Combining VR and non-invasive brain stimulation to boost spatial memory without surgery

by Ecole Polytechnique Federale de Lausanne Setup of the experiment.(A) Spatial navigation task. Each block started with an encoding period during which participants were consecutively presented with three objects at specific locations and asked to memorize their position. After encoding each object multiple times, a cue was shown during the retrieval phase with the image of one of the objects and the participant had to navigate to the location of the object. (B) Temporal interference stimulation concept. Two pairs of electrodes are placed on the head and deliver two HF currents I1 and I2 at a frequency f1 and f2 = f1 + Δf, respectively. On the bottom of the panel, the combination of the two fields is shown with high envelope modulation inside the target region and low envelope modulation outside. (C) Theta burst protocols. A specific shift in frequency between the two signals was applied with a specific timing to mimic either iTBS or cTBS. During iTBS, central panel, trains of 2 s are applied every 10 s, each one composed of 10 bursts at 5 Hz. Each burst is composed of three pulses at 100 Hz. In the 8-s break, no shift is applied between the two sources, leading to a flat envelope. During cTBS, bursts at 5 Hz are applied continuously without breaks. The bursts are composed of three pulses at 100 Hz as for the iTBS protocol. Credit: Science Advances (2024). DOI: 10.1126/sciadv.ado4103 As we age, it becomes more difficult to remember where things are—whether it’s recalling where we left the keys or where we parked the car. This spatial memory deteriorates further with the onset of dementia, a condition that someone in the world develops every three seconds, according to Alzheimer’s Disease International.

Researchers at two EPFL labs have joined forces to give a boost to spatial memory by creating a unique experimental setup that combines non-invasive deep- brain stimulation , virtual reality training , and fMRI imaging—all housed within Campus Biotech in Geneva. Published in Science Advances , the study demonstrates that targeted, painless electric impulses to the hippocampus and adjacent structures, a deep brain region implied in memory and spatial navigation, can improve the brain’s ability to recall locations and navigate more effectively.

“By finding ways to improve spatial memory without surgery or medication, we are addressing a serious concern for a large and growing population: the elderly, as well as brain trauma patients and those affected by dementia,” says Friedhelm Hummel, head of the Hummel Lab.

The study is the result of a collaboration between the Hummel Lab and Olaf Blanke’s Laboratory of Cognitive Neuroscience (LCNO), both at EPFL’s Neuro X institute. By combining Hummel’s expertise in non-invasive brain stimulation with Blanke’s cognitive research of spatial navigation in virtual reality environments, the researchers developed a unique neuro-technological setup. A one-of-a-kind combination of neuro-technologies

The experiment began with researchers placing four harmless electrodes on the heads of healthy individuals to stimulate the hippocampus and adjacent structures. This non-invasive technique, called transcranial temporal interference electric stimulation (tTIS), sends targeted pulses without causing any discomfort for the participant.

Next, volunteers are immersed in a virtual world using VR goggles. Building on previous research by co-first-author Hyuk-June Moon, the scientists tasked the participants with navigating through a series of locations and remembering key landmarks. This immersive virtual setting allowed the researchers to precisely measure how well participants could recall and navigate spatial information while receiving tTIS.

“When stimulation was applied, we observed a clear improvement of the participants’ recall time—the time it took to start moving toward where they remembered the object to be,” says Elena Beanato, the other first author of the study. “This leads us to believe that by stimulating the hippocampus, we temporarily increase brain plasticity, which when combined with training in a virtual environment , leads to better spatial navigation.”

The entire experiment was conducted within an fMRI scanner. This provided researchers with real-time images of brain activity, allowing them to monitor how the hippocampus and surrounding regions responded to tTIS during the spatial navigation tasks. The fMRI data revealed changes in neural activity associated with the observed behavioral changes, specifically in the regions responsible for memory and navigation, giving the researchers deeper insight into how non-invasive stimulation modulates brain function.

This integration of advanced technologies at EPFL’s Neuro X Institute makes Campus Biotech one of the few places where all three experimental techniques can be combined in a single study.

“The alliance of tTIS, virtual reality, and fMRI offers a highly controlled and innovative approach to studying the brain’s response to stimulation and its impact on cognitive functions,” adds Blanke. “In the long term, we envision using this approach to develop targeted therapies for patients suffering from cognitive impairments, offering a non-invasive way to enhance memory and spatial abilities.”

More information: Elena Beanato et al, Noninvasive modulation of the hippocampal-entorhinal complex during spatial navigation in humans, Science Advances (2024). DOI: 10.1126/sciadv.ado4103

Provided by Ecole Polytechnique Federale de Lausanne

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