Toward a computational role for locus coeruleus/norepinephrine arousal systems

Brain and behavior undergo measurable changes in their underlying state, and neuromodulators are thought to contribute to these fluctuations. Why do we undergo such changes, and what function could the underlying neuromodulatory systems perform? Here, we examine theoretical answers to these questions with respect to the locus coeruleus/norepinephrine system, focusing on peripheral markers for arousal, such as pupil diameter, which are thought to provide a window into brain-wide noradrenergic signaling. We explore a computational role for arousal systems in facilitating internal state transitions that facilitate credit assignment and promote accurate perceptions in nonstationary environments. We summarize recent work supporting this idea and highlight open questions, as well as alternative views of how arousal affects cognition.