Work memory restored in the elderly by electrical stimulation

According to a new study published April 8 in Nature Neuroscience (1), scientists have discovered that a periodic electrical discharge can help offset memory deficits in older people. Researchers at Boston University focused on working memory, the part of the short-term memory tasked with temporarily storing information. And an essential component of reasoning and decision-making.

How does age affect working memory?

Brain neurons generate electrical waves that store information for as long as necessary. Although information is only stored for a few seconds, short-term memory is essential for performing daily tasks, including reading, writing, and even counting. Scientists believe that millions of neurons in the brain cooperate to accomplish short-term memory processes.

Although scientists have previously reported differences in brain activity by age, it is still unclear how these differences relate to cognitive performance (2). But they could be related to the decoupled activity of electric waves in different parts of the brain in the elderly.

Nevertheless, memory loss is an "essential characteristic" of cognitive decline in the elderly. With age, electrical impulses that control brain waves become less coordinated, resulting in short-term memory deficits.

Increase working memory with electrical stimulation

Scientists have previously reported an increase in working memory using electrical stimulation. However, this is the first time this approach has been demonstrated in an older population.

Researchers used what is called transcranial AC stimulation to synchronize the brain waves of 42 healthy volunteers aged 60 to 76 years. Low electrical impulses synchronize two areas of the brain involved in cognition, the prefrontal cortex and the temporal cortex.

At the same time, they recorded the brain waves of the participants before and after the stimulation using electroencephalographic (EEG) measurements. Then, to test changes in cognitive performance, participants were asked to spot differences in sets of images before and after electrical stimulation.

After only 25 minutes of electrical stimulation, older participants identified the differences more accurately and their performance was comparable to that of a much younger test group composed of healthy adults aged 20 and over. years. The positive effects lasted throughout the test – almost an hour – but can last even longer. In addition, previously desynchronized electrical impulses in the prefrontal and temporal cortex began to be synchronized.

Interestingly, researchers were also able to reduce the working memory of younger participants by using electrical stimulation to desynchronize brain impulses.

Future implications

The new study has effectively demonstrated that brainwaves can affect the working memory of older people. Importantly, he "laid the groundwork for future non-pharmacological interventions targeting aspects of cognitive decline," the authors write.

The researchers have shown no evidence of the potential clinical benefits of using this approach for the time being. However, they hope to further explore technologies such as this one as potential treatments for work-related diseases such as Alzheimer's disease.

(1) Reinhart, R.M.G. and Nguyen, J.A. Working memory is reactivated in the elderly by synchronizing the rhythmic brain circuits. Nature (2019). DOI: 10.1038 / s41593-019-0371-x

(2) Grady, C. The Cognitive Neuroscience of Aging. Nature Reviews Neuroscience (2012). DOI: 10.1038 / nrn3256