Working memory, as associated with ‘brain training’ and ‘plasticity‘, is often expressed as what one would wish to have more of, or at the very least, what one hopes not to lose as we age. (For a great overview of working memory and the how’s of enhancing it, see this fascinating post from neuroscientist Bradley Voytek’s blog Working memory and cognitive enhancement.)
Our aim was to determine whether anodal transcranial direct current stimulation, which enhances brain cortical excitability and activity, would modify performance in a sequential-letter working memory task when administered to the dorsolateral prefrontal cortex DLPFC. Fifteen subjects underwent a three-back working memory task based on letters. This task was performed during sham and anodal stimulation applied over the left DLPFC. Moreover seven of these subjects performed the same task, but with inverse polarity cathodal stimulation of the left DLPFC and anodal stimulation of the primary motor cortex M1. Our results indicate that only anodal stimulation of the left prefrontal cortex, but not cathodal stimulation of left DLPFC or anodal stimulation of M1, increases the accuracy of the task performance when compared to sham stimulation of the same area. This accuracy enhancement during active stimulation cannot be accounted for by slowed responses, as response times were not changed by stimulation. Our results indicate that left prefrontal anodal stimulation leads to an enhancement of working memory performance. Furthermore, this effect depends on the stimulation polarity and is specific to the site of stimulation. This result may be helpful to develop future interventions aiming at clinical benefits.
Transcranial Direct Current Stimulation Procedures
TDCS was applied using an ActivaDose II Iontophoresis Delivery Unit, which provides for delivery of a constant low level of direct current. Square-shaped (11 cm2) saline-soaked (0.9% sodium saline solution) sponge electrodes were attached to the participant with self-adhesive bandage strips. The anode was placed near electrode site F10 in the 10-10 EEG system, over the right sphenoid bone. The cathode was placed on the contralateral (left) upper arm. The site of the anode was selected based on our previous fMRI results showing that this brain region was the primary locus of neural activity associated with performance this task .
Anodal 2 mA current was applied to the scalp electrode site F10 in the 10-10 EEG system. The resulting enhancement of performance in the threat detection task is consistent with our previous fMRI results  showing that the right inferior frontal cortex is a major locus of a distributed brain network that mediates performance on this task. The right parietal cortex is a part of this network and could also be a target for stimulation.
One possible explanation for the improvement in detection performance (hit rate) in the threat detection task is that tDCS increases general arousal, thereby leading to a change in response bias in the more liberal direction , which would increase the hit rate. However, computation of signal detection metrics showed that there were no significant effects of tDCS on the ß measure of response bias. Instead, the effect of brain stimulation was to enhance perceptual sensitivity, d′.
The improvement in perceptual sensitivity suggests that participants receiving tDCS were better able to encode stimulus features that distinguished targets and non-targets, which in turn led to accelerated learning and improved retention.
We had a look at the Valkee earlier on the blog. I just bring it up again because it’s interesting that TechCrunch is covering it and pointing out its ‘successful startup’ aspect. I can’t imagine a DIY version of this could cost more than a few dollars.
“I told him you don’t need to your light your house. You need to light your brain,” Nissila said. The ear canal was the most natural and obvious way to shine light onto the surface of the brain. Within weeks, they had a prototype.
Called The Valkee, the device looks like an MP3 player with a set of fancy headphones attached to it. The earbuds actually have a pair of lights attached to them that run for 12-minute sessions at a time. The idea is that by shining light into sensitive areas of the brain, it will stimulate a special OPN3 protein in parts of the brain that help regulate serotonin, melatonin and dopamine production.
They’re initially marketing it to people with Seasonal Affective Disorder, but they’re planning to expand their consumer base to people who need to fight off jet lag.
“If I stop using it for one week, I start eating more and it becomes very difficult to wake up in the morning,” said Timo Ahopelto, who was CEO of the company before leaving to join early-stage Finnish VC fund Lifeline Ventures, which also holds a stake in Valkee. I’ve used it, and I can’t tell if there is any effect yet beyond making my ears feel warm in the morning. But I’m also Californian, so I’m not even really sure I suffer from seasonal affective disorder because we don’t really have seasons.