DEVELOPMENT OF A MULTIMODAL VR SYSTEM FOR CORTICAL FUNCTIONAL NETWORK ANALYSIS DURING MOUSE SOCIAL BEHAVIOR
Authors: Suzuki *Mao , Nakai Nobuhiro , Osumi Noriko , Takumi Toru 
Published: February 2025

Abstract

Background
Social behaviors such as social communication and interaction are generally observed in animals. During social interaction, we receive external sensory stimuli that induce different sensory modalities, such as vision, hearing, touch, and smell. The information from these sensations is integrated and processed in the brain to generate behavioral outputs in social behavior. However, visualizing multisensory integration processes as brain activity at the network level during behavioral states remains a technical challenge.

Aims & Objectives
This study aims to develop a multimodal virtual reality (VR) system to elucidate the neural mechanism of information processing of multimodal social stimuli based on functional network analysis in mice.

Method
We constructed a multimodal VR system for investigating the functional cortical network during the sensory perception of social-related stimuli. The VR system allowed a pair of the head-fixed mice to explore the three-dimensional open-field-like virtual environment projected on a screen by moving on the treadmill. We designed a mouse avatar as a social visual cue combined with urine odor from male mice as a social olfactory cue in VR. We used an object model (similar in color and size to the mouse avatar) with neutral odors (non-attractive and non-aversive for mice) as a control non-social stimulus. The two paired subject mice can interact with each other as an avatar or object combined with or without odor cues in VR environments. When interacting, an air-puff stimulus is presented as a tactile sense to the whiskers of subject mice. We examined GCaMP6f-expressing mice using the VR system. The cortical activity of behaving mice was measured by transcranial mesoscopic calcium imaging. We analyzed the functional cortical network in a one-second time window by calculating the correlation coefficient of calcium signal changes between cortical areas in social and non-social conditions.

Results
In the VR environments, the mice showed an increased tendency to social interaction behavior and decreased distance to paired mice in the social condition compared with the non-social condition. We observed that cortical activity change after social interaction significantly increased compared to the non-social condition. We analyzed the functional cortical network for two seconds before and after the social interaction to examine cortical states for approach behavior and response to interaction. Significant alterations in the functional cortical network were observed in the social condition during active, but not passive, interactions.

Discussion & Conclusion
Our study aimed to visualize multisensory integration processes in the cortex at the network level during social behavior. We found that the cortical functional network was significantly altered in social and non-social conditions.These results suggest that although similar behavioral expressions, such as when mice actively interact with each other, the sensory processing in the cortex differs in social and non-social conditions.
Furthermore, this system can visualize cortical network dynamics during social behavior in mouse models of autism, schizophrenia, and depression. Examination of cortical networks in the model mice in social behavior will contribute to elucidating pathological mechanisms of the disorders.