal responses to the light stimulus than the non-hyperactive children. 5. Reaction time performance of the groups is clearly different, hyperactives showing the longer latencies. 6. Although conditional changes in the arousal reactions to both stimuli are reliably demonstrable in all children, the groups show no difference in the corresponding measures. These findings are discussed under the aspects of activation and of attention behavior of the subjects.

Acoustic Stimulation↗