The scenes and the environments in World of Warcraft games appear so real that, for a moment, you forget you are staring at the screen. Technology has advanced so much that we can not only recreate reality but also engage with it. But however real the virtual may seem, the brain knows the difference! According to the recently published findings, the neurons in the brain react differently when they perceive a virtual environment than when they are in the real world.

The GPS Cells in Our Brains

The clue to the brain’s varied responses to different environments lies in the “GPS” or place cells. These neurons in the hippocampus create and control cognitive maps by taking input from the environment. They fire when a person is in a novel environment to create episodic memories that help us remember events (what) and place these events in their appropriate contexts of space (where) and time (when).

Place cells are critical for learning and memory. Incidentally, the hippocampus region is damaged in people with Alzheimer’s disease, schizophrenia, epilepsy, post-traumatic stress disorder or in those who have suffered strokes. Because their ability to learn and recall events, people, and objects is severely impaired, these people find it challenging to move about and around the world.

How Do GPS Cells Behave in Real and Virtual Environments?

The modus operandi of the space-mapping neurons in the hippocampus is not wholly clear, but scientists have deciphered that these cells form mental maps of environments by registering the position of different objects in an environment to calculate distances between them.

However, they believe that apart from the visual-spatial stimuli, the smells and sounds present in an environment also go into the creation of mental maps. This may be the reason why the place cells behave differently in real and virtual environments because the computer-simulated reality does not provide varied sensory stimuli.

Because human and rodent neurons are similar, scientists have carried out tests on the hippocampal cells of rats to arrive at the above conclusions. Here’s how all the findings add up.

According to a study published last year, a place cell in the hippocampus fires or “lights up” (as evident from scan images) whenever the rat is in a new environment. A real environment contains many different sensory cues including distal visual and self-motion cues. However, a virtual environment contains only distal visual and non-vestibular self-motion cues. Experiments on rats in these two environments showed that only 20 percent of the place cells in their brains got activated in a virtual environment compared to 45 percent when they were placed in a similar-looking but real world. This indicates that apart from behaving differently in real and virtual worlds, the brain creates more effective and comprehensive cognitive maps when it is fed with multi-sensory cues.

The above experiment sheds light on other interesting goings-on in the hippocampus in real and virtual environments.

When the rats were in the real world, their place cells fired every time they passed an object (a fixed landmark). This occurred consistently, and scientists realized that the neural place cells probably create mental maps by computing the distance between objects. But when the rats were in a virtual environment, not only fewer place cells in their brains fired but they acted randomly as well. In the experiment, the place cells were activated based on the movements or the relative positions of the rats. For instance, the cells lit up whenever the rats paced five steps back and forth, irrespective of the landmarks they perceived.

Another curious finding came out from a similar experiment. When the rats were made to navigate the real world, the activity within the place cells that fired in response to environmental stimuli correlated with the speed at which the animals moved. The faster the rats moved, the greater was the activity in these cells and vice versa. In the virtual environment, a screen showing video of the real world moved in tandem with the rats to give them the perception that they were actually moving as they do in the real world. But their hippocampal place cells showed steady, rhythmic activity irrespective of the speed at which the rats changed their relative positions. This discrepancy indicates the brain does not register stimuli accurately in a virtual environment.

Scientists believe that a cognitive map of a virtual world should be a function of the relation between specific motion paths and peripheral landmarks. But experiments have proved otherwise. This clearly suggests that the brain recognizes the gaps between the real world and the virtual reality our technologies create.

What Do Scientists Make of the Brain’s Different Performances in Real and Virtual Worlds?

The hippocampus is involved in spatial learning and related memory formation. The above experiments throw some light on how the brain works to create and retrieve memories. These findings bring hope that the mysteries of the hippocampus will one day be decoded and therapeutic procedures will be devised to enhance the quality of life of patients suffering from neurodegenerative disorders.

The above experiments also take some of the shine away from virtual reality technologies. For all the hype, it is obvious that the virtual is not as “real” as it is made out to be, at least as of yet.

Computers cannot recreate the “feel” of the real world — the smell of freshly-baked bread wafting through the air, the rustle of leaves in the breeze, and the crunching of gravels under the feet. Computer programmers and analysts may be concerned. After all, the closer virtual reality is to reality, the more accurate would be the performance of the critical job-related simulation applications used by military personnel, aviators, and scientists.

References

Aghajan, Z., Acharya, L., Moore, J., Cushman, J., Vuong, C., & Mehta, M. (2014). Impaired spatial selectivity and intact phase precession in two-dimensional virtual reality Nature Neuroscience, 18 (1), 121-128 DOI: 10.1038/nn.3884

Aikath, D., Weible, A., Rowland, D., & Kentros, C. (2014). Role of self-generated odor cues in contextual representation Hippocampus, 24 (8), 1039-1051 DOI: 10.1002/hipo.22289

Geisler, C., Robbe, D., Zugaro, M., Sirota, A., & Buzsaki, G. (2007). Hippocampal place cell assemblies are speed-controlled oscillators Proceedings of the National Academy of Sciences, 104 (19), 8149-8154 DOI: 10.1073/pnas.0610121104

Jadhav, S., Kemere, C., German, P., & Frank, L. (2012). Awake Hippocampal Sharp-Wave Ripples Support Spatial Memory Science, 336 (6087), 1454-1458 DOI: 10.1126/science.1217230

Nitz, D. (2014). A place for motion in mapping Nature Neuroscience, 18 (1), 6-7 DOI: 10.1038/nn.3908

Ravassard, P., Kees, A., Willers, B., Ho, D., Aharoni, D., Cushman, J., Aghajan, Z., & Mehta, M. (2013). Multisensory Control of Hippocampal Spatiotemporal Selectivity Science, 340 (6138), 1342-1346 DOI: 10.1126/science.1232655

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