Study Suggests Well-Timed Electrical Brain Stimulation Boosts Memory

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Brain implants designed to improve brain functionality aren’t new, but they’re all firmly within the experimental stages at present. Just last month, for example, a very small study suggested that surgically implanted electrodes slowed down the progression of Alzheimer's in some people.

Now, a new Nature Communications study, led by the University of Pennsylvania, has suggested that a similar type of brain implant can also boost memory. Unlike the aforementioned study, this new research venture recruited those suffering from epilepsy.

As first spotted by The New York Times, this trial of 25 patients concluded that intermittent electrical stimulation to a specific part of the brain can improve a patient’s word recall by 15 percent, a fairly modest but nevertheless significant amount. Before we explore what the study actually involved, though, it’s important to manage our expectations somewhat.

Evidence linking electrical stimulation of the brain to improved memory is somewhat mixed. Even a quick look at the scientific literature over the past few years throws up a variety of contrary results of such techniques: back in 2016, a study in Neuron suggested electrical stimulation did not improve a person’s memory, whereas a 2017 Current Biology study found the opposite.

Trials tend to be very small-scale, and it could be argued that, in many cases, enough data yet to suggest whether or not the positive effects are genuine or simply a placebo effect. Normally, only people with certain neurological conditions are used in these trials, and often, other non-human primates are used, rather than people – a useful, but not ideal, proxy.

That most recent study, which used three Alzheimer’s patients, fell on the positive side of things, but several neuroscientists criticized it for being having a small sample size. This latest study, featuring 25 people, is an improvement, but it’s still small.

At this point, far more data is needed, but each study is welcome. So what did this new one find, exactly?

These epilepsy patients were being assessed for a future operation, meaning that electrodes were already being slipped into their brain to see what type of probing can cause or prevent seizures. As plenty are placed in the memory centers of the brain, this provided the team with a good chance to test out their new device.

Rather than send continuous pulses of electricity into the brain, it operated when it detected a lull in the brain’s memory storage abilities, and shut off when it registered when it was working well. The patients couldn’t feel when the device was on or not; it caused no pain or any physical sensation at all.

Using word recall tests – reading through a list of words and trying to remember them a bit later – they found that patients did around 15 percent better at the tests when the implant was active.

The ability of the device to respond to specific brain states is known as a “closed-loop design.” Other papers attempting the same memory-boosting feat tended to use open-loop designs, those that use continuous, high-frequency stimulation.

The red circle, the left lateral temporal cortex, was the target of this study. University of Pennsylvania

The team’s Department of Defense-funded paper explains that the “literature shows that direct open-loop stimulation of the hippocampus and medial temporal lobes is unlikely to reliably improve memory.” They state that their closed-loop device, which targets the left lateral temporal cortex, has “provided proof of concept for the therapeutic treatment of memory dysfunction.”

Again, it’s early days. Far more data is required before any firm conclusions are made, and remember, this trial only involved people with epilepsy.

Although agreeing that this work still involved a small sample size, Dr Mark Dallas, Lecturer in Cellular and Molecular Neuroscience, University of Reading, told IFLScience that “this is a more robust study than the previous [Alzheimer’s] study.”

He added, however, that “without the relevant controls, this could be a placebo effect.”

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