Mice in virtual space: Hungarian researchers discover new mechanisms of vision with their own VR device

The cortical representation of behavior and perception is one of the key areas of scientific research, as it lays the foundation for a deeper exploration of brain mechanisms and the discovery and development of related therapeutic strategies. To understand these phenomena at the level of individual cells, the most suitable method is to examine mice's brain activity using real-time 3D imaging. However, in such studies, it is particularly important to ensure that the mouse's head remains completely stable, as movement can compromise the accuracy of the results. Researchers typically address this by fixing the mouse's head and employing virtual reality systems.

Over the past 20–30 years, neuroscientists, pharmaceutical companies, and corporations have developed numerous virtual reality tools to study the vision of experimental animals. These tools, however, typically used two-dimensional projections to represent virtual spaces, assuming that experimental animals, like humans, could reconstruct the surrounding 3D reality from two-dimensional images, such as humans do for the flat image of a television screen. Researchers from HUN-REN IEM, BVC, the Institute of Molecular and Clinical Ophthalmology Basel, and Pázmány Péter University have demonstrated that this assumption is incorrect. For rodents, two-dimensional projections do not provide a realistic experience, potentially distorting results. This was illustrated by Gergely Dobos and his colleagues with a simple but striking example: mice crossed a virtual abyss displayed on traditional VR screens without hesitation. In contrast, they immediately stopped and even retreated when the abyss was presented using the Moculus system.

"The project has proven that mice can only perceive the world in three dimensions if virtual reality is projected in a realistic way tailored to their vision. Unlike humans, mice lack sufficient capacity for abstract visual thinking, making it essential for what they see to faithfully reflect reality," explained Gergely Szalay, lead researcher at HUN-REN IEM and BVC.

The Moculus VR system consists of a specialized treadmill that records and transmits data on the mouse's movements, two screens, and a corresponding optical imaging system. The latter provides mice with a field of vision exceeding 180 degrees, enabling them to interact naturally with the virtual environment. Meanwhile, researchers can map the mouse's brain activity patterns using two-photon microscopy, offering valuable insights into how animals learn and the neural mechanisms that regulate decision-making. These studies not only aid in understanding fundamental brain functions but also contribute to the development of therapeutic solutions for neurological disorders, such as vision impairment.

"Rodents' visual learning abilities are surprisingly advanced. Contrary to previous assumptions, they can acquire new visual information in as little as one day, or sometimes even just 30 minutes. This means that rodents learn more than a hundred times faster with Moculus compared to earlier virtual reality systems, which required 5–9 days of training. By reducing the difficulties and artifacts associated with lengthy training periods, Moculus is revolutionizing the study of visual learning mechanisms, enabling discoveries even during a single short training session," explained Linda Judák, lead researcher at HUN-REN IEM and BVC.

One of the device's greatest advantage is its ability to identify complex brain activity patterns related to learning, including so-called anticipatory neuronal signals that appear even before the presentation of visual stimuli. Moreover, with the help of this tool, researchers have also discovered new, previously unknown neural network mechanisms emerging during visual learning.

The developed device has generated significant interest in the field of neuroscience research tools, as no similar solution is currently available on the market. Among its many advantages is its compact, modular design, which allows it to be easily integrated with any electrophysiological or imaging equipment, such as two-photon microscopes.

"Three years ago, at the end of 2021, during the establishment of the BrainVisionCenter, Botond Roska and I defined, as our main mission, basic research in vision restoration, the development of specialized research tools required for this, and cortical vision restoration related research . Moculus represents an important milestone in these efforts, as it allows the cortical role of the genetic engineering methods developed by Botond and his team to be tested more effectively than ever before," emphasized the director.

The device is closely aligned with the mission of the BrainVisionCenter (BVC), founded by Botond Roska and Balázs Rózsa, which focuses on developing therapies for vision restoration and treatments for central nervous system diseases. The development was led by Linda Judák, Gergely Szalay, Gergely Dobos, and Balázs Rózsa, who studied the plasticity of the visual cortex in mice during rapid learning. The significance of their research is highlighted by the fact that their study was published in Nature Methods, one of the world's most prestigious scientific journals.