Sharp Waves, Bursts, and Coherence: Activity in a Songbird Vocal Circuit Is Influenced by Behavioral State

Area of Science:

• Neuroscience
• Animal Behavior
• Bioacoustics

Background:

• Vocal learning in songbirds, like motor skill learning in mammals, involves the anterior forebrain pathway (AFP), a circuit analogous to the basal ganglia-thalamocortical system.
• While AFP neural activity during singing is well-studied, its dynamics during other behavioral states, particularly sleep, remain largely unknown.

Purpose of the Study:

• To investigate spontaneous neural activity patterns within the songbird AFP during natural sleep and awake states.
• To characterize the nature of neural bursts observed during sleep and compare them to known neural phenomena in other species.
• To examine functional connectivity within the AFP across different behavioral states.

Main Methods:

• Utilized chronically implanted Neuropixels probes for high-resolution neural recordings in male zebra finches.
• Recorded spontaneous neural activity and local field potentials (LFPs) during natural sleep and awake periods.
• Analyzed population bursts, LFP characteristics (sharp deflections, gamma power), and pairwise LFP coherence within the AFP.

Main Results:

• Identified synchronized population bursts in the LMAN region of the AFP during sleep, primarily during non-rapid eye movement sleep.
• These LMAN bursts were associated with negative sharp LFP deflections and transient increases in gamma power, resembling sharp-wave ripple activity in rodents.
• Observed increased delta and theta band coherence within LMAN and Area X during sleep compared to awake states.
• Found limited coherence between LMAN and Area X during sleep, suggesting spatially restricted input from LMAN to Area X.

Conclusions:

• This study provides the first detailed description of spontaneous neural dynamics in the songbird AFP across different behavioral states, including sleep.
• The observed LMAN population bursts during sleep suggest a potential role in memory consolidation or neural replay, analogous to hippocampal sharp-wave ripples.
• Findings on AFP functional connectivity during sleep offer new insights into information processing within this critical circuit for vocal learning.