What do the tonic and phasic modes of the locus coeruleus do to the cortex? · Grey Matter

In the phasic mode, moderate background firing is punctuated by brief bursts locked to task-relevant events, and the noradrenaline released then sharpens cortical responses to exactly those events.

What do the tonic and phasic modes of the locus coeruleus do to the cortex?

In the phasic mode, moderate background firing is punctuated by brief bursts locked to task-relevant events, and the noradrenaline released then sharpens cortical responses to exactly those events. In the high tonic mode, firing is steady and elevated, bursts fade, and behaviour becomes distractible and exploratory. The adaptive gain theory of Aston-Jones and Cohen proposes that the system switches between exploiting the current task and searching for alternatives this way. Because noradrenaline raises the gain and excitability of cortical circuits, sustained high tonic output also shifts the excitation-inhibition operating point toward easier firing.