What Most people know how it feels to be sick. The sickness response includes fatigue, changes in sleep pattern, lack of interest in daily activities, decreases in appetite, weight loss, and unspecific pain. This is believed to be beneficial for survival of the individual and/or the species. By causing the sick individual to rest in a safe place and not search for food, it maximizes chance of survival and minimizes disease spread. Excessive sleepiness and anorexia will however become problematic after a while, and for this reason the brain needs to balance behaviors during sickness to optimize survival. My project aims to understand the basic biological mechanisms of how activation of the immune system affects the brain and its homeostatic regulation of rest and activity. Why Symptoms of sickness such as sleepiness is the primary patient concern in many diseases as diverse as brain trauma, infection, various cancers, inflammatory and autoimmune diseases. In chronic/long lasting disorders, sickness behavior no longer aids recovery, but can none the less still be present and markedly reduce quality of life and work ability among the patients. Tackling this societal challenge starts with a better understanding of the basic biological principles of the neuronal response to an activated immune system, and our hope is to eventually develop a better treatment for excessive daytime sleepiness in cronically ill patients. How We will study sick and healthy mice and measure their behavioural response to immune activation. We will also examine the brains and determine what neuronal pathways becomes activated following immune activation. We will quantify both short- and long-term effects. SSR Once we understand how activation of the immune system affects brain function, we will be able to devise targeted treatment for excessive sickness response in a range of chronic diseases to increase quality of life and work ability among patients.