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Does electrical stimulation of the brain improve our memory ?

Memory deteriorates with age. Memory deficits impair general abilities that we urgently need in our daily lives. Those neuronal networks that underlie these abilities have been identified in more detail in recent years. Several studies suggest that the rhythmic activity of cognitive circuits are important for the coordination of information processing. We assume a capacity-limited working memory for short-term storage of information and an unlimited long-term memory for permanent storage.

Now, in a search for technologies to enhance the rhythmic activity of the circuits underlying these two memory stores, Robert Reinhart, neuroscientist at Boston University in Massachusetts (U.S.A.), and his colleagues have shown that an improvement in memory performance is achieved when the brain is repeatedly treated with weak electrical currents over several days. As they demonstrated in the prestigious journal Nature Neuroscience, this effect lasts for up to one month.

In this study, electrical currents were delivered via electrodes on the scalp using a non-invasive method of stimulating the brain called transcranial alternating current stimulation (tACS). Via changes in amplitude, frequency, and relative phase shift of the current flow, rhythmic activity in the brain was directly modified.

During the 20-minute stimulation, the 150 subjects, aged between 65 and 88, performed a memory task in which they were asked to recall lists of 20 words that were read aloud. They then had to recall as many words as possible from memory.

Previous studies had shown that long-term memory and working memory, which the brain uses to store information only temporarily, are controlled by different mechanisms. Based on this research, stimulating the dorsolateral prefrontal cortex, a region at the front of the brain, with high-frequency electrical currents improved long-term memory, while activating the inferior parietal lobe, located further back in the brain, via low-frequency electrical currents improved working memory.

After repeated treatment, those participants who received high-frequency stimulation of the dorsolateral prefrontal cortex better remembered the words mentioned at the beginning of the lists, thus increasing their long-term memory. In contrast, low-frequency stimulation of the inferior parietal lobe improved the participants' ability to remember words appearing later in the lists, particularly affecting working memory. The subjects' memory performance improved over the course of four days and was still detectable one month later. Those participants who had the lowest general cognitive abilities before the study increased their memory the most.

Changing stimulation frequencies and brain regions (e.g., activating the parietal lobe with high frequencies) or using a "sham protocol" in which electrical currents were applied only briefly at the beginning and end of the task to mimic the sensation of brain stimulation, did not improve memory performance. This demonstrates the specificity of the stimulation protocols used.

The results are of great interest in light of a rapidly aging world population. Impairment of basic memory functions, which are essential for activities of daily life such as making financial decisions or understanding language, also places a burden on our health and social systems. If anything, the likelihood of such impairments has increased during the coronavirus pandemic. Reinhart and colleagues are therefore working hard to translate the benefits of brain stimulation to other types of memory tasks and to stabilize improvements in memory performance over time.


Grover S, Wen W, Viswanathan V, Gill CT, Reinhart RMG (2022) Long-lasting, dissociable improvements in working memory and long-term memory in older adults with repetitive neuromodulation. Nature Neuroscience 25:1237

Rogers J (2022) A frequency location to remember. Nature Reviews Neuroscience 23:644

Image credit: iStock/wildpixel


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