Place cell assemblies remain intact, despite reduced phase precession, after cholinergic disruption

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• The hippocampal theta rhythm is hypothesized to act as a neural clock, coordinating neuronal firing for memory formation.
• Phase precession, a temporal coding mechanism, is thought to reflect this clocking function and is impaired by cholinergic disruption.
• It remains unclear if hippocampal neural assemblies, crucial for coherent neural activity, are also degraded when cholinergic signaling is disrupted.

Purpose of the Study:

• To investigate whether hippocampal neural assemblies are degraded following systemic cholinergic disruption.
• To test the hypothesis that intact cholinergic signaling and high-quality phase precession are necessary for maintaining neural assembly integrity.

Main Methods:

• Recorded spiking activity of hippocampal place cells in rats navigating a circular track.
• Administered a muscarinic acetylcholine receptor antagonist to disrupt cholinergic signaling.
• Analyzed neural assembly integrity using cross-correlogram analysis, general linear model-based prediction, and population activity reconstruction.

Main Results:

• Systemic cholinergic disruption did not degrade the integrity of hippocampal place cell assemblies.
• Cross-correlogram analyses showed no loss of spike-timing reliability between cell pairs.
• Predictive analyses and environmental reconstruction revealed no impairment in assembly function or information coding.

Conclusions:

• Hippocampal neural assemblies maintain their integrity despite impaired cholinergic signaling and degraded phase precession.
• These findings challenge the necessity of high-fidelity phase precession for the formation and stability of hippocampal neural assemblies.
• Place cell assembly function is robust and does not strictly depend on the theta rhythm's precise clocking mechanism.