Norepinephrine, a neuromodulator released during times of stress and arousal, is implicated in neuronal plasticity, memory consolidation and cognitive functions, including decision-making and behavioral flexibility. The brainstem nucleus locus coeruleus (LC) is the major source of forebrain norepinephrine. We recorded optogenetically identified LC neuronal activity in rats performing at their own pace in a fully automated T-maze for liquid rewards. First they had to choose the reward arm on the basis of visual cues, then new spatial reward contingencies were imposed. In the session where the animal shifted tasks the first time, the LC firing rate after VC onset increased significantly, even as the animal adhered to the previous rule. Firing rate also increased prior to crossing photodetectors that controlled stimulus onset and offset, and this was positively correlated with accelerations, consistent with a role in mobilizing effort. The results contribute to the growing evidence that the LC is essential for behavioral adaptation by promoting cognitive flexibility and mobilizing effort in face of changing environmental contingencies.
L. Xiang, A. Harel, HY. Gao, AE. Pickering, SJ. Sara, SI. Wiener (2019). Scientific Reports 9:1361.