title: Transcranial direct current stimulation effects on I-wave activity in humans.
abstract: Transcranial direct current stimulation (tDCS) of the human cerebral cortex modulates cortical excitability noninvasively in a polarity-specific manner: anodal tDCS leads to lasting facilitation and cathodal tDCS to inhibition of motor cortex excitability. To further elucidate the underlying physiological mechanisms, we recorded corticospinal volleys evoked by single-pulse transcranial magnetic stimulation of the primary motor cortex before and after a 5-min period of anodal or cathodal tDCS in eight conscious patients who had electrodes implanted in the cervical epidural space for the control of pain. The effects of anodal tDCS were evaluated in six subjects and the effects of cathodal tDCS in five subjects. Three subjects were studied with both polarities. Anodal tDCS increased the excitability of cortical circuits generating I waves in the corticospinal system, including the earliest wave (I1 wave), whereas cathodal tDCS suppressed later I waves. The motor evoked potential (MEP) amplitude changes immediately following tDCS periods were in agreement with the effects produced on intracortical circuitry. The results deliver additional evidence that tDCS changes the excitability of cortical neurons.
authors: Department of Neurology, Christian-Albrechts University, Kiel, Germany.
authors: Nicolas
authors: N
authors: Lang
authors: Michael A
authors: MA
authors: Nitsche
authors: Michele
authors: M
authors: Dileone
authors: Paolo
authors: P
authors: Mazzone
authors: Javier
authors: J
authors: De Andrés-Arés
authors: Luis
authors: L
authors: Diaz-Jara
authors: Walter
authors: W
authors: Paulus
authors: Vincenzo
authors: V
authors: Di Lazzaro
authors: Antonio
authors: A
authors: Oliviero
mesh_terms: D000328:Adult; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation