Tuning brain regions like radios for better memory

Our brains are basically electrochemical computers, so using electricity to manipulate their function is a well-proven technique. From deep-brain stimulation that controls the symptoms of depression to zapping our grey matter to improve our vision, electrical current applied to our brains holds a lot of promise. Now researchers at Imperial College London have shown that a low-voltage stream of electricity can be used to bring different brain regions in sync with each other, leading to improved memory ability and the hope of treating neurological disorders.

In the study, the researchers used what's known as transcranial alternating current stimulation (tACS) to affect the way in which the electric current in two brain regions was oscillating. The weak electric current applied to the forehead from tACS brought the middle frontal gyrus and the inferior parietal lobule into sync with each other. Both of these areas are known to be involved in working memory, which is our extreme short-term memory that helps us function in the here-and-now. An example of working memory would be the way in which we'd be able to recall what we needed when we go out to our cars to retrieve a forgotten item.

To test the effects of the brain-tuning process, 10 subjects were made to participate in a memory task that increased in difficulty. They were asked to identify if a number that appeared on a computer screen was the same as the previous one (easy) or as the one that had been shown two screens earlier (harder).

During the memory tests, tACS was applied in a way that either synced the brain regions to the theta frequency or kept them out of sync. The researchers found that when the regions were oscillating together, the reaction times of the more difficult tasks improved. In fact, the tasks were accomplished just as quickly as the easier ones.

This isn't the first time tACS has been shown to improve memory. Last year, a group of men were given the electrical stimulation while sleeping. That study that found that when the current was delivered at the same oscillations known as sleep spindles, memory improved. Additionally, a means of influencing the brain called transcranial magnetic stimulation has also been shown to boost memory generally and, in a study earlier this year, demonstrated its effectiveness in sharpening specific memories when its electromagnetic signal was delivered in a highly focused manner.

The researchers now plan to see if their technique can improve the function of patients with brain impairments.

"The next step is to see if the brain stimulation works in patients with brain injury, in combination with brain imaging, where patients have lesions which impair long range communication in their brains," says Ines Ribeiro Violante, a neuroscientist in the Department of Medicine at Imperial who led the research. "The hope is that it could eventually be used for these patients, or even those who have suffered a stroke or who have epilepsy."

The work of the team has been published in the journal eLife.

Source: Imperial College London