Polarization of the human motor cortex through the scalp

Alberto Priori, Alfredo Berardelli, Sabine Rona, Neri Accornero, Mario Manfredi

Research output: Contribution to journalArticlepeer-review


Direct currents (DC) applied directly to central nervous system structures produce substantial and long-lasting effects in animal experiments. We tested the functional effects of very weak scalp DC (<0.5 mA, 7 s) on the human motor cortex by assessing the changes in motor potentials evoked by transcranial magnetic brain stimulation. We performed four different experiments in 15 healthy volunteers. Our findings led to the conclusion that such weak (<0.5 mA) anodal scalp DC, alternated with a cathodal DC, significantly depresses the excitability of the human motor cortex, providing evidence that a small electric field crosses the skull and influences the brain. A possible mechanism of action of scalp DC is the hyperpolarization of the superficial excitatory interneurones in the human motor cortex.

Original languageEnglish
Pages (from-to)2257-2260
Number of pages4
Issue number10
Publication statusPublished - Jul 13 1998


  • Cortical interneurones
  • Corticomotoneuronal connection
  • Descending volley
  • Direct current
  • Motor cortex
  • Motor potentials
  • Polarization
  • Transcranial magnetic brain stimulation

ASJC Scopus subject areas

  • Neuroscience(all)


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