Recurring Cholinergic Inputs Induce Local Hippocampal Plasticity through Feedforward Disinhibition

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Computational Neuroscience

Background:

• Local circuitry in the hippocampus involves diverse interneurons regulating excitatory synaptic plasticity.
• The role of interneurons in cholinergic modulation of synaptic plasticity is not fully understood.

Purpose of the Study:

• To elucidate the mechanisms by which cholinergic activation of OLMα2 interneurons induces long-term potentiation (LTP) at Schaffer collateral (SC)-CA1 synapses.
• To investigate the role of disinhibition and precise timing in cholinergic-induced hippocampal plasticity.

Main Methods:

• Combined in vitro experimental studies with biophysically based computational modeling.
• Investigated the effects of cholinergic activation of α7 nAChRs on OLMα2 interneurons and their impact on feedforward inhibition.

Main Results:

• Model suggests α7 nAChR activation enhances OLM GABAergic activity, inhibiting fast-spiking interneurons.
• This disinhibition, coupled with timed SC stimulation, leads to potentiation at SC-CA1 synapses.
• Identified critical timing windows between disinhibition and stimulation for inducing plasticity.

Conclusions:

• Cholinergic neuromodulation of feedforward disinhibitory circuits is key to regulating hippocampal plasticity.
• Activation of α7 nAChRs on OLM interneurons, when precisely timed with SC stimulation, enables SC-CA1 synapse potentiation via disinhibition.
• Highlights the intricate interplay between inhibitory circuitry and cholinergic signaling in hippocampal network function and plasticity.