Very well researched and well-balanced article from Mark Harris at The Economist.
Hardly surprising, then, that DIY brain hackers want in on the action. Christopher Zobrist, a 36-year-old entrepreneur based in Vietnam, is one of them. With little vision he has been registered as blind since birth due to an hereditary condition of his optic nerve that has no established medical treatment. Mr Zobrist read a study of a different kind of transcranial stimulation (using alternating current) that had helped some glaucoma patients in Germany recover part of their vision. Despite neither the condition nor the treatment matching his own situation, Mr Zobrist decided to try tDCS in combination with a visual training app on his tablet computer. He quickly noticed improvements in his distance vision and perception of contrast. “After six months, I can see oncoming traffic two to three times farther away than before, which is very helpful when crossing busy streets,” he says.
Equally troublesome is a meta-analysis of the cognitive and behavioural effects on healthy adults that Mr Horvath subsequently carried out. As before, he included only the most reliable studies: those with a sham control group and replicated by other researchers. It left 200 studies claiming to have discovered beneficial effects on over 100 activities such as problem solving, learning, mental arithmetic, working memory and motor tasks. After his meta-analysis, however, tDCS was found to have had no significant effect on any of them.
If tDCS alters neither the physiology of the brain nor how it performs, thinks Mr Horvath, then evidence suggests it is not doing anything at all. Marom Bikson, a professor of biomedical engineering at City University of New York, disagrees. “I can literally make you fall on your butt using the ‘wrong’ type of tDCS,” he says. Dr Bikson thinks the biggest challenge for tDCS is optimising techniques, such as the dose.
Roi Cohen Kadosh is a leading non-invasive brain stimulation researcher. (Also elsewhere on the blog)
A new line of research opens the possibility of modulating and enhancing human cognition using mild and painless transcranial electrical stimulation (tES), which includes transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS) and transcranial random noise stimulation (tRNS). Such initial findings trigger excitement as well as scepticism. The current review aims to provide a guideline for those who are interested in expanding their research into this field. I will therefore discuss: (1) the principles of tES and its putative mechanisms; (2) its potential to modulate and enhance cognitive abilities; (3) the misconceptions on which scepticism about this method is based; and (4) possible directions for the advancement of this field in which psychologists in general and cognitive psychologists in particular should in my view play a key role. I will conclude that this nascent field, which has been neglected by psychologists, requires their contribution in order to lead to basic and translational advancements on human behaviour.
And another excerpt around the hot topic of ‘transfer’… Basically, that it’s difficult to measure (positive effects of stimulation leading to enhanced intelligence) when we’re not even sure what cognition means.
Another closely related issue in cognitive enhancement and training is the issue of transfer (Taatgen, 2013). Currently, there is mixed evidence from tES-paired training studies of transfer of tES-training benefits to another task. One of the issues regarding this lack of consistency is the difficulty of selecting appropriate training and transfer tasks, and this in my view is often due to a difficulty in identifying which cognitive functions and brain regions are activated by the specific training material. In other words, the constraint might not be due to the limited potential of tES to induce transfer, but due to suboptimal experimental design. This drawback is not limited to tES, but is a generic problem in the field of rehabilitation and cognitive enhancement (Cohen Kadosh, 2014). Indeed, some studies have shown that tES can even further increase the chance of transfer in paradigms that have struggled to show transfer without stimulation (Cappelletti et al., 2013; Looi, Duta, Huber, Nuerk, & Cohen Kadosh, 2013). Further studies are needed to examine the multifaceted issue of transfer effects, and their possible enhancement using tES. However, in order for such knowledge to progress, a better understanding of the cognitive mechanisms involved is necessary (Taatgen, 2013).