Why The Brain Can't Make Sense Of VR (Study)

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Why The Brain Can't Make Sense Of VR (Study)
September 18, 2016

It seems like a reasonable question: Does the brain, physiologically speaking, experience virtual worlds differently? After all, we’re attuned to sensory inputs not as discrete packages, but as entire suites involving subtle combinations of senses intermingling with memories. Compared to computers, we are not so easily tricked.
 
This is the basic question posed in a new paper published in this week’s edition ofNature Neuroscience. Courtesy of a team of brain scientists based at UCLA and led by physicist and neurobiologist Mayank Mehta, the study concludes that, yes, at least in terms of spatial mapping and memory-making, our brains handle virtual worlds very differently than real worlds. This may have big implications.
 
Mehta and his team studied the hippocampus, the region of the brain implicated in depression and schizophrenia, but also memory creation and spatial awareness. The brain is constantly making maps of its surroundings, and this is where those guides are created. And yet, for neuroscientists, the process is (ahem) uncharted territory. The basic set-up involves a rat in a tiny rat harness Being subjected to what amounts to a tiny rat IMAX movie. The general idea is simple enough: The brain is constantly in the process of computing distances between it and various surrounding landmarks. This is not strictly a visual process, however: Other senses provide subtle cues that go into navigation. It’s less obvious, but smells and sounds can make a whole lot of difference.
 
As the paper explains, experiments have so far been unsuccessful in fully differentiating the visual part of spatial awareness from the multisensory whole. And the problem is still deeper—there’s a sort of “inner” sense of movement called theta-phase precession as well as proprioception, a sense of movement derived from physical exertion as related to the relative positions of various body parts.
 
One experiment in 2008 found that rats running on a hamster wheel experienced activity in the map-making brain even though their visual cues remained the same. The actual visual part of navigation appears to be much, much smaller than once assumed.
 

The problem is that spatial awareness is usually studied using virtual reality. Yes, neuroscientists send rats through virtual mazes and it’s probably even weirder than you might imagine. The basic set-up, and the one used in the current study, involves a rat being put into a tiny rat harness and then subjected to what amounts to a tiny rat IMAX movie. The rat's neurological activity is then recorded as it moves through a virtual one-dimensional maze. The activity is also recorded as the same rat moves through a proper, real-world maze.
 
The general finding is this: “Under these [VR] conditions, hippocampal neurons show only weak spatial selectivity, an observation that is at apparent odds with the high spatial selectivity seen in studies in freely behaving rodents,” Mehta and his team write. “The virtual reality system we have used is quite sophisticated, far more immersive than most systems used by humans,” Mehta told me. “So, the reasons for these differences are not likely to be technological weaknesses.”
 
Those difference were actually enormous. The rats running the VR maze had hippocampal neurons firing almost completely randomly—the neurological definition of being lost as shit. "We do believe that as we add more multisensory stimuli or features to virtual reality, it will feel more and more real. The ‘map’ disappeared completely,” Mehta offered. “Nobody expected this. The neuron activity was a random function of the rat’s position in the virtual world.”
 
The findings may have implications well beyond spatial awareness and on into memory itself. As Mehta explains, human memory speaks two distinct languages, one of brain activity rhythms and the other of brain activity intensity. The patterns formed are deeply complex.
 
In the virtual world, the rats experienced similar activity rhythms as in the real world, but the intensity patterns were complete nonsense. The basic effect of the virtual reality world is to simulate the neurological conditions that might be experienced in memory and learning disorders. This insight is a good thing, as neuroscientists move closer and closer toward effective treatments for those disorders.
 
Virtual reality isn’t hopeless either. “We do believe that as we add more multisensory stimuli or features to virtual reality, it will feel more and more real,” Mehta said. “As virtual reality become more realistic, the brain's responses too will become more like those in the real world. The need to repair memories is enormous,” the neuroscientist added. “The goal is to understand how these different, multisensory features influence neural responses and memory.”

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