“Citius, Altius, Fortius” the impact of circadian phenotype and sleep on the brain’s intrinsic functional architecture, well-being & performance

Abstract

A major challenge facing our rapidly developing ‘round the clock’ society is in understanding how disruptions to sleep and endogenously driven biological clocks influence many aspects of our lives. This thesis combines the fields of chronobiology, sleep and neuroimaging to investigate the impact of Circadian Phenotype and time of day on the brain’s intrinsic architecture (using functional MRI), well-being and performance. Brain function changes during wakefulness and sleep, as well as in a range of neurological and psychiatric disorders. The results show, for the first time, clear differences in intrinsic functional architecture between Early and Late Circadian Phenotypes (ECP/LCP), as well as variations depending on the time of day. In general, ECPs have higher functional connectivity than LCPs to the majority of regions identified, and these differences can predict better outcomes in cognitive and physical performance measures. Performance also shows significant diurnal variations within Circadian Phenotypes. A wider investigation in the LCP group showed that a phase advance in a real world setting using non-pharmacological interventions has a positive impact on mental well-being and performance. In summary, this thesis supports the need to consider both Circadian Phenotype and time of day in neuroimaging and performance research. It also highlights that chronic disruptions often associated with LCPs could have intrinsic neural origins. Furthermore, it provides a novel intervention strategy for LCPs to enhance well-being and performance during a societal constrained day. These findings could have significant implications in clinical, research and real world settings