| Numerous psychological and physiological functions are affected by a circadian mechanism, also referred to as 'the biological clock'. The essence of this project inquires the existence of a circadian modulation of activity, reactivity and the interdependency of those functions that are involved in the stressresponse. This hypothesis will be examined with the use of a 24-hour registration protocol (constant routine) in which activity levels and activity patterns of sympathovagal, endocrine, and immunological variables will be monitored in relation to the cardiovascular stressresponse to brief series of stressors. These stressors will be presented repeatedly during a constant routine procedure, in order to monitor the endogenous circadian rhythm unmodified by external influences. Prior to the constant routine, ambulant cardiographic measurements and sleepregistrations will be measured. The subjectpool contains 40 morningtypes and 40 eveningtypes, selected by a questionnaire. This project intends to formulate standard values regarding circadian rhythms and stress reactivity. Furthermore, ambulantory measurements will provide insights on the coherence between the endogenous and exogenous sources of 24-hour variations. The sleepregistrations will offer information about the relation between the various sleepstages and cardiovascular functioning, revealing the sympathovagal regulation during these sleepstages. |
