Electrical stimulation gives significant memory boost to elderly

Electrical stimulation of the human brain can produce a striking improvement in the short-term memory of the elderly, with people in their 60s showing memory functions equivalent to volunteers 40 years younger, US research has shown.

“These findings show us that age-related decline is not unchangeable,” said Robert Reinhart, head of the Visual Cognitive Neuroscience Laboratory at Boston University who lead the study. “We can bring back the superior working memory you had when you were much younger. This is important because the global population is rapidly ageing and elderly people struggle with many activities that depend on their memory.”

The research, published in Nature Neuroscience, compared the short-term memory of 42 healthy volunteers aged 60-75 with the same number in their 20s. As expected, the older participants performed more slowly and less accurately on computer-based memory tests, which required them to spot the difference between pictures presented three seconds apart.

The researchers measured the participants’ brainwaves — oscillations between the brain’s prefrontal and temporal regions — through electroencephalography (EEG) caps and then stimulated their brains with an electrical current through electrodes applied to the scalp. The alternating frequency was tuned to match each volunteer’s brainwaves, in order to help synchronise the electrical activity within his or her brain.

While receiving this stimulation for only 25 minutes the older participants’ speed and accuracy improved markedly, making them perform as well as the twenty-somethings. The improvement lasted for almost an hour after the current was switched off. “We just recorded for 50 minutes in the experiment but my suspicion is that the effect lasts potentially for hours,” said Dr Reinhart.

Although other research has demonstrated memory improvement through electrical or magnetic brain stimulation, none has given such strong or statistically secure results. Even so, neuroscientists who were not involved in the Boston study urged caution in interpreting the results.

The larger your memory deficit, the more room there is for improvement through brain stimulation. It is possible to turbocharge normally functioning people, including young people

“It is a proof-of-concept study conducted on neurologically normal volunteers doing a lab-based experiment, and it would be premature to extrapolate the findings to everyday functioning in individuals with clinically significant memory problems,” said Dorothy Bishop, neuropsychology professor at the University of Oxford. “Considerably more research would need to be done before concluding that this method had clinical application.”

However, Dr Reinhart said he was convinced that helping to synchronise electrical activity across different brain areas could be used to treat a range of neurological disorders. “The larger your [memory] deficit, the more room there is for improvement through brain stimulation,” he said. “But it is possible to turbocharge normally functioning people, including young people.”

One area to which the research could be applied is treating people with Alzheimer’s disease. Sara Imarisio, head of research at the charity Alzheimer’s Research UK, said: “Research is beginning to investigate whether electrical stimulation of certain brain regions can help improve people’s memory and thinking.

“What makes this study intriguing is that it tests a non-invasive approach, unlike previous research in this area which has often studied direct brain stimulation through invasive implants.”

Dr Reinhart’s team has also demonstrated, in unpublished research, the opposite effect: desynchronising brain activity by administering alternating current at a different frequency. This might help to treat other brain diseases such as epilepsy where — unlike Alzheimer’s — there is too much connectivity between different brain regions.