The circadian system has evolved to benefit the fitness of the organism. A properly functioning clock improves overall performance and promotes health. By gaining more knowledge about how the... Show moreThe circadian system has evolved to benefit the fitness of the organism. A properly functioning clock improves overall performance and promotes health. By gaining more knowledge about how the system works and responds to changes, therapies can be developed to promote the functioning of the circadian system. In this thesis, the response of the circadian system to changes in daylength (e.g. long summer days and short winter days was investigated. In addition the functioning of the circadian system with aging was investigated. This is relevant since aging is known to be accompanied by a weakening of the circadian system in humans, which has been associated with deterioration of a number of age-related conditions such as arteriosclerosis, type 2 diabetes and neurodegenerative diseases such as Parkinson's and Alzheimer's disease. In addition, a large proportion of the elderly will experience fragmentation of sleep, meaning that people have difficulty sleeping at night, while during the day they are very sleepy. Promoting the circadian rhythm with relatively simple interventions, such as correctly timed exposure to (day) light, physical activity and food intake can support the circadian system and promote general health. Show less
The biological clock in mammals is located in the suprachiasmatic nucleus (SCN) and regulates daily and seasonal rhythms. The research presented in this thesis consists of behavioral and... Show moreThe biological clock in mammals is located in the suprachiasmatic nucleus (SCN) and regulates daily and seasonal rhythms. The research presented in this thesis consists of behavioral and electrophysiological experiments to investigate the SCN as a pacemaker of daily and seasonal rhythms. We investigated the activity of single neurons and small groups of neurons in the SCN and their role in photoperiodic adaptations. We found that single cells in the SCN do not code for the length of day, but that photoperiodic encoding is a property of the SCN neuronal network. Show less
