Output variability across animals and levels in a motor system

Area of Science:

• Neuroscience
• Systems Biology
• Biophysics

Background:

• Rhythmic behaviors exhibit significant individual variability.
• Understanding the sources of this variability, from neural circuits to the motor periphery, is crucial.
• The leech heartbeat system provides a model for studying motor output variability.

Purpose of the Study:

• To investigate the sources of output variability in a rhythmic motor system.
• To differentiate variability contributions from the central pattern generator (CPG) and the motor plant.
• To analyze coordination-specific variability in intersegmental phase relations (Δϕ).

Main Methods:

• Analysis of the bilaterally symmetric leech heartbeat system.
• Examination of central pattern generator (CPG) and motor neuron activity.
• Quantification of intersegmental phase relations (Δϕ) within and between coordinations.

Main Results:

• The leech heartbeat system demonstrates high precision within a coordination.
• Variability in repetitions of a coordination contributes minimally to population output variability.
• Differences between bilaterally homologous cells and individual genetic/life history factors significantly contribute to output variability.
• Variability of Δϕ was coordination-specific, with some showing significant reduction from CPG to motor pattern.

Conclusions:

• Motor pattern generation in the leech is precise within a coordination.
• While CPGs contribute to rhythmic behavior, downstream mechanisms play a role in modulating output variability.
• Genetic and life history differences among individuals are likely major drivers of population-level variability in rhythmic behaviors.