title: Transcranial direct current stimulation of the premotor cortex: effects on hand dexterity.
abstract: Premotor cortex activity is associated with complex motor performance and motor learning and offers a potential target to improve dexterity by transcranial direct current stimulation (tDCS). We explored the effects of tDCS of premotor cortex on performance of a Strength-Dexterity test in healthy subjects.
  
  
  METHODS
  During the test a slender spring held between thumb and index finger should be compressed as much as possible without buckling. Finger forces assessed in the test provided a measure of dexterity. First, task performance was tested in 12 persons during anodal tDCS to the primary motor cortex (M1) contralateral to the performing hand, and sham stimulation. Another 12 persons participated in five sessions of anodal and cathodal tDCS over the left and the right premotor cortex and sham stimulation.
  
  
  RESULTS
  tDCS over M1 as well as over the left, but not the right premotor cortex resulted in significant improvement of performance. Performance alterations correlated positively between left anodal and right cathodal tDCS and negatively between anodal tDCS of the two sides. Effective polarity for premotor stimulation to improve task performance differed between participants. Individuals who improved with anodal stimulation used lower finger force and experienced the test as more difficult compared to those who improved with cathodal stimulation.
  
  
  CONCLUSIONS
  This study demonstrates that tDCS over the left premotor cortex can improve performance of a dexterity demanding task. The effective polarity of stimulation depends on the task performance strategies. The study moreover shows a functional relevance of interactions between the left and right premotor cortex.
authors: Department of Clinical Sciences, Rehabilitation medicine, Karolinska Institute, Danderyd Hospital, entrée 39, floor 3, 18288 Stockholm, Sweden. Electronic address: elena.pavlova@ki.se.
authors: Elena
authors: E
authors: Pavlova
authors: Department of Clinical Neurophysiology, Georg-August-Universität Göttingen, Robert-Koch-Strasse 40, 37075 Göttingen, Germany. Electronic address: i5484133@gmail.com.
authors: Min-Fang
authors: MF
authors: Kuo
authors: Department of Clinical Neurophysiology, Georg-August-Universität Göttingen, Robert-Koch-Strasse 40, 37075 Göttingen, Germany. Electronic address: mnitsch1@gwdg.de.
authors: Michael A
authors: MA
authors: Nitsche
authors: Department of Clinical Sciences, Rehabilitation medicine, Karolinska Institute, Danderyd Hospital, entrée 39, floor 3, 18288 Stockholm, Sweden. Electronic address: jorgen.borg@ki.se.
authors: Jörgen
authors: J
authors: Borg
mesh_terms: D000328:Adult; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D005385:Fingers / Q000502:physiology; D007839:Functional Laterality; D006225:Hand / Q000502:physiology*; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D012016:Reference Values; D065908:Transcranial Direct Current Stimulation; D055815:Young Adult
keywords: Dexterity; Dorsal premotor cortex; PMd; Strength–Dexterity test; Transcranial direct current stimulation; tDCS