Activity-dependent feedforward inhibition modulates synaptic transmission in a spinal locomotor network

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• Neural network analysis traditionally focuses on individual synapses.
• Understanding how neural assemblies emerge from neuronal connectivity and function is limited.

Purpose of the Study:

• To investigate synaptic properties within the lamprey locomotor network.
• To elucidate the role of excitatory network interneurons (EINs) in shaping motor neuron activity.

Main Methods:

• Analysis of synaptic properties in the lamprey locomotor network.
• Electrophysiological recordings to study neuronal connectivity and synaptic transmission.
• Investigation of activity-dependent synaptic facilitation and depression.

Main Results:

• A proportion of EINs evoke activity-dependent disynaptic feedforward inhibition in motor neurons via inhibitory interneurons.
• Both synapses in the disynaptic pathway show activity-dependent facilitation.
• EINs can also evoke feedforward excitation in motor neurons, which typically depresses during spike trains.
• Feedforward inhibition heterosynaptically depresses direct excitatory inputs to motor neurons.

Conclusions:

• Activity-dependent heterosynaptic effects within neuronal assemblies modulate synaptic integration in motor neurons.
• These mechanisms contribute to the delayed development of feedforward inhibition and may terminate motor neuron spiking.