New clues about how the brain processes the body in space has lead to a discovery about why sometimes our spatial perception is disturbed and we lose our sense of direction—giving new meaning to the phrase “I can’t hear myself think.”
Researchers recruited sixty healthy adults, both young and old, to wear virtual reality goggles while moving around a digital environment while also having to move their bodies along physical mazes. They were assisted through the maze by being led by the hand of one of the research assistants. Throughout the process, the study participants were asked to tell the assistant how far they believed they had traveled from the starting point.
The participants had to rely on their other senses to estimate where they were in relation to the starting point in the actual physical environment because their vision was obscured by the virtual setting that they were experiencing through the goggles. The researchers were testing a phenomenon called “path integration” to determine how well the body was able to keep track of itself and its movements within the physical plane.
With complex mathematical modeling, the researchers identified that the brain goes through a series of glitches which can be likened to noise or interference. This noise is described as an internal noise that derails information processing when the brain is trying to perceive its position from tracking its movement.
Younger adults were better at tracking their movements than older participants because the level of internal “noise” increased within the brain as it ages. The researchers demonstrated that most of the participants, regardless of age, were able to determine where they were in relation to the starting point illustrated in their body rotation. Most of the participants could use information about where they were in the room just a few moments before to tell them where they were in relation to the starting point.
Further research into where the “noise” is coming from and why it progressively becomes louder with age is the next step of understanding why spatial awareness, getting lost, and the aging brain are connected. Neurodegenerative diseases often start with getting lost in familiar places or forgetting where things were left.
A previous study about how the brain perceives its location due to a newly discovered type of brain cell called the grid cell is becoming better understood with this concept of noise disturbing the sense of direction. Grid cells (which are technically neurons) have unpredictable firing patterns in the brains of older adults, but the researchers of this study suggest that it isn’t due to a defect of the grid cells. They believe that this internal noise is disrupting the signals that are being sent to the grid cells.
Matthias Stangl, Ingmar Kanitscheider, Martin Riemer, Ila Fiete, Thomas Wolbers. Sources of path integration error in young and aging humans. Nature Communications, 2020; 11 (1) DOI: 10.1038/s41467-020-15805-9