The 'three Rs' of reading, writing and arithmetic could become four. Random electrical stimulation, a technique that applies a gentle current through the skull, leads to a long-lasting boost in the speed of mental calculations, a small laboratory study of university students has found.
閱讀、寫作和算術（簡稱3R）這三種基本能力有可能變成四個。某個小實驗室對大學生研究發現：對大腦進行隨機電刺激，就是利用弱電流調節大腦皮質神經元活動的技術，可長期提高受試者的心算速度。

      If unobtrusive brain stimulation proves safe and effective in larger classroom trials, the technology could augment traditional forms of study, says Roi Cohen Kadosh, a cognitive neuroscientist at the University of Oxford, UK, who led the study. “Some people will say that those who are bad at mathematics will stay bad. That might not be the case.”

      Cohen Kadosh’s team made headlines in 2010, when it showed that a different form of electrical jolt — transcranial direct-current stimulation (TDCS) — helped volunteers to learn and remember a number system made up of unfamiliar symbols.

In TDCS, electrical current flows continuously between electrodes placed on different parts of the scalp, activating neurons in one area and quieting them in another. It feels like a baby tugging gently on your hair. By contrast, with transcranial random-noise stimulation (TRNS), “people ask ‘are you sure it’s on?’” says Cohen Kadosh. As the name implies, the technique involves electrical currents flowing through electrodes in random pulses, activating neurons in multiple brain areas. There is no evidence to suggest that either method is unsafe, he says.
在經顱直流電刺激（TDCS）研究中，電極安放在頭皮的不同部分，電流穩定持續地在電極間流動，刺激一部分的神經元，又使另一部分的神經元安靜。這感覺就像嬰兒在輕輕拽著你的頭髮，與經顱隨機雜訊刺激（TRNS）相比，人們甚至感覺不到電流的存在，甚至會問“有在通電嗎？”。而顧名思義，經顱直流電刺激就是電流在隨機脈衝中流經電極，啟動多個腦部神經元。Kadosh稱，目前還沒有證據證明這兩種方法的不安全性。

      In the latest study, his team tasked 25 Oxford students with rote memorization of mathematical facts (such as 2 x 17 = 34) and more complicated calculations (for example, 32 – 17 + 5). Thirteen volunteers received TRNS to their prefrontal cortices, a part of the brain involved in higher cognition, while doing these problems for five days in a row. They became faster at both tasks than volunteers in the control group, who were electrically stimulated only briefly.

Surprise test

      The volunteers (and their experimenters) thought that the study would end there. But six months later, Cohen Kadosh’s team got 12 of them back in the lab and tested how quickly and accurately they answered similar maths problems — this time without electrical stimulation.

      The six returning volunteers who had previously received stimulation were on average 28%, or more than a second, faster than the control group at correctly answering the problems involving calculation. When Cohen Kadosh’s team tested them for rote learning, they found no difference between the two groups. The results are published today in Current Biology.

      The researchers also measured the activity of participants’ brains with a tool called near-infrared spectroscopy, which measures changes in blood flow to particular areas of the brain. They found that after six months, prefrontal cortex activity during calculations peaked more quickly in volunteers who had received stimulation than in controls. Cohen Kadosh speculates that the maths improvements are, in part, the result of more efficient cognitive processing.
研究人員也用了一種被稱作近紅外光譜（near-infrared spectroscopy）的技術測量參與者大腦特定區域的血流量變化。他們發現六個月後，當計算達到頂峰時，接受過刺激的志願者大腦的前額葉活動較對照組更為劇烈。Kadosh猜測在一定程度上來說，數學能力的提高是因為更高效的認知能力。

      “The findings are intriguing,” says Daniel Ansari, a cognitive neuroscientist at the University of Western Ontario in London, Canada, but he doesn't find the long-term improvements overwhelming, owing to the small number of volunteers who returned for testing. Ansari adds that the findings should be applied to the classroom with caution. “The training used here is highly contrived and does not resemble the way in which math skills are typically acquired,” he says.
加拿大西安大略大學（位於倫敦市）的認知神經科學家Daniel Ansari稱“這些發現是有趣的”但是他也稱，由於返回測試的人數太少，他還沒有發現可長期改進的決定性意義。Ansari認為出於科學的謹慎態度，這些測試應該用於大教室實驗。畢竟“這次實驗是高度人為的，也不同於數學知識通常的獲取方式。”

      Cohen Kadosh hopes to find funding to test electrical brain stimulation among real pupils in a classroom setting, rather than in a laboratory with students at one of the world’s leading universities. He says that new approaches are desperately needed to help the roughly 20% of children who have significant difficulties learning mathematics.

      The machines that generate TRNS are not yet widely available, but TDCS machines can be had for a few hundred dollars and made for less. Kadosh receives regular e-mails from people asking for advice on brain stimulation, or for explanations as to why it didn’t work for them. He doesn't recommend the approach: “Don’t try it at home,” he says.
生產TRNS的機器尚未普及，但是TDCS 機器僅僅需要幾百美元，甚至更少。Kadosh定期收到人們詢問腦刺激的郵件，或者是要求解釋腦刺激對他們不起作用的原因。可是他並不推薦這種方法，他的建議是“別在家裡嘗試。”