Virtual Reality Boosts Brain Rhythms Crucial for Neuroplasticity, Learning and Memory

AHA Publisher — Wed, 14 Jul 2021 00:50:23 +0000

University of California – Los Angeles Health Sciences via EurekAlert – A new discovery in rats shows that the brain responds differently in immersive virtual reality environments versus the real world. The finding could help scientists understand how the brain brings together sensory information from different sources to create a cohesive picture of the world around us. It could also pave the way for “virtual reality therapy” for learning and memory-related disorders ranging including ADHD, Autism, Alzheimer’s disease, epilepsy and depression. 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 UCLA. 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. “If that rhythm is so important, can we use a novel approach to make it stronger?” asks Dr. Mehta. “Can we retune it?” Damage to neurons in the hippocampus can interfere with people’s perception of space – “why Alzheimer’s disease patients tend to get lost,” says Dr. Mehta. He says he suspected that the theta rhythm might play a role in this perception. To test that hypothesis, Dr. Mehta and his colleagues invented an immersive virtual reality environment for the rats that was far more immersive than commercially available VR for humans. The VR 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. “Our VR is so compelling,” Dr. Mehta says, “that the rats love to jump in and happily play games.” To measure the rats’ brain rhythms, the researchers placed tiny electrodes, thinner than a human hair, into the brain among the neurons. “It turns out that amazing things happen when the rat is in virtual reality,” says Dr. Mehta. “He goes to the virtual fountain and drinks water, takes a nap there, looks around and explores the space as if it is real.” Remarkably, Dr. Mehta says, the theta rhythm becomes considerably stronger when the rats run in the virtual space in comparison to their natural environment “We were blown away when we saw this huge effect of VR experience on theta rhythm enhancement,” he says. This discovery suggests that the unique rhythm is an indicator of how the brain discerns whether an experience is real or simulated. For instance, as you walk toward a doorway, the input from your eyes will show the doorway getting larger. “How do I know I took a step and it’s not the wall coming at me?” Dr. Mehta says. Answer: The brain uses other information, such as the shift of balance from one foot to the other, the acceleration of your head through space, the relative changes in the positions of other stationary objects around you, and even the feeling of air moving against your face to decide that you are moving, not the wall. On the other hand, a person “moving” through a virtual reality world would experience a very different set of stimuli. “Our brain is constantly doing this, it’s checking all kinds of things,” Dr. Mehta says. The different theta rhythms, he says, may represent different ways that brain regions communicate with each other in the process of gathering all this information. When they looked closer, Dr. Mehta’s team also discovered something else surprising. Neurons consist of a compact cell body and long tendrils, called dendrites, that snake out and form connections with other neurons. 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. “That was really mind blowing,” Dr. Mehta said. “Two different parts of the neuron are going in their own rhythm.” The researchers 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 VR, however, strengthened the eta rhythm – something no other study in the past sixty years has been able to do so strongly, either using pharmacological tools or otherwise, according to Dr. Mehta. Previous studies have shown that the precise frequency of the rhythm makes a big difference to neuroplasticity, he says, just as the precise pitch of a musical instrument is critical for creating the right melody. This opens up an unprecedented opportunity to design VR therapy that can retune and boost brain rhythms and as a way to treat learning and memory disorders. “This is a new technology that has tremendous potential,” he says. “We have entered a new territory.” To read the original article click here.

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A New Discovery: How Our Memories Stabilize While We Sleep

AHA Publisher — Fri, 25 Oct 2019 07:00:14 +0000

CNRS via EurekAlert – The authors here looked more closely at what happens during delta waves themselves. They discovered, surprisingly, that the cortex is not entirely silent but that a few neurons remain active and form assemblies, i.e. small, coactive sets that code information. Scientists at the Center for Interdisciplinary Research in Biology (CNRS/Collège de France/INSERM)[1] have shown that delta waves emitted while we sleep are not generalized periods of silence during which the cortex rests, as has been described for decades in the scientific literature. Instead, they isolate assemblies of neurons that play an essential role in long-term memory formation. These results were published on 18 October 2019 in Science. While we sleep, the hippocampus reactivates itself spontaneously by generating activity similar to that while we are awake. It sends information to the cortex, which reacts in turn. This exchange is often followed by a period of silence called a ‘delta wave’ then by rhythmic activity called a ‘sleep spindle’. This is when the cortical circuits reorganize to form stable memories. However, the role of delta waves in the formation of new memories is still a puzzle: why does a period of silence interrupt the sequence of information exchanges between the hippocampus and the cortex, and the functional reorganisation of the cortex? Related Articles: Repairing DNA Damage Through Sleep How Memories Form and Fade The authors here looked more closely at what happens during delta waves themselves. They discovered, surprisingly, that the cortex is not entirely silent but that a few neurons remain active and form assemblies, i.e. small, coactive sets that code information. This unexpected observation suggests that the small number of neurons that activate when all the others stay quiet can carry out important calculations while protected from possible disturbances. And the discoveries from this work go even further! Spontaneous reactivations of the hippocampus determine which cortical neurons remain active during the delta waves and reveal transmission of information between the two cerebral structures. In addition, the assemblies activated during the delta waves are formed of neurons that have participated in learning a spatial memory task during the day. Together these elements suggest that these processes are involved in memory consolidation. To demonstrate it, in rats the scientists caused artificial delta waves to isolate either neurons associated with reactivations in the hippocampus, or random neurons. Result: when the right neurons were isolated, the rats managed to stabilise their memories and succeed at the spatial test the next day. These results substantially change how we understand the cortex. Delta waves are therefore a means of selectively isolating assemblies of chosen neurons, which send crucial information between the periods of hippocampo-cortical dialog and the reorganisation of cortical circuits, to form long-term memories. To read the original article click here.

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Virtual Reality Boosts Brain Rhythms Crucial for Neuroplasticity, Learning and Memory

A New Discovery: How Our Memories Stabilize While We Sleep