The researchers found that when applied to the prefrontal cortex, tDCS affects a wide portion of the brain, causing changes in functional connectivity between different brain areas that increased learning speed in macaques.
They can now target stimulation, intervening only at critical points, when memory formation is most likely to occur. "We're replicating monkey experiment with stimulation occurring only for one second" he said, "just when it gets the reward." That's when the association is made. They will eventually seek out FDA approval for a particular device. He believes that in 5-10 years, use of this technology will be widespread.
This new understanding of what tDCS does to the brain and its confirmation of tDCS as a learning aid comes in the context of controversy over previous reports that seemed to show no effect on neuron firing rates in cadaver heads, which was generally believed to be the mechanism of interest.