Long-Range Respiratory and Theta Oscillation Networks Depend on Spatial Sensory Context

Area of Science:

• Neuroscience
• Systems Neuroscience
• Computational Neuroscience

Background:

• Neural oscillations facilitate communication between brain networks, particularly at lower frequencies.
• The nasal respiratory rhythm influences brain oscillations and is linked to memory, locomotion, and exploration.
• The piriform cortex is suspected to propagate respiratory rhythms, but its role alongside hippocampal theta during exploration is unclear.

Purpose of the Study:

• To investigate systemwide neural interactions during foraging behavior, focusing on the interplay between nasal respiratory rhythm and hippocampal theta.
• To determine how olfactory and visual spatial cues affect network connectivity and oscillatory coupling.
• To elucidate the role of the piriform cortex in integrating respiratory and theta rhythms.

Main Methods:

• Simultaneous recording of local field potentials from olfactory bulb, piriform cortex, hippocampus (dentate gyrus and CA1), and primary visual cortex in male rats.
• Recording of nasal respiration during foraging behavior using visual or olfactory spatial cues.
• Analysis of neural coherence, functional connectivity, and cross-frequency coupling between brain regions and respiratory rhythm.

Main Results:

• Increased network coherence during foraging compared to home cage activity, matching slow and fast respiratory rates.
• Piriform cortex and hippocampus showed strong theta-frequency coupling during slow respiration; other pairs coupled only at fast respiratory frequencies.
• Sensory cue modality influenced network interactions, with primary sensory areas showing greater impact.
• Respiratory and theta rhythms coupled with faster oscillations in sensory and hippocampal areas.

Conclusions:

• First evidence of widespread interactions between nasal respiration, olfactory bulb, piriform cortex, and hippocampus in awake, freely moving rats.
• The piriform cortex acts as an integrator of respiratory and theta activity.
• Network connectivity patterns are dynamic, changing with behavioral states and sensory input, with significant bidirectional interactions between olfactory and hippocampal systems.