title: A Comparison of Primed Low-frequency Repetitive Transcranial Magnetic Stimulation Treatments in Chronic Stroke.
abstract: BACKGROUND
  Preceding low-frequency repetitive transcranial magnetic stimulation (rTMS) with a bout of high-frequency rTMS called priming potentiates the after-effects of the former in healthy adults. The utility of primed rTMS in stroke remains under-explored despite its theoretical benefits in enhancing cortical excitability and motor function.
  
  
  OBJECTIVE
  To ascertain the efficacy of priming in chronic stroke by comparing changes in cortical excitability and paretic hand function following three types of primed low-frequency rTMS treatments.
  
  
  METHODS
  Eleven individuals with chronic stroke participated in this repeated-measures study receiving three treatments to the contralesional primary motor cortex in randomized order: 6 Hz primed 1 Hz rTMS, 1 Hz primed 1 Hz rTMS, and sham 6 Hz primed active 1 Hz rTMS. Within- and between-treatment differences from baseline in cortical excitability and paretic hand function from baseline were analyzed using mixed effects linear models.
  
  
  RESULTS
  6 Hz primed 1 Hz rTMS produced significant within-treatment differences from baseline in ipsilesional cortical silent period (CSP) duration and short-interval intracortical inhibition. Compared to 1 Hz priming and sham 6 Hz priming of 1 Hz rTMS, active 6 Hz priming generated significantly greater decreases in ipsilesional CSP duration. These heightened effects were not observed for intracortical facilitation or interhemispheric inhibition excitability measures.
  
  
  CONCLUSIONS
  Our findings demonstrate the efficacy of 6 Hz primed 1 Hz rTMS in probing homeostatic plasticity mechanisms in the stroke brain as best demonstrated by differences CSP duration and SICI from baseline. Though 6 Hz priming did not universally enhance cortical excitability across measures, our findings pose important implications in non-invasive brain stimulation application in stroke rehabilitation.
authors.affiliation: Program in Rehabilitation Science, University of Minnesota, USA; Program in Physical Therapy, Department of Physical Medicine and Rehabilitation, University of Minnesota, USA. Electronic address: jmkream@gmail.com.
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Cassidy
authors.affiliation: Division of Biostatistics, School of Public Health, University of Minnesota, USA.
authors.forename: Haitao
authors.initials: H
authors.lastname: Chu
authors.affiliation: Department of Neurology, University of Minnesota Medical School, USA.
authors.forename: David C
authors.initials: DC
authors.lastname: Anderson
authors.affiliation: Courage Kenny Rehabilitation Institute, Minneapolis, MN, USA.
authors.forename: Linda E
authors.initials: LE
authors.lastname: Krach
authors.affiliation: Program in Physical Therapy, Department of Physical Medicine and Rehabilitation, University of Minnesota, USA.
authors.forename: LeAnn
authors.initials: L
authors.lastname: Snow
authors.affiliation: Program in Physical Therapy, Department of Physical Medicine and Rehabilitation, University of Minnesota, USA.
authors.forename: Teresa J
authors.initials: TJ
authors.lastname: Kimberley
authors.affiliation: Program in Physical Therapy, Department of Physical Medicine and Rehabilitation, University of Minnesota, USA.
authors.forename: James R
authors.initials: JR
authors.lastname: Carey
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease; D018592:Cross-Over Studies; D004311:Double-Blind Method; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology; D020521:Stroke / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D016896:Treatment Outcome
keywords: Homeostatic plasticity; Metaplasticity; Priming; Repetitive transcranial magnetic stimulation; Stroke