Researchers observed the activity of grid cells in the human brain when self-position illusions were triggered by multisensory virtual reality without changing visual perspectives.

Dr. from the Bionic Research Center of the Korea Institute of Science and Technology (KIST). Hyuk-Jun Moon, Prof. from the Swiss Federal Institute of Technology Lausanne (EPFL). In collaboration with Olaf Blanke’s team, he successfully created the illusion of self-location. . He observed corresponding changes in the activity of cells in the human brain grid using multisensory virtual reality (VR) in an MRI scanner.

The brain is known to contain grid cells and place cells that function as a global positioning system (GPS), allowing us to understand where we are. While traveling to a certain location, GPS cells are triggered sequentially according to their location along the way, and these cells play an important role in recognizing our location as coordinates and remembering events in space.

Problems with previous studies

People can sometimes feel like they are somewhere else without actually moving their physical body, such as during an illusion such as an out-of-body experience. However, such purely cognitive changes in self-location (and the corresponding response of the brain’s GPS cells) have not been studied in animal models such as mice, where these perceptions cannot be elicited or verified.

Additionally, traditional methods used to study GPS cells required opening the skull and measuring the activity of individual cells in deep brain structures with invasive electrodes, limiting our understanding of human GPS cells.

To observe grid cell activity during illusory changes in their position, the researchers combined MRI-compatible virtual reality technology with multi-sensory body stimulation to create the illusion of being precisely controlled in different directions as designed. fMRI images measured during the experiment were used to assess grid cell activity, and participants’ subjective illusory experience was assessed using post-experiment questionnaires and behavioral measures reflecting their perceived self-position.

In conclusion, the team demonstrated for the first time that purely cognitive changes in magnetic positions, illusory changes in self-position, triggered by multisensory bodily stimulation, without any changes in visual environmental cues, evoke corresponding activity in human retinal cells.

This is the first clinical study to show that multisensory bodily stimuli alone can evoke retinal cell activity without any navigation (not active or imaginary) and without a change in visual perspective. It shows that GPS coordinates in the human brain respond not only to the physical location of the body but also to location information based on various cognitive actions and experiences, increasing the possibility of objectively diagnosing hallucinatory symptoms using brain imaging analysis. The findings are also expected to contribute to the development of new treatments by providing targets for the treatment of patients suffering from delusional symptoms such as out-of-body experiences.

Dr. “Unlike previous studies of the human cellular network that relied on changes in environmental visual cues from a first-person perspective, we recently proposed a key element of the study regarding the integration of multisensory bodily signals,” Moon said. “We plan to conduct further international collaborative research to better understand the brain mechanisms underlying delusions caused by various psychiatric and neurological diseases and to develop non-invasive brain stimulation techniques that may alleviate these symptoms.”