What is the relationship between neuromodulators (chemicals that allow and regulate communication between nerve cells) such as norepinephrine (NE), stressful experience and how we learn about what is painful and pleasurable in the world? Our past research has shown that individual differences in how emotion influences perception and memory can be partly explained by common genetic differences that influence NE activity in the brain. What we do not know is whether these differences in emotional bias are due to how quickly or intensely people learn emotional associations, or whether such emotional learning can be linked to differences in NE or in activity in the locus coeruleus (LC), the cluster of neurons in the brain stem that produces NE. Furthermore, our previous research has linked common genetic variations to negative emotional biases, but it is unclear if and how they influence the transfer of behaviours associated with appetitive stimuli such as rewards. Since appetitive biases have been linked to craving associated with addiction, this research will help to clarify whether genetic variations make people more vulnerable to addictive behaviours. Finally, we are interested in how stress influences emotional learning. In this research theme we are conducting a series of studies that employ genotyping and brain imaging (functional magnetic resonance imaging, or fMRI) and positron emissions tomography (PET) along with computational modeling, eye tracking, and behavioural measures to assess the role of LC/NE and stress in neural and behavioural measures of emotional learning. This will help us to understand how individual differences in neurochemical availability such as NE as well as dopamine and serotonin may lead to differences in emotional learning and how this may be altered in situations of acute stress. Thus, we hope to unravel why some people are more likely to develop addictive cravings for certain rewards such as food or alcohol and how this tendency may be enhanced in stressful situations.