Precise and Pervasive Phasic Bursting in Locus Coeruleus during Maternal Behavior in Mice

Area of Science:

• Neuroscience
• Behavioral Biology
• Neurochemistry

Background:

• The locus coeruleus (LC) is crucial for arousal, memory, and cognition, but its role in naturalistic social behavior is not well understood.
• LC activity is believed to multiplex signals through sustained (tonic) and burst (phasic) firing patterns, influencing brain states and discrete events.
• Noradrenaline (NA) system manipulation impairs social behavior, yet the precise temporal dynamics of LC firing during social interactions remain unknown.

Purpose of the Study:

• To investigate the temporal structure of LC neural activity during naturalistic social interactions in freely behaving mice.
• To determine if LC firing patterns (tonic and phasic) correlate with specific social behaviors, such as pup retrieval and maternal care.
• To elucidate the role of LC-mediated noradrenaline release in coordinating social actions and signaling behavioral states.

Main Methods:

• Chronic in vivo electrophysiology and fiber photometry were employed to record single-unit and population activity in the mouse LC.
• Neural activity was measured during spontaneous interactions between female mice and their pups.
• LC activity was correlated with specific behavioral events, including pup retrieval, nest building, and grooming.

Main Results:

• Pup retrieval elicited highly precise and reliable phasic bursts of LC activity, not attributable to simple sensory or motor factors.
• These phasic LC events were strongly correlated with specific subsequent behaviors, suggesting a role in action selection.
• Sustained maternal behaviors like nest building and grooming were associated with slow fluctuations in tonic LC firing rates.

Conclusions:

• The LC utilizes precisely timed phasic noradrenaline (NA) bursts to signal behaviorally significant social events, potentially coordinating brain-wide NA release.
• Slower changes in tonic LC firing reflect evolving behavioral states during sustained social interactions, such as maternal care.
• The LC plays a dual role in social behavior: guiding goal-directed action selection via phasic signaling and indicating internal states via tonic modulation.