Virtual reality boosts brain rhythms needed for neuroplasticity, memory

The brain responds differently in immersive virtual reality environments versus the real world, a finding that could help scientists understand how the brain brings together sensory information from different sources to create a cohesive picture of the world around us, according to a new study published in the journal Nature Neuroscience.

Mayank Mehta, PhD, is the head of W. M. Keck Center for Neurophysics and a professor in the departments of physics, neurology, and electrical and computer engineering at University of California Los Angeles. His laboratory studies a brain region called the hippocampus, which is a primary driver of learning and memory, including spatial navigation. To understand its role in learning and memory, the hippocampus has been extensively studied in rats as they perform spatial navigation tasks.

When rats walk around, neurons in this part of the brain synchronize their electrical activity at a rate of 8 pulses per second, or 8 Hz. This is a type of brain wave known as the "theta rhythm," and it was discovered more than six decades ago. Disruptions to the theta rhythm also impair the rat's learning and memory, including the ability to learn and remember a route through a maze. Conversely, a stronger theta rhythm seems to improve the brain's ability to learn and retain sensory information. Therefore, researchers have speculated that boosting theta waves could improve or restore learning and memory functions. But until now, nobody has been able to strengthen these brain waves.

Damage to neurons in the hippocampus can interfere with people's perception of space. The researchers suspected that the theta rhythm might play a role in this perception. To test that hypothesis, researchers invented an immersive virtual reality environment for the rats that was far more immersive than commercially available virtual reality for humans. The virtual reality allows the rats to see their own limbs and shadows and eliminates certain unsettling sensations such as the delays between head movement and scene changes that can make people dizzy. To measure the rats' brain rhythms, the researchers placed tiny electrodes, thinner than a human hair, into the brain among the neurons.

The researchers found the theta rhythm becomes considerably stronger when the rats run in the virtual space in comparison to their natural environment. This discovery suggests that the unique rhythm is an indicator of how the brain discerns whether an experience is real or simulated. Additionally, when the researchers measured activity in the cell body of a rat brain experiencing virtual reality, they found a different electrical rhythm compared with the rhythm in the dendrites. 

They dubbed this never-before-seen rhythm "eta." It turned out this rhythm was not limited to the virtual reality environment: with extremely precise electrode placement, the researchers were then able to detect the new rhythm in rats walking around a real environment. Being in virtual reality, however, strengthened the eta rhythm.

The findings could also pave the way for "virtual reality therapy" for learning and memory-related disorders ranging including attention deficit hyperactivity disorder (ADHD), autism, Alzheimer's disease, epilepsy, and depression, the researchers said.

"This is a new technology that has tremendous potential," he says. "We have entered a new territory."