title: Influence of somatosensory input on interhemispheric interactions in patients with chronic stroke.
abstract: BACKGROUND
  Ischemia-induced cutaneous anesthesia of the healthy hand in patients with chronic stroke elicits transient improvements of motor performance in the contralateral, paretic hand.
  
  
  OBJECTIVE
  The present study was designed to investigate one of the possible mechanisms underlying this effect.
  
  
  METHODS
  The authors evaluated the effects of transient ischemic cutaneous anesthesia of the healthy hand (target intervention) and healthy foot (control intervention) on transcranial magnetic stimulation-induced interhemispheric inhibition from the contralesional onto the ipsilesional primary motor cortex (M1). Ten subjects with chronic, predominantly subcortical stroke with motor impairment were assessed.
  
  
  RESULTS
  Cutaneous anesthesia of the intact hand but not the intact leg resulted in reduction of the inhibitory drive from the contralesional to the ipsilesional M1 both at rest and immediately preceding movements of the paretic hand. Changes in premovement interhemispheric inhibition showed a trend for correlation with improvements in finger-tapping speed in the paretic hand.
  
  
  CONCLUSIONS
  The findings suggest that modulation of interhemispheric inhibitory interactions between the contralesional and ipsilesional M1, either primarily or secondary to intrahemispheric excitability changes in either hemisphere, may contribute to performance improvements with cutaneous anesthesia of the intact hand. The present study provides additional insight into the mechanisms by which rehabilitative interventions focused on training one hand and restraining the other may operate after chronic stroke.
authors.affiliation: Human Cortical Physiology Section and Stroke Neuro-rehabilitation Clinic, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20817-1428, USA.
authors.forename: Agnes
authors.initials: A
authors.lastname: Floel
authors.forename: Friedhelm
authors.initials: F
authors.lastname: Hummel
authors.forename: Julie
authors.initials: J
authors.lastname: Duque
authors.forename: Stefan
authors.initials: S
authors.lastname: Knecht
authors.forename: Leonardo G
authors.initials: LG
authors.lastname: Cohen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000772:Anesthesia, Local; D005260:Female; D006225:Hand; D006801:Humans; D008297:Male; D008875:Middle Aged; D009048:Motor Skills; D009433:Neural Inhibition / Q000502:physiology; D010291:Paresis / Q000209:etiology / Q000503:physiopathology / Q000534:rehabilitation*; D011930:Reaction Time; D020127:Recovery of Function; D013003:Somatosensory Cortex / Q000503:physiopathology*; D020886:Somatosensory Disorders / Q000209:etiology / Q000503:physiopathology / Q000534:rehabilitation*; D020521:Stroke / Q000503:physiopathology*; D000071939:Stroke Rehabilitation; D016896:Treatment Outcome