title: Persistence of locomotor-related interlimb reflex networks during walking after stroke.
abstract: OBJECTIVE
  Cutaneous nerve stimulation evokes coordinated and phase-modulated reflex output widely distributed to muscles of all four limbs during walking. Accessibility to this distributed network after stroke offers insight into the pathological changes and suggests utility for therapeutic applications. Here we examined muscles in both the more (MA) and less affected (LA) legs evoked by stimulation at the ankle and wrist during walking in chronic (>6 months post CVA) stroke.
  
  
  METHODS
  Stroke and control participants walked on a treadmill with a harness support system. Reflexes were evoked with trains of electrical stimuli delivered separately to the cutaneous superficial peroneal (SP; at the ankle) and superficial radial (SR; at the wrist) nerves. Background locomotor and reflex EMG were phase-averaged across the gait cycle and analyzed off line.
  
  
  RESULTS
  Locomotor background muscle activation patterns were altered bilaterally in stroke, as compared with control. Phase-dependent modulation of interlimb cutaneous reflexes was found in both stroke and control subjects with stimulation of each nerve, but responses were blunted in stroke. Reflex reversal in tibialis anterior (TA) at heel strike with SP nerve stimulation was present in both groups. Notably, SR nerve stimulation produced facilitation during the swing-to-stance transition in the TA and suppression of MG in the MA leg during stance.
  
  
  CONCLUSIONS
  Interlimb cutaneous inputs may access coordinated reflex pathways in the MA limb during walking after stroke. Importantly activation in these pathways could provoke responses to counter foot drop during swing phase of walking. Additionally, our data support the perspective that there is no "unaffected" side after stroke and that caution should be used when interpreting the LA side as "control" after stroke.
  
  
  CONCLUSIONS
  The presence of functionally-relevant interlimb cutaneous reflexes in the MA leg presents a substrate that may be strengthened by rehabilitation.
authors.affiliation: Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, BC, Canada. pzehr@uvic.ca
authors.forename: E Paul
authors.initials: EP
authors.lastname: Zehr
authors.forename: Pamela M
authors.initials: PM
authors.lastname: Loadman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000842:Ankle / Q000502:physiology; D001696:Biomechanical Phenomena; D003627:Data Interpretation, Statistical; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D005528:Foot / Q000502:physiology; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007866:Leg / Q000502:physiology; D008124:Locomotion / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000503:physiopathology*; D012018:Reflex / Q000502:physiology*; D020521:Stroke / Q000503:physiopathology*; D016138:Walking / Q000502:physiology*; D014953:Wrist / Q000502:physiology