transcranial direct current stimulation

[eub]

http://www.nature.com/news/2004/041025/pf/041025-9_pf.html

Connecting a battery across the front of the head can boost verbal skills, says a team from the US National Institutes of Health.

A current of two thousandths of an ampere (a fraction of that needed to power a digital watch) applied for 20 minutes is enough to produce a significant improvement, according to data presented this week at the annual meeting of the Society for Neuroscience, held in San Diego. And apart from an itchy sensation around the scalp electrode, subjects in the trials reported no side-effects.
[...]
The volunteers were asked to name as many words as possible beginning with a particular letter. Given around 90 seconds, most people get around 20 words. But when Iyer administered the current, her volunteers were able to name around 20% more words than controls, who had the electrodes attached but no current delivered. A smaller current of one thousandth of an amp had no effect.

This sounds simpler to implement than transcranial magnetic stimulation. In fact, at work we have several Keithley SMUs that could be set to source 1000 μA, 2000 μA, whatever you like. (YES YES I know several reasons why this is a rotten idea. Even if I turn off the damned broken autoranging mode.)

Transcranial Direct Current Stimulation during Sleep Improves Declarative Memory.

Pharmacological approach to the mechanisms of transcranial DC-stimulation-induced after-effects of human motor cortex excitability.

Excitability changes induced in the human motor cortex by weak transcranial direct current stimulation.

Comments

[eub.livejournal.com]

Batteries are probably your best bet, and a genuine current limiter. I wonder what voltage you need to attain.

[hattifattener]

Yeah, batteries seem like a good way to go. Let's see... sticking my DMM's (uncomfortably pointy) probes into my temples gave me a reading of 5 MΩ, down from 10 MΩ after I wiggled them around a bit. Sticking them both into the same temple gives the same reading (+/- 20%), so presumably that's all skin resistance. Oddly, thumb-to-thumb gives only 500k; what's up with that?

So either you'll need some better skin electrodes than these or your current source is going to need to be able to supply 10,000V to get you that ~2mA. I'd go for the better electrodes, but on the other hand having a Thinking Cap with built-in Van de Graaff generator has a certain style to it.

Random anecdote involving accidental transcranial electrical stimulation: once, as a kid, I was bending over to turn on a faucet, and just as my hand was tightly gripping the steel faucet and the attached pipe — which went directly into the ground and ran underground for a few hundred feet — I leaned over too far and touched my head to the electric fence. It was a decidedly odd experience, but doesn't seem to have caused any harm. No record of whether my Boggle scores went up afterwards.

[eub.livejournal.com]

Thick scalp-skin more resistive than thin thumb-skin, maybe?

Electric fence: ow. Also, I think you mean to say "once, as a kid on the farm".

Hm. 10kV * 2mA = 20 watts? Waaait a minute. Get those probes away from me.