Electrical brain stimulation improved both immediate and long-term memory in elderly volunteers with the benefits lasting for more than a month, in experiments carried out at Boston University.
Robert Reinhart, the project leader, said the findings could form the basis for treatments that do not involve drugs or invasive neurotechnology, to boost the cognitive performance of people developing Alzheimer’s disease and other disorders characterised by failing memory.
The Boston researchers directed weak alternating currents to specific regions of the brain, using electrodes in skull caps worn by the participants. They worked with 150 people aged over 65, who received 20 minutes of stimulus a day over four days and heard lists of words that they were asked to recall.
Short-term or working memory — indicated by the immediate recall of words — improved by 65 per cent after the four days and was still 40 per cent better a month later without further stimulus.
Long-term memory — recalling words minutes or more after hearing them — was 50 per cent better after four days and 37.5 per cent better a month after the last electrical input. Results were published on Monday in the Nature Neuroscience journal.
Reinhart sees non-invasive neurostimulation as a potential treatment for memory loss in older people and particularly in those developing dementia. No adverse side effects were reported, apart from “a bit of itching and tingling sensation for approximately 30 to 60 seconds at the beginning of the stimulation and for 30 to 60 seconds at the end”.
“The work has obvious clinical implications,” he said. “The older people with poor general cognitive functioning coming into the experiment were the individuals who showed the largest improvements during both the intervention and the one-month point. [This] bodes well for transferring this [procedure] over to a proper clinical study in people with Alzheimer’s disease who are suffering from more severe memory impairments.”
Electrical stimulation was aimed at two alternative brain regions: the prefrontal cortex, known to be associated with long-term memory, and the parietal cortex further back in the brain, which is more involved in short-term recall. To create a control group, some volunteers underwent a “sham” or placebo procedure in which they wore the same caps as those undergoing active stimulus but without the electrical stimulation being directed at either brain region. Participants did not know which group they were in.
The researchers then read strings of 20 unconnected words to participants. They examined how likely people were to recognise words heard most recently at the end of the list, which is correlated with short-term memory, or at the beginning of the list read to them minutes earlier, which is an indicator of long-term memory.
Masud Husain, a neuroscience professor at Oxford university who was not involved in the research, said “these are very exciting results” but pointed out that the trial was limited in scope. “We have to bear in mind that the effects on memory were of the order of remembering three or four more words out of a list of 20 but this improvement was detectable one month after stimulation, which is quite remarkable.
“Whether these improvements would occur for everyday memories, rather than just lists of words, remains to be tested,” he added.
Reinhart said the Boston University team now intended to focus their work on “real-world” cognitive activities. “What we’re involved in now is relating our laboratory brain and behavioural measures to functional outcomes like . . . measures of activities of daily living,” he said. “[They] are more relevant for reducing the severe social and economic impact of impaired cognition that comes with age and mental illness.”
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