Reciprocal interactions between CA1 pyramidal and axo-axonic cells control sharp wave-ripple events

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• Inhibition is crucial for neural circuit function and timing of cell assembly spiking.
• Hippocampal sharp wave-ripples (SPW-Rs) are network events organized by excitation-inhibition balance.
• The precise role of specific inhibitory interneurons, like axo-axonic cells (AACs), in SPW-Rs is not fully understood.

Purpose of the Study:

• To investigate the role of axo-axonic cells (AACs) in modulating hippocampal sharp wave-ripples (SPW-Rs).
• To clarify the impact of AAC activity on pyramidal cell (PYR) spiking and network dynamics during SPW-Rs.

Main Methods:

• Optogenetic tagging and manipulation of AACs in behaving mice.
• Silicon probe recordings to monitor neuronal activity and SPW-Rs.
• Analysis of AAC spiking variability and their input from PYR assemblies.

Main Results:

• AACs exhibited diverse spiking patterns during SPW-Rs, unlike other parvalbumin-expressing interneurons.
• AACs received convergent inputs from local PYR assemblies, influencing their SPW-R participation.
• Optogenetic silencing of AACs prolonged SPW-Rs and increased PYR recruitment, indicating AACs regulate SPW-R dynamics.

Conclusions:

• AACs play a significant role in controlling the dynamics and extent of hippocampal SPW-Rs.
• Reciprocal interactions between PYRs and AACs may organize cell assemblies during SPW-Rs via lateral inhibition.