Since tDCS is noninvasive technique of stimulation and has mainly modulating effects on brain tissue, the direct measurement is not possible. Is anyone aware of some simulation or biophysics study (beside Miranda) which determined the amount of electricity ( I read about the approximately 1 micro Coulomb) which is moved by this application. Thank you!
Actually, there have been recent studies where researchers have made direct measurements of the electric field (volts/meter) during tDCS. These works utilize electrode arrays implanted in patients with epilepsy to measure the electric field from tDCS.
From Huang et al: https://elifesciences.org/articles/18834
From Opitz et al: Article On the importance of precise electrode placement for targete...
In the Huang paper, they say the electric field approaches 0.8V/m at 2mA. It is important to remember that this will vary a decent amount between individuals (see Article Inter-subject Variability in Electric Fields of Motor Cortical tDCS
), and will also depend on the size/positioning of electrodes.If you just want the total number of coulombs delivered by the device, you can take 0.002 Amps * duration of stimulation (in seconds). But coulombs isn't a very useful unit of measurement for tDCS and this just tells you the number of coulombs passing through the electrodes, not the brain.
Eric, thank you very much. I am interested in elucidating in actual impact of stimulation on the brain and the difference in the state if the brain before and after the stimulation.
Thanks!
In addition of some research according to the head model and evaluate the effect of tDCS current in simulation, if you interest to see the effect of tDCS, you can design a protocol and record data before and after stimulation. Thus, by considering these data and extracting some relevant features you may see the effect of tDCS. To be more specific, you can evaluate this effect by statistical analysis. I've done some researches in this area.
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