Neuromodulation Enables Temperature Robustness and Coupling Between Fast and Slow Oscillator Circuits

Area of Science:

• Neuroscience
• Systems Neuroscience
• Computational Neuroscience

Background:

• Neuronal circuits must maintain function across varying environmental temperatures for survival.
• Rhythmic neuronal circuits in the crustacean stomatogastric ganglion (STG) exhibit remarkable temperature robustness, but the underlying mechanisms are not fully understood.

Purpose of the Study:

• To investigate how rhythmic neuronal circuits in the STG achieve temperature robustness.
• To differentiate temperature effects on intrinsic rhythm generators from extrinsic modulatory inputs.

Main Methods:

• Dissociated temperature manipulations of STG rhythm generators and upstream ganglia.
• Electrophysiological recordings to monitor circuit activity and rhythm generation.
• Investigated the role of the peptidergic modulatory projection neuron (MCN1) and its neuropeptide transmitter.

Main Results:

• The slow gastric mill rhythm's temperature robustness relies on heat-activated factors extrinsic to the STG, while the fast pyloric rhythm's response is partly modulated by these factors.
• Heating upstream ganglia and temperature-matching them to the STG restored a crashed gastric mill rhythm and increased MCN1 activity.
• MCN1's neuropeptide transmitter stabilized the gastric mill rhythm across a broad temperature range.
• Integer coupling between pyloric and gastric mill rhythms was intrinsically robust to temperature changes, independent of extrinsic inputs.

Conclusions:

• Extrinsic neuromodulation is crucial for the temperature robustness of STG oscillatory circuits, enabling neural function under thermal stress.
• Intrinsic properties of rhythm generators confer temperature robustness to the coupling between rhythms.
• Degenerate circuit properties can lead to idiosyncratic responses to environmental challenges like extreme temperatures.