Experimental Brain Research

, Volume 203, Issue 2, pp 271–283

Measuring the motor output of the pontomedullary reticular formation in the monkey: do stimulus-triggered averaging and stimulus trains produce comparable results in the upper limbs?

  • Wendy J. Herbert
  • Adam G. Davidson
  • John A. Buford
Research Article

DOI: 10.1007/s00221-010-2231-5

Cite this article as:
Herbert, W.J., Davidson, A.G. & Buford, J.A. Exp Brain Res (2010) 203: 271. doi:10.1007/s00221-010-2231-5

Abstract

The pontomedullary reticular formation (PMRF) of the monkey produces motor outputs to both upper limbs. EMG effects evoked from stimulus-triggered averaging (StimulusTA) were compared with effects from stimulus trains to determine whether both stimulation methods produced comparable results. Flexor and extensor muscles of scapulothoracic, shoulder, elbow, and wrist joints were studied bilaterally in two male M. fascicularis monkeys trained to perform a bilateral reaching task. The frequency of facilitation versus suppression responses evoked in the muscles was compared between methods. Stimulus trains were more efficient (94% of PMRF sites) in producing responses than StimulusTA (55%), and stimulus trains evoked responses from more muscles per site than from StimulusTA. Facilitation (72%) was more common from stimulus trains than StimulusTA (39%). In the overall results, a bilateral reciprocal activation pattern of ipsilateral flexor and contralateral extensor facilitation was evident for StimulusTA and stimulus trains. When the comparison was restricted to cases where both methods produced a response in a given muscle from the same site, agreement was very high, at 80%. For the remaining 20%, discrepancies were accounted for mainly by facilitation from stimulus trains when StimulusTA produced suppression, which was in agreement with the under-representation of suppression in the stimulus train data as a whole. To the extent that the stimulus train method may favor transmission through polysynaptic pathways, these results suggest that polysynaptic pathways from the PMRF more often produce facilitation in muscles that would typically demonstrate suppression with StimulusTA.

Keywords

ReticulospinalElectromyographyElectrical stimulationReachingMacaque

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Wendy J. Herbert
    • 1
  • Adam G. Davidson
    • 2
    • 4
  • John A. Buford
    • 1
    • 2
    • 3
  1. 1.Division of Physical Therapy, School of Allied Medical ProfessionsThe Ohio State UniversityColumbusUSA
  2. 2.Neuroscience Graduate Studies ProgramThe Ohio State UniversityColumbusUSA
  3. 3.Center for Brain and Spinal Cord RepairThe Ohio State UniversityColumbusUSA
  4. 4.Department of Neurobiology and AnatomyUniversity of Rochester Medical CenterRochesterUSA