In summary — “I am cautiously optimistic about the promise of tDCS; cognitive training paired with tDCS specifically could lead to improvements in attention and memory for people of all ages and make some huge changes in society. Maybe we could help to stave off cognitive decline in older adults or enhance cognitive skills, such as focus, in people such as airline pilots or soldiers, who need it the most. Still, I am happy to report that we have at least moved on from torpedo fish” smile

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In 47 CE, Scri­bo­nius Largus, court physi­cian to the Roman emper­or Claudius, described in his Com­po­si­tiones a method for treat­ing chron­ic migraines: place tor­pe­do fish on the scalps of patients to ease their pain with elec­tric shocks. Largus was on the right path; our brains are com­prised of elec­tri­cal sig­nals that influ­ence how brain cells com­mu­ni­cate with each oth­er and in turn affect cog­ni­tive process­es such as mem­o­ry, emo­tion and attention.

The sci­ence of brain stim­u­la­tion – alter­ing elec­tri­cal sig­nals in the brain – has, need­less to say, changed in the past 2,000 years. Today we have a hand­ful of tran­scra­nial direct cur­rent stim­u­la­tion (tDCS) devices that deliv­er con­stant, low cur­rent to spe­cif­ic regions of the brain through elec­trodes on the scalp, for users rang­ing from online video-gamers to pro­fes­sion­al ath­letes and peo­ple with depres­sion. Yet cog­ni­tive neu­ro­sci­en­tists are still work­ing to under­stand just how much we can influ­ence brain sig­nals and improve cog­ni­tion with these techniques.

Brain stim­u­la­tion by tDCS is non-inva­sive and inex­pen­sive. Some sci­en­tists think it increas­es the like­li­hood that neu­rons will fire, alter­ing neur­al con­nec­tions and poten­tial­ly improv­ing the cog­ni­tive skills asso­ci­at­ed with spe­cif­ic brain regions. Neur­al net­works asso­ci­at­ed with atten­tion con­trol can be tar­get­ed to improve focus in peo­ple with atten­tion deficit-hyper­ac­tiv­i­ty dis­or­der (ADHD). Or peo­ple who have a hard time remem­ber­ing shop­ping lists and phone num­bers might like to tar­get brain areas asso­ci­at­ed with short-term (also known as work­ing) mem­o­ry in order to enhance this cog­ni­tive process. How­ev­er, the effects of tDCS are incon­clu­sive across a wide body of peer-reviewed stud­ies, par­tic­u­lar­ly after a sin­gle ses­sion. In fact, some experts ques­tion whether enough elec­tri­cal stim­u­la­tion from the tech­nique is pass­ing through the scalp into the brain to alter con­nec­tions between brain cells at all.

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