The limbic system – emotion regulation
Basic emotional states like fear and reward are processed via neural circuits in the brain. Scientists of the project FEARREWARDCIRCUITS (Circuit mechanisms of fear vs. reward in the limbic system) investigated the underlying mechanisms using Pavlovian fear and reward conditioning in mice models. Project researchers developed novel behavioural protocols to induce positive and negative emotional states in mice. After learning from a reward conditioning task, the mice underwent a fear conditioning task. Scientists then assessed their emotional responses and arousal for different tasks using corticosterone levels and global brain mapping as a measure. Results indicated similar elevation in corticosterone levels as well as a high-activation of the bed nucleus of stria terminalis (BNST) in the brain during fear and reward conditioning tasks. Given the known role of the amygdala in emotional activity and the fact that BNST receives signals from the basolateral amygdala (BLA), researchers optogenetically manipulated BLA-to-BNST activity. They found decreased expression of fear and reward upon BLA-to-BNST activation, indicating the role of this circuit in encoding arousal. Further studies are being carried out using fluorescent proteins called "timer" that change colour with time after cellular activation. Results are expected to pinpoint the neuronal populations activated by fear and reward within the amygdala-BNST circuits. Resolving emotion regulation could find applications in treatment behavioural including anxiety, eating disorders and addictions. Protocols can be adapted and extended to investigate other brain functions.
Keywords
Limbic, emotion, behavioural disorder, fear, reward, Pavlovian conditioning, BNST, amygdala
