Brain Stimulation - a net positive?

 'The Hidden Costs of Cognitive Enhancement' from Greg Miller, Wired (March 5, 2013), points to some findings that show there are tradeoffs.  There are a number of studies going on using low levels of electrical stimulation to particular areas of the brain while attempting cognitive tasks such as using a new abstract math system.  While there appear to be some findings for faster learning, researchers Cohen Kadosh and his colleague Teresa Iuculano at University of Oxford also looked for follow-on effects.

Those who had the parietal area involved in numerical cognition stimulated learned the new number system more quickly than those who got sham stimulation, the researchers report today in the Journal of Neuroscience. But at the end of the weeklong study their reaction times were slower when they had to put their newfound knowledge to use to solve a new task that they hadn’t seen during the training sessions. ”They had trouble accessing what they’d learned,” Cohen Kadosh said.

See also this story 'Electrical Brain Stimulation Helps People Learn Math Faster' - also by Miller - May 16, 2013.