MEDIAL ENTORHINAL CORTEX NEURONS FLEXIBLY UTILIZE VISUAL AND TACTILE CUES FOR SPATIAL CODING

Accurate spatial navigation depends on the integration of self-generated signals and external sensory inputs. The medial entorhinal cortex (MEC) contains multiple types of spatially-modulated cells and plays a critical role in spatial navigation. While visual cues are well established as supporting spatial representations, the contribution of tactile cues remains poorly understood.
Here, we examined how MEC neurons utilize visual and tactile information to maintain spatial maps. In a well-lit environment rich in visual cues, both darkness and whisker trimming disrupted head direction tuning and border cell firing in the MEC, whereas grid cells and non-grid spatially-modulated cells were primarily impaired by darkness. We next tested whether mice could form spatial maps in complete darkness in the absence of visual cues but with abundant tactile information. Under these conditions, all classes of spatially-modulated cells established stable tuning maps across days based solely on tactile cues, and whisker trimming markedly degraded spatial tuning across all cell types, including grid cells. These results indicate that the MEC flexibly integrates available sensory inputs to support spatial coding.
Given the diversity of tactile sources, we further attenuated tactile input from the paws by removing dominant floor textures and eliminated physical contact with environmental boundaries by removing the walls. Under the latter manipulation, all border cells lost their boundary tuning, and grid cells as well as other spatially-modulated cells were severely disrupted. Together, these findings reveal a critical role of tactile cues—particularly boundary-related information—in maintaining spatial representations in the MEC during navigation.