Convergent Comodulation Reduces Interindividual Variability of Circuit Output.

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• Neural circuit output exhibits remarkable consistency across individuals despite variations in individual neuron properties.
• Neuromodulators influence neural circuit flexibility, often with overlapping actions but distinct receptor expression patterns.
• Convergent neuromodulation, where multiple signals act on common targets, may enhance uniformity in neural responses.

Purpose of the Study:

• To test the hypothesis that tonic comodulation by convergent neuromodulators reduces interindividual variability in neural circuit output.
• To investigate the role of neuromodulators in stabilizing neural network function.

Main Methods:

• Quantified interindividual variability of the pyloric circuit output in Cancer borealis (crabs) by measuring activity phases, cycle frequency, and spike characteristics.
• Examined the effect of different combinations and concentrations of three excitatory neuropeptides on circuit output variability.
• Assessed the impact of comodulation on the response variability of isolated neurons.

Main Results:

• Mid-level concentrations (30 nM) of comodulating neuropeptides significantly reduced pyloric circuit output variability.
• Near-threshold (1 nM) or saturating (1 µM) concentrations of neuropeptides did not reduce variability.
• Comodulation did not reduce the interindividual variability of isolated neuron responses, suggesting a network effect.

Conclusions:

• Tonic, non-saturating levels of comodulation by convergent neuromodulators can reduce interindividual variability in neural circuit output.
• The reduction in output variability appears to be an emergent network property, not attributable to effects on individual neurons.
• This finding highlights a potential mechanism for maintaining consistent behavior across individuals in biological systems.