A non-canonical visual cortical-entorhinal pathway contributes to spatial navigation

Spatial navigation depends on anchoring internal spatial maps to external environments, guided by sensory cues such as visual and tactile stimuli. The Medial Entorhinal Cortex (MEC) is crucial for integrating these sensory inputs during the formation of spatial maps. While the responsiveness of many spatial-coding cells to visual stimuli is well-established, the role of tactile sensation in spatial representation is less understood. Rodents primarily gather tactile information through their whiskers, which provide essential spatial and textural details via whisking movements, potentially vital for constructing accurate spatial map. In our study, we employed advanced miniature two-photon microscopy to monitor neural activity in the MEC of freely moving mice subjected to sensory deprivation. Our findings revealed that head direction cells and border cells exhibited impaired spatial representation after either light deprivation or whisker trimming. In contrast, grid cells and speed cells were less affected by whisker trimming compared to visual deprivation, suggesting a stronger dependence on visual cues for these cell types. Notably, distinct subpopulations within each type of spatial-coding cell exhibited varying sensitivity to sensory deprivation-some neurons significantly changed their spatial-coding patterns, while others remained unaffected. This indicates that cells within the MEC may differ in their spatial-coding based on their sensitivity to external sensory inputs. Additionally, we observed a strong correlation between the activity of certain MEC neurons and whisker movement. Collectively, these findings enhance our understanding of how the MEC processes spatial information, particularly in relation to tactile sensation.

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Task and Behavior-Related Variables Are Encoded by the Postrhinal and Medial Entorhinal Cortex During Non-Spatial Associative Learning

Nystuen,

Rogge,

Aasen

et al. 2024

Preprint

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The medial entorhinal cortex (MEC) is pivotal in spatial computations and episodic memory. In particular, an animal’s position can be decoded from the activity of entorhinal grid cells. However, it remains elusive whether MEC could play a more general role in different types of associative learning and how the representations develop during the learning process. It has been shown that the postrhinal cortex (POR), which is directly connected to MEC, integrates visual stimuli with salient outcomes. Here, we use a non-spatial visual association task to investigate whether MEC neurons represent low-level visual cues during learning. Using a Go/NoGo visual association task, we recorded neural activity in MEC and POR throughout the learning phase as mice associated drifting gratings with rewarded, aversive, or neutral outcomes.Our findings reveal that the neural tuning curves in both the POR and MEC change with the learning of the task. From the start of training, the POR neurons exhibited response tuning to the visual cues, and the tuning was stable to cue orientations during learning. In contrast, MEC neurons did not initially respond very strongly to visual cues but developed a robust tuning toward the rewarded trials. While the MEC’s representation of visual information was limited, it encoded other task elements. A large fraction of the neurons formed distinct functional clusters that were either activated or suppressed by reward-related behavior. Remarkably, these clusters segregated anatomically in MEC and maintained strong within-cluster correlations before and after training. Notably, although the same functional clusters were apparent in the POR, they did not show any anatomical structure as in the MEC. Task reversal induced significant changes in network responses across both regions, with a decrease in overall task-responsive neurons but a slight increase in stimulus representation. Strikingly, information about the choice to lick emerged with learning in both brain areas, and most significantly within the functional cell clusters representing reward consumption and plus-cue stimulus. Our results demonstrate that although neurons in MEC and POR develop behavior-modulated tuning during learning of a non-spatial visual association task, the MEC exhibits stronger within-cluster correlations and anatomical organization. Conversely, the POR population exhibits less structural organization and more specific stimulus-tuning, which is reflective of being a higher visual association area. Our findings reveal that the MEC can encode task– and behavior-related variables beyond spatial information.

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A non-canonical visual cortical-entorhinal pathway contributes to spatial navigation

Cited by 3 publications

References 78 publications

The medial entorhinal cortex encodes multisensory spatial information

The medial entorhinal cortex encodes multisensory spatial information

Differential Impact of Multiple Sensory Deprivation on Spatial-coding Cells in Medial Entorhinal Cortex

Task and Behavior-Related Variables Are Encoded by the Postrhinal and Medial Entorhinal Cortex During Non-Spatial Associative Learning

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