This non-invasive procedure is more effective in people with more preserved brain structure and function | Results open the door to future interventions to improve cognitive ability in a preventive manner in healthy or mildly impaired individuals
Subjective cognitive decline (SCD) is a condition described in people over 60 who do not have a confirmed diagnosis of cognitive impairment but who self-perceive that their abilities have begun to decline. It is a common factor in the preclinical stages of neurodegenerative diseases, when there is no diagnosis yet but changes in the brain have already begun. A study conducted within the framework of the BBHI, published in Frontiers in Aging Neuroscience, has confirmed that transcranial direct current stimulation (TDCS), a non-invasive brain intervention, is able to reduce the natural decline in memory that occurs 30 days after the acquisition of a memory. The treatment is more effective in people with better preserved brain structure and integrity.
TDCS is a brain neuromodulation technique that applies low-intensity electric to the scalp, passing through the skull and modulating the selected brain area.
SCD is considered a risk factor for the development of mild memory impairment and, in the long term, Alzheimer’s disease. “Tools are needed to help enhance the effect of possible interventions, such as pharmacological or psychological interventions in cases where they can be administered,” explains David Bartrés-Faz, leader of the study, Principal Investigator of the BBHI and professor at the Faculty of Medicine and Health Sciences of the University of Barcelona.
Memory formation is a very dynamic process, which implies that for some time after the acquisition of new knowledge, memory remains unstable. The researchers hypothesized that this would open a limited period in which the consolidation of memories could be modified by external interventions, during the so-called “reconsolidation process”. Previous studies indicated that the application of TDCS could be effective for this improvement, but corroborating work was lacking.
The study included 38 participants over 60 years from BBHI’s cohort of more than 5,000 people. The volunteers were asked to recall as many words as possible from a set of 15, and 24h later (day 2) an attempt was made to reinforce their recall by asking them to describe the procedure performed, in the same room and with the same person as the previous day. Then, half of the participants were given real TDCS and the other half a placebo procedure. The next day (day 3) and 30 days after the creation of the new knowledge, everyone was asked again to recall the words they remembered.
The results indicate that the active group, which received real TDCS, recalled an average of 7.2 words on day 30, while the placebo group recalled 5.2. “In other words: the active group experienced a loss of 2 words; while the placebo group lost 4. This indicates that the placebo group loses memory significantly between days 3 and 30, while for the active group this loss is not significant,” explains Lidia Vaqué-Alcázar, first author of the article and postdoctoral researcher at the Department of Medicine, Faculty of Medicine and Health Sciences of the University of Barcelona.
In addition, the study has detected that the favorable response to TDCS occurs more often in people who have their brain structure and function more preserved, with greater cortical thickness and more connectivity between areas related to memory processes. “In contrast, we did not appreciate a relationship between brain state and memory performance in the placebo group. This could be very useful to identify people potentially more susceptible to a better response to treatment,” says Vaqué-Alcázar.
The results support the idea that this combined memory reconsolidation and TDCS protocol could open the door to future interventions to reduce losses in healthy people or those with SCD. Another avenue to explore, for example, is to conduct multiple sessions of TDCS to determine the potential of the intervention as a measure to prevent memory loss beyond day 30.