Pupil fluctuations track rapid changes in adrenergic and cholinergic activity in cortex

Area of Science:

• Neuroscience
• Cognitive Science
• Physiology

Background:

• Cortical state fluctuations during wakefulness impact neural and behavioral responses.
• Pupil size variations are closely linked to these cortical state changes across species.
• The underlying physiological mechanisms remain largely unknown.

Purpose of the Study:

• To investigate the physiological processes connecting cortical state and pupil size variations.
• To identify the neuromodulatory systems involved in rapid pupil changes during wakefulness.

Main Methods:

• Recording pupil size and neuronal activity simultaneously in freely moving subjects.
• Analyzing correlations between pupil dynamics and activity in specific neuromodulatory projections.

Main Results:

• Rapid pupil dilations correlate with phasic activity in noradrenergic projections.
• Sustained pupil dilations, like during locomotion, associate with sustained cholinergic axon activity.
• Pupil size serves as a sensitive indicator of neuromodulatory system activity.

Conclusions:

• Neuromodulatory systems, specifically noradrenergic and cholinergic projections, play a critical role in regulating cortical state and pupil size during wakefulness.
• The pupil's dynamic changes offer a non-invasive window into the activity of these key brain systems.
• This research provides a novel method for tracking brain state control by neuromodulators.