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Movement-related receptive fields of spinal motoneurones with active dendrites. J Physiol 2008 Mar 15;586(6):1581-93

Date

02/02/2008

Pubmed ID

18238818

Pubmed Central ID

PMC2375694

DOI

10.1113/jphysiol.2007.149146

Scopus ID

2-s2.0-40949097674 (requires institutional sign-in at Scopus site)   30 Citations

Abstract

The primary control of spinal motoneurone excitability is mediated by descending monoaminergic systems, which have diffuse effects on multiple motor pools. Much of the sensory input evoked by movement is also distributed broadly to multiple joints. The muscle spindle Ia afferent system, however, is sharply focused, with Ia excitation restricted to close synergists and Ia reciprocal inhibition only shared between antagonists acting at a single joint. We studied the interaction of neuromodulatory and sensory inputs in determining the movement-related receptive field (MRRF) of motoneurones during passive joint movements of the cat hindlimb. In a decerebrate preparation with tonic monoaminergic input to the cord, the MRRFs tended to be focused for the ankle and knee extensor motor pools studied. Ankle rotation produced larger synaptic currents in ankle extensors than knee or hip rotations and knee rotation dominated input to the knee extensors. The persistent inward current (PIC) in motoneurone dendrites, which is facilitated by monoaminergic input, amplified the MRRF about 2-fold, consistent with its effects on other inputs. Acute spinal transaction markedly broadened MRRFs, with hip rotation generating large currents in both ankle and knee extensors. Spinalization also eliminated amplification of MRRFs, as expected from elimination of descending monoaminergic input. Ia reciprocal inhibition is very effective in suppressing dendritic PICs and thus provides a local and specific PIC control system to oppose the diffuse PIC facilitation from descending monoaminergic systems. The focused MRRF seen in the intact cord state would allow reciprocal inhibition to fulfil this role without undue interference from multijoint input from other afferent systems.

Author List

Hyngstrom A, Johnson M, Schuster J, Heckman CJ

Author

Allison Hyngstrom PhD Associate Professor in the Physical Therapy department at Marquette University




MESH terms used to index this publication - Major topics in bold

Action Potentials
Afferent Pathways
Animals
Cats
Dendrites
Efferent Pathways
Evoked Potentials, Motor
Feedback
Hindlimb
Motor Neurons
Movement
Nerve Net
Spinal Cord