Circuit feedback increases activity level of a circuit input through interactions with intrinsic properties

Area of Science:

• Neuroscience
• Motor Control
• Computational Neuroscience

Background:

• Central pattern generator (CPG) circuits generate rhythmic behaviors.
• CPG feedback influences projection neuron activity and circuit output.
• The regulation of projection neuron intraburst firing rates by CPG feedback is unknown.

Purpose of the Study:

• Investigate whether CPG feedback regulates projection neuron intraburst firing rates.
• Determine the conditions under which CPG feedback affects intraburst firing.
• Identify novel roles for CPG feedback in neural circuit function.

Main Methods:

• Used identified neurons in the stomatogastric nervous system of the crab, Cancer borealis.
• Studied projection neuron activity during a chewing rhythm elicited by mechanosensory input.
• Manipulated feedback pathways and modulatory inputs to assess effects on intraburst firing.

Main Results:

• CPG feedback increased intraburst firing rate in commissural projection neuron 2 (CPN2) under mechanosensory stimulation.
• This feedback effect was state-dependent, decreasing CPN2 intraburst firing under a different modulatory input.
• A specific feedback pathway induced postinhibitory rebound, enhancing CPN2 intraburst firing.

Conclusions:

• CPG feedback can dynamically regulate projection neuron intraburst firing rates.
• This regulation depends on interactions with intrinsic neuronal properties and modulatory state.
• CPG feedback plays a novel, state-dependent role in adjusting projection neuron activity levels.