Key mechanisms for setting the input-output gain across the motoneuron pool

Prog Brain Res. 2004;143:77-95. doi: 10.1016/s0079-6123(03)43008-2.

Abstract

This chapter summarizes a number of factors that control the "input-output" function across the motoneurons (MNs) comprising a single spinal motor nucleus. The main focus is on intrinsic properties of individual MNs that can be controlled by neuromodulators. These include: (1) amplification of the synaptic input at the cell's dendritic level by voltage-gated, persistent inward currents (plateau potentials); and (2) transduction of the net synaptic excitation into a frequency code (the MN's stimulus current-spike frequency relation) at the cell's soma/initial segment. Two other aspects of the synaptic control of MNs, which may affect their input-output gain, are also discussed. They include the hypotheses that: (1) a non-uniform distribution of synaptic effects to low- and high-threshold motor units causes a change in recruitment gain; and (2) recurrent inhibition, via motor axon collaterals and Renshaw cells, functions as a variable gain regulator of MN discharge.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Action Potentials
  • Afferent Pathways / physiology
  • Animals
  • Efferent Pathways / physiology
  • Electric Conductivity
  • Motor Neurons / physiology*
  • Recruitment, Neurophysiological
  • Spinal Cord / cytology
  • Spinal Cord / physiology*
  • Synapses / physiology