Can a declining memory be improved? Many research groups are trying to find the answer to this question. Electrical brain stimulation is now showing encouraging results in a study.
In older people, electrical brain stimulation can improve both short-term and long-term memory. This is the result of a fundamental work for which tests were carried out on women and men of retirement age. Seniors with 20 minutes of brain stimulation on four consecutive days were able to recall significantly more words from a list than people in a control group. The improvement was still clearly measurable after one month. The study by a group led by Robert Reinhart and Shrey Grover from Boston University in Boston (Massachusetts, USA) has been published in the journal "Nature Neuroscience".
"A critical factor contributing to age-related costs is impairment of basic memory systems, which are essential for activities of daily living, such as making financial decisions or understanding language," the researchers write. They investigated whether memory performance can be improved with the help of transcranial alternating current stimulation (tACS). tACS uses special alternating electrical currents to stimulate changes.
In the tests, 60 seniors between the ages of 65 and 88 were put on hoods with electrodes that can conduct weak electrical currents to the subjects' scalps. The researchers divided the study participants into three groups: In the first group, the lower parietal lobe (inferior parietal lobe), which has an important function in short-term memory, was stimulated. In the second group, the currents were for the superior lateral frontal lobe (dorsolateral prefrontal cortex), which is important for long-term memory. The third group received no stimulation and served as a control group.
In the experiment, the subjects heard 20 words, which they were then asked to repeat. There were five runs of this task, and the procedure took about 20 minutes in total. The scientists carried out the experiment on four consecutive days. As early as the second day, the group whose long-term memory had been stimulated showed better performance in recalling the first words on the list; this performance increased in the following days.
The group with the short-term memory stimulation achieved a clearly better performance in recalling the last words on the list from the third day. However, these results only occurred when the brain region responsible for short-term memory was stimulated at a frequency of 4 hertz and the region for long-term memory at a frequency of 60 hertz.
In addition, the improvement effect was still evident when trying again after one month. The improvement was greater the worse the subject had performed on memory tests before the start of the experiments. Reinhart, Grover and colleagues suggest investigating whether such noninvasive stimulation might be helpful in patients with certain memory deficits and at risk of dementia.
Johannes Levin from the German Center for Neurodegenerative Diseases (DZNE) in Munich sees an interesting approach in the study. However, it only leads to alleviation of symptoms, not to combating the cause of memory deficits. He is critical of a possible application in dementia patients: "We must not forget that the brains of dementia patients are pathologically different from those of healthy people."
Walter Paulus, professor emeritus for clinical neurophysiology at the University Medical Center Göttingen, considers the after-effects to be "considerable" after a month. However, the stimulations would probably be much more expensive than drugs with comparable effects because of the personnel costs.
(This article was first published on Monday, August 22, 2022.)