If you’re like most people, you may find yourself struggling to recall the exact title of a favorite book, the name of a familiar actor on television, or your latest online banking password. As much as we’re afraid to face it, our memories begin to decline after our mid-20s — and the speed and accuracy at which they function will continue to slip throughout our lives.
Our working memories are particularly vulnerable to this decline — that part of memory associated with linguistic processing and decision-making, which has a limited capacity. This is why you tend to have trouble recalling what you had for lunch yesterday — since its high speed processing requires that it regularly dump out the unimportant data.
Now, scientists have an approach that could work to keep your working memory sharp — at least to an extent. Think of memory as a grand piano with wires in need of tuning. Recent models of the memory circuits show that memories are dependent on a far reaching network in the brain as we conjure up familiar images, sounds, and smells. The signals travel at a slow frequency with theta waves — think of them like the chords of a stringed instrument when struck, but moving a bit more slowly when they resonate.
The new therapy, a type of noninvasive electrical stimulation known as tACS, or transcranial alternating current stimulation, assumes that regularly strumming these chords would gradually throw the system out of tune, and so targets the circuits of the memory network that drift apart.
The findings were described in the journal Nature Neuroscience, and hope to be used to treat memory loss due to head trauma, simple age-related decline, and perhaps could even delay the onset of dementia. The study shows how such a therapy could gain support, but a clinical version of tACS is probably some years away from becoming a reality, as neuroscientists assess the full risks and benefits involved.
The new study conducted by neuroscientists Robert M.G. Reinhart and John A. Nguyen of Boston University, utilized two test groups — one group of young adults as well as a group of people in their 60s and 70s. The first step was to analyze the neural firing rhythms on each subject. This allowed them to determine how to best optimize tACS on each subject, fine-tuning the crosstalk between the frontal and temporal cortex areas on each brain, where working memory is processed. The subjects then endured a 25-minute period of gentle electrical stimulation through a skullcap with built-in electrodes. After their treatment, the patients were given a series of memory tests, and the older group performed just as well as their younger counterparts.
A series of tests were given both before and after the treatment — in which the participants were given an image to look at and determine if it was the same as an image they were shown later or if they could point out minimal differences. To be sure that the subjects weren’t performing better simply because they believed the treatment was working, the researchers administered two trials of it — one in which the subjects received a placebo treatment and another in which they received tACS.
After the placebo trial, the younger group performed better on the memory test — but following the tACS trials, both groups performed equally well. The researchers tested continuously for 50 minutes and did not notice a decline in working memory throughout the duration of the study. Further experimentation showed that they could also muddle the memory chords in younger participants by using tACS to decouple circuits.
“We show here that working memory decline in people in their 60s and 70s is due to brain circuits becoming uncoupled, or disconnected,” said Reinhart, during a conference call. “Negative, age-related changes in working memory are not unchangeable. We can bring back the superior function you had when you were much younger.”
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