Some differences in the nature of circadian changes of activation

Abstract

The aim of this investigation was to find out some physiological correlates of activation self-assessment, and to try to establish whether different mechanisms (oscillators) are involved in circadian changes of some psychophysiological variables. The investigation included 32 subjects (students) aged 19-23 years. During 24-hours measurements of body temperature, pulse rate, blood pressure, and activation, assessment were taken hourly. The circadian changes of most observed variables showed significant inter-correlations, but phase differences as well. Factor analysis of the results showed the existence of two independent factors, which together with the observed differences in the phases and periods of the changes indicated the existence of two separate oscillators. One o f them seemed to control the general activation factor, which saturated body temperature, pulse rate and systolic blood pressure. The oilier oscillator, however, controlled the changes in high activation, i.e. stress level. The results support some earlier studies which indicated multioscillatory control of circadian changes in some psychophysiological variables.