Experimental Brain Research

, Volume 236, Issue 10, pp 2611–2618 | Cite as

Properties of short-latency responses in the upper limbs evoked by axial impulses during leaning: evidence for reticulospinal projections

  • Niroshan Jeyakumar
  • Sendhil Govender
  • James G. ColebatchEmail author
Research Article


We studied the short-latency (SL) effects of postural perturbations produced by impulses applied over the spine of the C7 vertebra or the sternum (“axial impulses”) in 12 healthy subjects. EMG recordings were made bilaterally from the triceps brachii, biceps brachii, soleus, and tibialis anterior muscles, and unilaterally from the deltoid, forearm flexors, forearm extensors, and first dorsal interosseous (FDI) muscles. Sternal impulses evoked short-latency responses in the biceps when subjects leaned posteriorly to support approximately 12% of their body weight with the arms, but these responses were only modestly larger than for isometric contraction of the arms (26.3 vs. 14.7%). In contrast, clear excitatory responses could be evoked in the deltoid, triceps, forearm muscles, and FDI when leaning anteriorly to support similar amounts of body weight. These responses were significantly larger than during isometric contraction. The deltoid (42.5%) and triceps (44.7%) had the largest responses in supported anterior lean and onset latencies increased distally in this condition (mean 31.8 ms in deltoid to 53.7 ms in FDI). There was a disproportionate delay between the forearm muscles and FDI. For both directions of lean, postural reflex responses normally present in the legs were severely attenuated. SL upper limb excitatory responses were bigger in proximal muscles as well as larger and more widespread for anterior axial perturbations compared to posterior axial perturbations when using the arms to support body weight. Our findings also provide further evidence of a role for reticulospinal pathways in mediating these rapid postural responses to accelerations of the trunk.


Postural reflexes Upper limbs Reticulospinal 


Compliance with ethical standards

Conflict of interest

No conflicts of interest, financial or otherwise, are declared by the authors.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • Niroshan Jeyakumar
    • 1
  • Sendhil Govender
    • 1
  • James G. Colebatch
    • 1
    • 2
    Email author
  1. 1.Prince of Wales Clinical School and Neuroscience Research AustraliaUniversity of New South WalesSydneyAustralia
  2. 2.Institute of Neurological SciencesPrince of Wales HospitalSydneyAustralia

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