Hemisphere asymmetry in sympathetic control of the human myocardium.

Hemisphere asymmetry in sympathetic control of myocardial performance was studied in healthy human subjects using lateralized film presentation for selective sensory stimulation of the hemispheres and impedance cardiography for the evaluation of cardiac output, systolic time intervals and myocardial contractility. Results revealed a clear and consistent right hemisphere predominance in sympathetically mediated control of various components of myocardial performance. There is reason to assume that the obtained hemisphere differences in autonomic control of the heart are self-reliant processes not depending on emotion-related hemisphere asymmetry. As far as we know, this is the first study examining the distinct roles of the cerebral hemispheres in neural control of ventricular myocardial functions.

Hemisphere asymmetry in parasympathetic control of the heart.

Hemisphere asymmetry in the control of parasympathetic outflow to the sino-atrial node of the heart was studied in healthy human subjects using lateralized film presentation for selective sensory stimulation of the hemispheres and power spectral analysis of heart rate variability as a measure of vagal tone. There was a clear and consistent left hemisphere predominance in the control of parasympathetic modulation of cardiac activity which cannot be attributed to differences in emotional processing. Supplementing previous findings of our research group, the present study indicates that control of autonomic cardiac activity at the level of the cerebral cortex seems to be characterized by a division of responsibility between both hemispheres, sympathetic activity being mainly controlled by the right hemisphere and parasympathetic activity being under the left hemisphere's main control.

The right hemisphere and the human stress response.

Evidence is presented that most components of the human stress response are influenced asymmetrically by the cerebral hemispheres. The right hemisphere is endowed with a unique response system preparing the organism to deal efficiently with external challenges. Therefore, both the hypothalamic-pituitary-adrenocortical (HPA) axis and the sympathetic-adrenomedullary (SA) axis seem to be under the main control of the right hemisphere.

Emotion-related hemisphere asymmetry: subjective emotional responses to laterally presented films.

To investigate whether the cerebral hemispheres differ in their subjective emotional responses 54 adult subjects were presented two films of different emotion-related qualities (positive and negative film) either to their left or right hemisphere. The films were exposed by means of a technique for the lateralization of visual input that allows prolonged viewing while permitting free ocular scanning. Subjective emotional responses were assessed by means of a continuous rating of emotional arousal experienced during the movie as well as by retrospective ratings of ten different emotional qualities. Presenting both films to the right hemisphere resulted in stronger subjective responses in the continuous emotion rating as well as in some retrospectively assessed ratings compared to left-hemispheric presentation. The effects were more pronounced for the negative film. Taken together, the findings suggest a higher responsiveness of the right hemisphere in subjective emotional experience.

Neuroendocrine brain asymmetry and physical complaints.

It was examined whether there is an association between physical health and alterations of normal brain asymmetry in cerebral control of neuroendocrine activity. In particular, it was studied whether right-handed subjects showing a high amount of physical complaints and recurrent diseases differ in direction and degree of brain asymmetry in cerebral control of cortisol secretion from subjects with only few physical complaints. Lateralized brain activation was achieved by presenting an emotionally aversive film to the subjects' left or right visual hemifield, using a technique for lateralizing visual input that allows prolonged viewing while permitting free ocular scanning. Results revealed a clear association between a high degree of physical complaints and altered brain asymmetry in cerebral control of neuroendocrine activity.

Alterations of neuroendocrine brain asymmetry: a neural risk factor affecting physical health.

It was examined whether the specific pattern of brain asymmetry in cerebral control of cortisol secretion existing in a specific individual is suitable to predict the individual's physical health status. Results indicate that subjects with an altered, strong left hemisphere dominance of cortisol regulation show a clearly higher amount of physical complaints than subjects with a normal, strong right hemisphere dominance. In addition, results suggest that the subjects' specific pattern of neuroendocrine brain asymmetry can be used with relatively good success to separate individuals with high versus low degrees of physical complaints and thus, probably, to predict physical complaints of an individual.

Topographic brain mapping of emotion-related hemisphere asymmetries.

The study used topographic brain mapping of visual evoked potentials to investigate emotion-related hemisphere asymmetries. The stimulus material consisted of color photographs of human faces, grouped into two emotion-related categories: normal faces (neutral stimuli) and faces deformed by dermatological diseases (emotional stimuli). The pictures were presented tachistoscopically to 20 adult right-handed subjects. Brain activity was recorded by 30 EEG electrodes with linked ears as reference. The waveforms were averaged separately with respect to each of the two stimulus conditions. Statistical analysis by means of significance probability mapping revealed significant differences between stimulus conditions for two periods of time, indicating right hemisphere superiority in emotion-related processing. The results are discussed in terms of a 2-stage-model of emotional processing in the cerebral hemispheres.

Neuroendocrine hemisphere asymmetries: salivary cortisol secretion during lateralized viewing of emotion-related and neutral films.

The study set out to examine whether the cerebral hemispheres differ in their ability to regulate cortisol secretion during emotion-related situations. One hundred twenty-three adult subjects were shown either an emotionally aversive or a neutral film in the left or right hemisphere by means of a technique for lateralizing visual input that allows prolonged viewing while permitting free ocular scanning. The film-related changes of cortisol secretion were determined by salivary cortisol radioimmunoassay. Right hemispheric viewing of the emotionally aversive film resulted in a significantly higher increase of cortisol secretion than left hemispheric viewing of the same film. No such differences were observed with respect to the neutral film. Comparing the effects of the two films separately for each hemisphere revealed that only the right hemisphere was able to respond neuroendocrinologically in a different manner to the emotional and the neutral film. Therefore, it is concluded that cortical regulation of cortisol secretion in emotion-related situations is under primary control of the right hemisphere. The potential implications of asymmetric control of cortisol secretion with respect to the pathogenesis of psychosomatic and immunological disorders are discussed.

Psychophysiological correlates of human brain asymmetry: blood pressure changes during lateralized presentation of an emotionally laden film.

Fifty adult subjects were shown an emotionally positive film either in their left or right hemisphere by means of a technique for lateralizing visual input that allows prolonged viewing while permitting free ocular scanning. It was found that the cerebral hemispheres markedly differ in their capability to regulate blood pressure during emotionally laden situations of a distinctly positive nature. Right-hemispheric film presentation caused a significantly higher increase in systolic and diastolic pressure than left-hemispheric viewing of the same film. Moreover, hemisphere asymmetries were further increased if lateralized stimulus presentation and the lateralized carrying out of a stimulus-related response were combined within the same hemisphere, thereby enhancing unilateral processing. Finally, males and females clearly differed with respect to interhemispheric regulation of blood pressure.