What is neurostimulation?

Neurostimulation is a term used to describe a variety of invasive and non-invasive techniques which utilise electrical signals to affect long-lasting alterations to neuronal activity or excitability.

Transcranial Electrical Stimulaton (tES):

tES is an umbrella term used to describe a variety of non-invasive neurostimulation techniques. Some are outlined briefly below:

  • tDCS (transcranial Direct Current Stimulation) – typically involves two saline-soaked electrodes being placed on the scalp and then a weak and painless continuous current (normally no higher than 2mA) is applied for anywhere between 2 and 20 minutes. tDCS can assist patients with brain injuries as well as those with depression.
  • tMS – (Transcranial magnetic stimulation) – typically involves placing a coil which generates magnetic fields on the head to stimulate a small area of the brain (frontal region). It is usually applied or around 20 to 30 minutes. The purpose of tMS is to alleviate symptoms of depression in patients who cannot tolerate or do not respond to medication.
  • tACS – transcranial alternating current stimulation – typically involves the placement of a large electrode on an area of interest in the brain, whilst another reference electrode is placed in a neutral location. Unlike tDCS, tACS oscillates a sinusoidal current at a selected frequency so that it interacts with the brain’s natural oscillations. tACS is currently being explored for use in Parkinson’s disease, schizophrenia, cognitive enhancement and more.

The benefits of non-invasive neurostimulation

Aside from alleviating symptoms of depression and schizophrenia, numerous studies have reported the benefits of neurostimulation upon cognitive ability, learning and performance. In recent years, DIY neurostimulation has become increasingly popular among individuals who wish to improve their cognitive function for everyday purposes such as work and education.

Emerging research on tES

Some exciting applications for tES have emerged through recent research projects. Some are listed below:

A randomised controlled study (2017) explored the effects of transcranial direct current stimulation (tDCS) on 22 medical students receiving simulation training in the neurosurgical removal of tumours. Results showed that those who received the tDCS compared to those who did not had enhanced motor skills, which translated into greater effectiveness and efficiency in removing tumours and a reduction in the application of excessive force. Results also showed little or no reduction in these skills after a 6 week follow up. Further research could explore whether similar results can be achieved with non-simulated surgical skills or other motor skills entirely.

A 2018 study investigated the effects of tDCS on neuromuscular function and performance during a cycling test. Twelve participants received either placebo tDCS or real tDCS, with one cathode applied to the motor cortices and one to the ipsilateral shoulders. Sessions lasted for 10 minutes with a current set at 2mA. Neuromuscular assessment was performed before and after the application of tDCS and was followed by a cycling ‘time to task failure’ (TTF) test. Heart rate, perceived exertion, leg muscle pain and blood lactate accumulation were all measured. Results showed that those who received the real tDCS demonstrated improved endurance performance compared to those assigned to the placebo tDCS.

References:

Ciechanski, P., Cheng, A., Lopushinsky, S., Hecker, K., Shi Gan, L., Lang, S.,…Kirton, A. (2017). Effects of transcranial direct-current stimulation on neurosurgical skill acquisition: A randomised controlled trial. World Neurosurgery, 108. 876-884. doi: 10.1016/j.wneu.2017.08.123

Angius, L., Mauger, A., Hopker, J., Pascual-Leone, A., Santarnecchi, & Marcora, S. (2018). Bilateral extracephalic transcranial direct current stimulation improves endurance performance in healthy individuals. Brain Stimulation, 11. 108-117. Doi: 10.1016/j.brs.2017.09.017

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