Findings highlight multisensory interactions in the human brain

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Gravity is the unseen force that dominates our entire lives. It's what makes walking uphill so difficult and what makes parts of our body eventually point downhill. It is unyielding, everywhere, and a force that we battle with every time we make a move. But exactly how do people account for this invisible influence while moving through the world? A new study in Frontiers in Neuroscience used virtual reality to determine how people plan their movements by "seeing" gravity using visual cues in the landscape around them, rather than "feeling it" through changes in weight and balance. PhD Student Desiderio Cano Porras, who worked in Dr. Meir Plotnik's laboratory at the Sheba Medical Center, Israel and colleagues found that our capability to anticipate the influence of gravity relies on visual cues in order for us to walk safely and effectively downhill and uphill. In order to determine the influence of vision and gravity on how we move, the researchers recruited a group of 16 young, healthy adults for a virtual reality (VR) experiment. The researchers designed a VR environment that simulated level, uphill, and downhill walking. Participants were immersed in a large-scale virtual reality system in which they walked on a real-life treadmill that was at an upward incline, at a downward decline, or remained flat. Throughout the experiment, the VR visual environment either matched or didn't match the physical cues that the participants experienced on the treadmill. Using this setup, the researchers were able to disrupt the visual and physical cues we all experience when anticipating going uphill or downhill. So, when participants saw a downhill environment in the VR visual scenery, they positioned their bodies to begin "braking" to go downhill despite the treadmill actually remaining flat or at an upward incline. They also found the reverse - people prepared for more "exertion" to go uphill in the VR environment even though the treadmill remained flat or was pointing downhill. Related Stories