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

Area of Science:

• Neuroscience
• Computational Neuroscience
• Cellular Neuroscience

Background:

• Inhibition regulates neural circuits and cell assembly spiking across timescales.
• In the hippocampus (CA1), excitation-inhibition balance shapes pyramidal cell (PYR) spike timing during network events like sharp wave-ripples (SPW-Rs).
• The precise sources of inhibition during SPW-Rs are unclear, with over 20 GABAergic interneuron types in CA1.

Purpose of the Study:

• To investigate the role of axo-axonic cells (AACs) in modulating SPW-Rs in behaving mice.
• To clarify the controversial impact of AAC activity on SPW-R dynamics.

Main Methods:

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

Main Results:

• AACs exhibited diverse spiking patterns during SPW-Rs, unlike other parvalbumin-expressing interneurons.
• AACs received convergent monosynaptic inputs from PYR cell assemblies.
• Optogenetic silencing of AACs led to increased SPW-R power and duration, recruiting more PYRs.

Conclusions:

• AACs play a significant role in controlling SPW-R dynamics.
• Reciprocal PYR-AAC interactions, involving lateral inhibition, may organize cell assemblies during SPW-Rs.