Credit to [montage-explorer](montageexplorer.appspot.com/dosearch?q=electrode:p4(anode)electrode:p4&manualonly=false) for this find. Great tool.

I'm posting this guy up because it illustrates some of the subtleties and limitations to tDCS. In this paper, the researchers claim that High WM users benefited more from tDCS on challenging tasks than Low WM users, irregardless of whether it was the cathode or anode being used on this site. Which is pretty interesting, since in the nootropics/drug world one would expect high-performance due to the Yerkes-Dodson heuristic. So there's a lot to chew on here.

Furthermore the researchers explain the effect observed by stating the following:

We discuss these findings in terms of alternative WM strategies employed by low and high WM capacity individuals. We speculate that low WM capacity individuals do not recruit the posterior parietal lobe for WM tasks as efficiently as high WM capacity individuals. Consequently, tDCS provides greater benefit to individuals with high WM capacity.

This is slightly conformal to what's observed in mathematically gifted children, where if you get these children to do geometric proofs involving "3-D reasoning" or "pre-algebraic thinking", the gifted children recruit a broader network of resources occupying the entire brain (inclusive of the right parietal lobe, but also the ACC and PFC, all bilaterally), over the non-gifted who recruit the right parietal lobe 'only'. (Geake's paper)

I've been looking into the PPC/Right Parietal Cortex as a linchpin to intelligence. Under the P-FIT model, the right parietal cortex serves as a change detection/selective attention master-module and it also seems to be associated with mental imagery. These are my holy grails. It would be good to know or figure out what's stopping the PPC from being activated in low WM users, and find a way to correct that.