Here is an intriguing finding, from a team I last saw in a very agreeable restaurant in Graz. They have found a way of boosting performance on difficult items of a matrix problem task, by using in-task transcranial stimulation. They are tentative, but speculate that the externally imposed effect might mimic some cortical control process, which could be very productive.
THE INFLUENCE OF TRANSCRANIAL ALTERNATING CURRENT STIMULATION (TACS) ON FLUID INTELLIGENCE PERFORMANCE. AN FMRI STUDY
Aljoscha C. Neubauer1 , Martin Wammerl1 , Mathias Benedek1 , Emanuel Jauk1 , Norbert Jausovec2
1 University of Graz, firstname.lastname@example.org.
2 University of Maribor.
Recently, the issue was raised whether fuid intelligence can be increased through (mostly working memory) training. Despite some initial supportive evidence (Jaeggi, et al., 2008) more recent studies did not find support for training effects (e.g. Colom et al., 2013; Owen et al., 2010). Moreover, the method is critically discussed for methodical problems (Shipstead, et al., 2012). It seems questionable whether intelligence can be enhanced through cognitive training in a consistent and long-lasting manner (Haier, 2014).
We tested whether fluid intelligence (gf) could be enhanced by directly influencing brain activity through transcranial alternating current stimulation (tACS) applied to the parietal cortex and at the same time measuring concomitant changes in brain activity by fMRI. In a double-blind, sham-controlled experiment 20 participants performed two fluid intelligence tasks (matrices task, and paper folding & cutting, PFC) after either transcranial alternating current stimulation (tACS) at theta frequency or sham stimulation was applied.
The stimulation site was the lef parietal cortex (P3), because of its key role for intelligence and intelligence-related functions (e.g., working memory capacity, verbal memory, spatial working memory). Sham and verum conditions were realized within-participants (using parallel test versions of both tests) with the two sessions separated by 28 days. While working on the two tasks stimulation-induced brain activity changes were recorded using fMRI.
Results indicated task- and difficulty-specific stimulation effects: When solving difficult items of matrices test verum tACS significantly increased gf performance, as compared to sham. No difference emerged for easy items.
In the second gf task (PFC), tACS had no effect. For Raven matrices test whole-brain analyses showed that left parietal brain stimulation was accompanied by less right sided activation in areas of the frontal lobe, fusiform gyrus and occipital lobe, as well as left sided middle occipital gyrus. Additional ROI analyses revealed a tendency for less activation in the left inferior parietal lobule.
We conclude that left parietal theta tACS could enhance performance in a reasoning task but only for difficult items; and not for a gf task requiring mental rotation. We presume that theta frequency resembles a general cognitive control process, which might be of importance for gf performance. Neurophysiologically, the tACS-induced reductions of brain activation primarily concerned brain areas that partly overlapped with the task-negative network (e.g., precuneus). This seems in line with the neural efficiency hypothesis, that higher gf is related to lower activation, mainly in task-negative brain regions (Basten et al., 2013; Dunst et al., 2014; Neubauer & Fink, 2009).
But so far, the current findings can only be interpreted as transient increases in gf test performance rather than in gf per se. Though the enhancement could be intelligence-specific, also other processes might account for tACS induced increases in gf performance (cf. Haier, 2014).