Researchers from the Shenzhen Institute of Advanced Technology (SIAT) of the Chinese Academy of Sciences (CAS) and their collaborators have uncovered the coding principle underlying self-centered (egocentric) representation for spatial perception.  

The study was published in Neuron on Dec. 14. 

Our understanding of the intricate mechanisms for spatial perception in the human brain has recently advanced with the discovery that self-centered perception of external items is closely integrated with our world-centered understanding of the world, which is the brain's internal "GPS" system. However, given the vast number of items surrounding us, how the brain codes the diverse items remains a mystery. Wang's team delves into this problem by investigating the processing of environmental boundaries and virtual landmarks by the retrosplenial cortex, a brain area central to navigation and memory. The results offer a new understanding of the principle for coding objects in an egocentric coordinate system. 

The encoding of external objects based on an egocentric (subjective perspective) frame of reference is crucial for navigation, as most sensory stimuli are represented in this coordinate system (e.g., object A is in front of you). Well-known place cells, grid cells, and head direction cells encode from a world-centered (allocentric) perspective, defining location and direction based on a behavioral arena-defined frame of reference. However, allocentric coding is built upon the computation and transformation of egocentric representation. Although there have been studies on egocentric representations in brain regions surrounding limbic navigation and memory systems, little is known about how egocentric encoding processes different objects in the same or different scenes. 

The researchers employed in vivo two-photon microscopy during an open-field navigation task to investigate the egocentric representation of environmental boundaries in spines and dendrites, whose activity patterns reflect the functional properties of presynaptic and postsynaptic sides, respectively. The results revealed functional clustering in dendrites with significant egocentric tuning, suggesting the existence of specialized channels for processing egocentric information about boundaries, likely through egocentric boundary cells. To examine if these cells also represent other items in different contexts, they compared the egocentric representation of multiple items during two pairs of tasks: the open field task paired with a virtual reality task. They found that the boundary-representing cells are largely independent of the visual landmark-representing cells. 

Significantly, this research also contributes to the understanding of Alzheimer’s disease, a neurodegenerative disease. The retrosplenial cortex, a key area in this study, is known to be affected in Alzheimer's disease, impairing patients' navigation abilities.  

Thus, these findings not only enhance the knowledge of spatial perception but also offer insights into the potential neural mechanisms underlying spatial perception deterioration in pathological conditions. 

Media Contact:
ZHANG Xiaomin
Email:xm.zhang@siat.ac.cn