Understanding and Enhancing the Therapeutic Function of Sleep

Memories of intense, traumatic and unpleasant experiences are hard to forget. This persistence of so called 'emotional memories' is typically beneficial as it allows us to reflect on significant personal events and respond to future challenges effectively. However, if negative thoughts and experiences dominate our everyday lives, as is the case in major depression, then emotional memories can engulf our autobiographical histories, creating a chronic state of anxiety. Research suggests that sleep is crucial for emotional memory management. Restricted sleep impairs memory performance and psychological stability in healthy adults, while sleep disturbances are commonplace in major depression, affecting up to 90% of patients. A full understanding of the relationship between sleep, memory and emotion is therefore vital for gaining scientific insights into the mind, learning more about the fundamental biology of mental health and disease, and identifying innovative targets for therapeutic intervention. This research project will systematically investigate the role of sleep in emotional memory management. I will combine experimental psychology, cognitive neuroscience and neurophysiology to understand the mechanisms by which the sleeping brain processes memories of emotional experiences. To optimise the associated, scientific and medical benefits, the planned experiments will involve both healthy adults and patients with major depression. The starting point is to determine the necessity of sleep for emotional memory management. I will first compare the effects of sleep and sleep deprivation on emotional memory retention, physiological arousal and functional responses in emotional centres of the brain. Importantly, sleep consists of various stages, which each have distinct patterns of brain activity. Therefore, the second step will assess how boosting brain activity in different stages of sleep (via auditory stimulation) influences emotional memory. The third step is concerned with gaining deeper insights into the underlying mechanisms of the brain's emotional memory system. As such, I will use sophisticated brain imaging techniques to examine real-time changes in brain activity as emotional memories are reactivated in sleep. The transition of scientific research from bench to bedside is contingent on tangible benefits in clinical patients. Therefore, the fourth step will be to evaluate the effects of boosting sleeping brain activity on emotional memory management in patients with major depression. This will offer new headway in disentangling the links between chronic sleep disturbances and emotional memory impairments in psychiatric conditions, and may lay the groundwork for innovative therapeutic interventions. This research programme has strong potential to generate many societal benefits, both nationally and internationally. The World Health Organisation estimates that there are upwards of 350 million people worldwide suffering from a depressive mood disorder. Better understanding of the role of sleep in emotional memory may lead to new treatments, preventative strategies and diagnostic tools for major depression, potentially reducing the £105 billion annual economic cost of mental illness in England alone. Furthermore, enhancing knowledge of the mechanisms by which sleep supports learning and memory may lead to the development of novel educational aids for adults and children. Importantly, this research will raise public awareness of the value of sleep for memory and psychological stability, translating into better sleep practices and improved health and wellbeing.