Magstim DC Stimulation

Transcranial direct current stimulation (tDCS) involves applying weak electrical currents to the head, to generate an electromagnetic field which modulates the activity of brain neurons. tDCS is known to selectively modulate neuronal excitability and can be used in conjunction with fMRI, transcranial magnetic stimulation (TMS) or centrally acting drugs. It is being investigated as a treatment for a variety of conditions such as stroke recovery, depression and migraine.Magstim tDCS Stimulator and Electodes

Extensive neurophysiological experiments have shown evidence that Direct Current (DC) penetrates the brain to modify neuronal transmembrane potentials, thereby influencing the level of excitability and modulating firing rates1.

Studies suggest, that if cathodal stimulation – negative pole or electrode (cathode) is located near the cell body or dendrites – it decreases the resting membrane potential and therefore hyperpolarises neurones, whereas if anodal stimulation – positive pole or electrode (anode) is located near the cell body or dendrites – it causes depolarisation by increasing resting membrane potentials and spontaneous neuronal discharge rates2.

Current research suggests that electrodes placed on the forehead can produce noticeable psychological changes that are dependent on the direction of the field.

Lang et al3 claim that anodal polarisation of the motor cortex increased the motor response to TMS of the same area; reduction of this response was observed with cathodal polarisation, the effects of which seem to last for an appreciable amount of time after exposure. Investigators are currently testing the validity of these claims and the effects of tDCS on other brain areas and functions.

tDCS is now emerging as a major research tool in its own right and as a complimentary tool to conventional TMS.

  • In studies of the visual system Antal et al4 working with Professor Walter Paulus in Göttingen, have used tDCS to modulate visual cortex excitability measured using TMS, and to enhance visuomotor learning.
  • In cognitive studies tDCS has been used to change probabilistic learning in adults and to study working memory. These studies have stimulated V1, V5/MT, parietal cortex and prefrontal cortex5.
  • Studies applying tDCS to the motor cortex have revealed that tDCS can modulate motor cortex excitability (measured using TMS) for up to 90 minutes post stimulation6. Exploiting this long term change in brain sensitivity has allowed exploration of motor learning and plasticity.
  • The long term effects of tDCS make it an effective tool to use in conjunction with centrally acting drugs and one study has shown that dopaminergic modulation combined with tDCS can enhance the effects of tDCS for up to 24 hours7.
  • The rehabilitation potential of tDCS remains to be explored but already, in rehabilitation following stroke, tDCS has been combined with measures of plasticity in double blind trials to give promising indications of a positive role for non invasive DC stimulation in rehabilitation8.

Magstim eldith DC Stimulators are excellent devices for research in this exciting and developing field, being both portable and durable, with clear displays and easy to use controls. The variety of settings gives researchers the scope that they need to conduct their studies.

CAUTION: Investigational Device. Federal or (United States) law limits device to investigational use.

References

1  Technology Insight: non-invasive brain stimulation in neurology – perspectives on the therapeutic potential of rTMS and tDCS.
Nature Clinical Practice Neurology 383: July 2007 Vol. 3 No. 7
Fregni F, Pascual-Leone A.

2  Safety aspects of transcranial direct current stimulation concerning healthy subjects and patients.
Brain Research Bulletin 72 (2007) 208–214
Csaba Poreisz, Kl´ara Boros, Andrea Antal, Walter Paulus

3  Preconditioning with transcranial direct current stimulation sensitizes the motor cortex to rapid-rate transcranial magnetic stimulation and controls the direction of after-effects
Biological Psychiatry, Volume 56, Issue 9, 1 November 2004, Pages 634-639
Nicolas Lang, Hartwig R. Siebner, Diana Ernst, Michael A. Nitsche, Walter Paulus, Roger N. Lemon and John C. Rothwell

4  Transcranial direct current stimulation and the visual cortex
Brain Research Bulletin, Volume 68, Issue 6, 15 February 2006, Pages 459-463
Andrea Antal, Michael A. Nitsche and Walter Paulus

5  Facilitation of probabilistic classification learning by transcranial direct current stimulation of the prefrontal cortex in the human
Neuropsychologia, Volume 42, Issue 1, 2004, Pages 113-117
Tamás Z. Kincses, Andrea Antal, Michael A. Nitsche, Orsolya Bártfai and Walter Paulus

6  Has transcranial alternating current stimulation had consistent effects on cortical excitability in humans?
Brain Stimulation, In Press, Uncorrected Proof, and Available online 3 December 2007
Andrea Antal, Klára Boros, Csaba Poreisz, Leila Chaieb, Daniella Terney and Walter Paulus

7  Dopaminergic modulation of long-lasting direct current-induced cortical excitability changes in the human motor cortex.
European Journal of Neuroscience, Volume 23 Issue 6 Page 1651-1657, March 2006
Michael A. Nitsche, Christian Lampe, Andrea Antal, David Liebetanz, Nicolas Lang, Frithjof Tergau and Walter Paulus

8  Transcranial direct current stimulation of the unaffected hemisphere in stroke patients.
Neuroreport. 16(14):1551-1555, September 28, 2005.
Fregni, Felipe; Boggio, Paulo S.; Mansur, Carlos G.; Wagner, Tim; Ferreira, Merari J. L.; Lima, Moises C.; Rigonatti, Sergio P.; Marcolin, Marco A.; Freedman, Steven D.; Nitsche, Michael A.; Pascual-Leone, Alvaro

For a more complete literature review of recently published papers relating to tDCS please click here.

For regulatory issues information in the USA please click here.

For futher information, queries or feedback, please contact magstim.info@magstim.com

Magstim DC Stimulation: Magstim_tDCS_Brochure.pdf (3204k)