Spinal Network Development


This article is a review of research into the development of the spinal networks that control rhythmic locomotor movements. By the time they reach adulthood, most animals display a complex repertoire of characteristic motor behaviours that are essential for their survival. One such behaviour is locomotion, which involves rhythmically repeating movements of the body or appendages, produced by the coordinated contractions of different skeletal muscle groups. Muscle contractions are generated by bursts of action potentials in motorneurons (MNs) whose firing patterns are controlled by networks of interneurons that reside principally in the spinal cord and hindbrain. This article provides an overview of current knowledge on the development of the neuronal networks that control locomotion.

Key Concepts:

  • Locomotion in vertebrates involves rhythmic contractions of functionally antagonistic pairs of muscles.

  • The locomotor rhythm is generated by networks of neurons in the central nervous system, often called central pattern generators (CPGs).

  • The neural networks responsible for locomotion arise early in vertebrate development, often before birth or hatching.

  • Locomotor network development precedes the emergence of the behaviours the networks will eventually control.

  • Neural mechanisms for locomotor rhythm generation appear to be similar across a range of species.

  • The basic rhythm is generated by glutamate‐mediated excitation and glycine‐mediated inhibition.

  • The motor output generated by immature locomotor networks often lacks the flexibility required of adult behaviour.

  • During locomotor network maturation there is a sequence of changes in the properties of and connections between spinal neurons.

  • During development, locomotor networks are progressively influenced by neuromodulatory systems, many of which originate from nuclei in the brainstem.

  • Serotonin released from neurons of the raphe nuclei in the brainstem appears to be a particularly important neuromodulator.

  • The way in which additional components are added sequentially to locomotor networks in different species ensures the motor output matches the development stage‐specific behavioural requirements of the host organism.

Keywords: motor control; spinal cord; locomotion; development; rhythm generation; neuromodulation; CPG; neural network; metamorphosis; motorneuron


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Further Reading

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Sillar KT, Combes D, Ramanathan S, Molinari M and Simmers J (2008) Neuromodulation and developmental plasticity in the locomotor system of anuran amphibians during metamorphosis. Brain Research Review 57: 94–102.

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Sillar, Keith T, and McLean, David L(Jun 2010) Spinal Network Development. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0000834.pub2]