The relationship between thermoregulatory and haemodynamic responses of the skin to relaxation and stress

The present study investigated the effects of stress and relaxation on (1) EEG coherence and (2) peripheral blood flow. EEG coherence of two meditators in two different but adjacent rooms was measured during eyes opened, eyes closed, single meditation and group meditation. The skin temperatures of the subjects together with their room temperatures were also recorded. EEG coherence plots (Cospar) showed a spread out of the alpha band to the beta, theta and occasionally to the delta wave bands during group meditation. The area above the 0.98 coherence threshold in the alpha band was greater during group meditation than during single meditation and eyes closed. The peripheral blood flow study included measurement of arterial and venous blood volume, and temperature of the fingertips. Finger blood flow and temperature were measured by photoplethysmography and thermistor, respectively. The mean of the peak cross correlation between the blood volume and the temperature of the fingertips of the nine cases studied was 0.9236 ± 0.0408. The finger temperature closely followed that of the finger blood flow but at a slower rate. It was also observed that the finger blood flow and the temperature increased during eyes closed relaxation, but decreased during stressful state. Changes in venous blood volume (temperature), corresponded to changes in the amplitude of the arterial blood volume. Thus, during relaxation the finger arterioles are vasodilated, and during stress they are vasoconstricted