Crossed actions on group II‐activated interneurones in the midlumbar segments of the cat spinal cord.

Abstract

SUMMARY1. Evidence has been sought for crossed actions on midlumbar propriospinal neurones activated by ipsilateral group II muscle afferents, with particular emphasis on those neurones with projections to the ipsilateral hindlimb motor nuclei.2. A large majority of group II-activated midlumbar neurones were influenced by stimulation of contralateral group II afferents. The most frequent and most powerful actions were from those nerves which most effectively influenced ipsilateral midlumbar neurones. Crossed actions from group I afferents were rare.3. In the great majority of neurones the pattern of actions was similar from both limbs, the neurones being bilaterally excited, bilaterally inhibited or had both EPSPs and IPSPs from both sides.4. The latencies of crossed actions suggest that the earliest crossed EPSPs from group II afferents were evoked disynaptically (i.e. via a single commissural neurone) and that the crossed IPSPs were evoked trisynaptically.5. The pattern of crossed actions suggests a strong bilateral interaction between midlumbar neurones. The possible role of these neurones in postural control and the production of co-ordinated movements of the hindlimbs is discussed.

Interlimb Coordination During the Stance Phase of Gait in Subjects With Stroke

“…Considering that most midlumbar interneuron recipients from group II input are influenced by afferent fibres from both ipsilateral and contra-lateral sides 13 , a relation from ankle dorsiflexors during initial contact and loading response to contra-lateral knee extensors during pre swing could be expected.…”

“…Recent studies involving healthy subjects have demonstrated that the degree of plantar flexor activity during propulsion depends on the degree of muscle activity 9 and on the magnitude of the ground reaction force 10 of the contralateral limb during heel strike. This interlimb relation observed during step-to-step transition of unimpaired walking 9,10 , and also in standing-related tasks 11,12 , can be justified by the bilateral influence of group II fibres on spinal interneurons 13 and by the importance of vestibulo-and reticulo-spinal pathways on group II fibres 14 .…”

Differential Projections of Excitatory and Inhibitory Dorsal Horn Interneurons Relaying Information from Group II Muscle Afferents in the Cat Spinal Cord

“…One of the best understood mammalian circuits involved in such integration is concerned with reflexes evoked by activation of group II muscle afferents that have powerful and widespread actions on motoneurons (Matthews, 1972;Lundberg et al, 1987b). Recent studies have demonstrated that some group II actions on motoneurons are evoked disynaptically or trisynaptically and hence may be mediated by a pathway including only one or two interneurons (Edgley and Jankowska, 1987a;Lundberg et al, 1987a;Arya et al, 1991;Bajwa et al, 1992). The disynaptic actions of group II afferents have been shown to be evoked via interneurons located ipsilaterally in the intermediate zone and contralaterally in lamina VIII (Cavallari et al, 1987;.…”

Interlimb Coordination During Step-to-Step Transition and Gait Performance

“…The conclusions obtained in each field combined could contribute more significantly to the construction of scientific knowledge about interlimb coordination. In fact, the importance of studying gait interlimb coordination is based on its impact on the metabolic cost of walking (Donelan, et al, 2002a;Donelan, Kram, & Kuo, 2002c;Kuo, Donelan, & Ruina, 2005;Kuo, et al, 2007), and is supported by biomechanical evidence (Donelan, et al, 2002a(Donelan, et al, , 2002cKuo, et al, 2007;Winter & Eng, 1995), and neurophysiological factors at the spinal (Bajwa, Edgley, & Harrison, 1992;Corna, Galante, Grasso, Nardone, & Schieppati, 1996;Dietz, 1992) and supraspinal levels (Drew, Prentice, & Schepens, 2004;Matsuyama et al, 2004).…”