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SLaunching electric current in the brain for just 25 minutes reversed the decline in working memory associated with aging, scientists said Monday. Although researchers have tested the effects on people for only 50 minutes, this discovery offers hope for a reinforcement of a mental function so essential to reasoning, problem-solving and planning, that it has been called the foundation of intelligence.
By stimulating the brain in specific areas of AC, "we can bring back the higher memory function you had when you were much younger," Robert Reinhart, a psychology researcher, told reporters. "Negative changes related to age [in working memory] are not immutable. "
In order for the alternating current, delivered by electrodes embedded in a skull cap, to be used to treat deficits in the working memory, it will however have to overcome a long list of obstacles, starting with the proof of its safety. But whether the results published in Nature Neuroscience or not lead to practical applications, they provide some of the strongest evidence to date of why older people are not as good at remembering a number of phone that we just heard or address in a fair place. text seen: the brain circuits become functionally disconnected and fall out of sync.
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"This is a rigorous and well-designed study," said neurophysiologist Michael Nitsche of the German University of Göttingen, who reviewed the paper for the journal. "It adds important information about the causal relevance of the modifications of [brainwaves] for cognitive decline related to age, and this shows that these alterations are reversible. "
Working memory is the sketch of the mind, where the information – which it has just acquired or derives from the long-term memory – is weighed, considered, manipulated and introduced into cognitive tasks, ranging from the follow-up from a conversation to mental arithmetic. The brain writes on this sketchbook the oscillations of the neuronal shots, called brain waves, which transmit signals inside and between the prefrontal cortex of high level thinking and the temporal lobes, harboring the hippocampus memorizing.
For their experiments, BU scientists tested the working memories of 42 younger adults (aged 20 to 29) and 42 adults (60 to 76 years old). People saw an image of an accordion, for example, and 3 seconds later, they saw it or something else, and then they were asked to indicate it 's They had already seen it before. Older adults responded correctly about 80% of the time and the youngest at 90%. While people were (presumably) trying to remember the accordion, EEGs monitored their brain waves, finding much less synchronization of oscillations in older adults than in younger ones.
The young participants then had a sham stimulation with an alternating current – they wore a cap with electrodes but no current – while the older adults had the real deal, in each case, for 25 minutes. There is a tingling, but only for about 30 seconds, and no one can distinguish the factice current from the real kind.
For a real AC, the frequency was tuned to the individual brain, in correspondence with its natural oscillations, so as to synchronize brain waves which, as people age, seem to be out of sync. "We can grant [the stimulation] at your frequency, your sweet spot, "Reinhart said.
Almost immediately, the accuracy of the elderly has improved. He quickly reached 90% of their younger counterparts and maintained this level for 50 minutes after stopping the stimulation, when scientists stopped taking action. EEG showed that in the elderly, brain waves between the temporal cortex and the prefrontal cortex exhibited the same degree of synchrony as in the younger ones.
Precision in treated seniors did not decrease after 50 minutes, Reinhart said, "I guess [the effect] lasts more than 50 minutes and possibly a few hours. "
The idea that brain wave synchronization is the basis of working memory goes back at least 20 years and many laboratories have found evidence that specific frequency oscillations are required for working memory. "It is thought that the cell populations that synchronize their activity are transferring information," said Reinhart – for working memory, from temporal regions to the prefrontal cortex.
After alternating synchronism between the prefrontal cortex and the temporal lobes, alternating brain waves (about eight cycles per second worked very well), "these two areas are talking to each other," he said. "We are resynchronizing these areas of the brain."
Other laboratories have also shown that electrical stimulation of the brain can improve memory. In a study conducted in 2018, the current of electrodes implanted in the brains of people with epilepsy improved memory by 15%. A study funded by the Pentagon Defense Advanced Research Projects reported last year that a "human memory prosthesis" – electrodes implanted in the hippocampus – improved up to 35% memory short-term (similar to working memory) and long-term memory. or so in eight people with epilepsy.
It's definitely an experience "do not try this at home". Further research will be needed to determine whether AC stimulation can sustainably improve working memory, how often it should be given, what objectives and frequency are optimal, and whether the work of the artificial lab results in benefits. real. "I would not exclude [durable improvement] completely, "said Göttingen's Nitsche." Advanced stimulation protocols can have longer-term effects and work needs to be done to identify optimized protocols "and test their safety.
In Reinhart's study, the older the memory of the elderly, the better it was by AC stimulation. But even among young adults with good memory, "we are seeing an increase in brain and behavior measurements," he said of unpublished results. "I think it's possible to turbocharge" their memory, too.
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