Transcranial Electrical Stimulation (tES)

 

The oldest and yet the most commonly used method of brain stimulation is transcranial electrical stimulation (tES). A technique of electrical stimulation that has recently attracted great attention among researchers is transcranial direct current stimulation (tDCS). Like other methods of brain stimulation, the interesting feature of this technique for researchers is the ability to examine the relationship between brain and behavior. tDCS allows you to increase or decrease the activity of any area of the brain. This tool is also utilized to better understand the neural correlates of cognitive functions such as memory, attention, and decision-making.

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A tDCS device consists of a main part and a few electrodes. A 9-V battery is the main power supply of the device that conducts the direct current (DC) of 0.5 to 4 mA over the target area of the brain. Transcranial alternating current stimulation (tACS) is another method that has recently received great attention and been applied by neuroscientists and psychologists to better analyze the cerebral functions. tACS has been proven to be an appropriate tool to increase a specific frequency band, e.g. alpha, in the brain. Considering our relative knowledge of electrophysiological correlates of cognitive and behavioral functions, tACS helps study and affect these cerebral structures.  

The review of the literature on tACS can show how much this technique has developed over the past years. Based on a search on PubMed, 1,500 papers on tACS have been published from 2011 to 2015. This figure is comparable with the 65 papers on this field published from 2000 to 2005. A recent review study on papers about tACS published from 1998 to 2016 revealed that a total of 2,457 papers on tACS were published during the last 18 years, according to Web of Science. The table below demonstrates the growth rate of papers published in this field.

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According to this table, there has been a significant increase in the number of papers published in this field. Japanese researchers have published the highest number of papers on tACS in Asia. Among developing countries, Iran, Brazil, South Korea, India, Thailand, and Turkey have published the highest numbers of papers on tDCS. This shows that Iranian researchers are fully aware of the benefits of this tool and commonly employ it in their studies in the field of neuroscience.

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Like TMS, tDCS can also be combined with neuroimaging methods such as EED and fMRI. Therefore, it will be possible for us to monitor the online physiological changes caused by each of these methods.

 

Brain Stimulation Facilities at Atieh

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This laboratory is equipped with an advanced electrical stimulator (NeuroConn DC-Stimulator Plus). Consisting of a stimulation channel. This device has the following features:

-          tDCS

-          tACS

-          Four types of standard stimulation: tDCS (continuous stimulation), pulse (activation/deactivation of circular stimulation), sinus (sinus wave), noise (normal noise)

-          Phase and frequency adjustability

-          tES with round electrodes

This device is also able to simultaneously record EEG with AC and DC stimulation.