Grid cell signals are introduced to mitigate spatial aliasing in geometrically ambiguous environments and indicate that grid cells provide information complementary to boundary-based inputs, yielding more reliable place representations in geometrically ambiguous environments.
Abstract
Spatial aliasing occurs when two or more distinct locations produce highly similar place-cell representations, primarily due to environmental symmetry or repetitive structures. This issue is most pronounced when place representations are constructed solely from boundary vector cell (BVC) inputs, because symmetric or repetitive structures can yield indistinguishable sensory patterns across multiple locations in an environment. This work introduces grid cell signals to mitigate spatial aliasing in such settings. Because grid cells contribute periodic, internally generated spatial signals that vary independently of environmental geometry, they play a key role in disambiguating perceptually identical locations. We integrate multiple modules of analytically constructed grid cells with BVC-driven place cells and show that this leads to a 94--99% reduction in spatial aliasing relative to a BVC-only baseline across three environments: an open environment without obstacles; an environment with a cross-shaped central obstacle creating high visual symmetry; and a maze environment. The greatest improvement occurs in the environment with the highest visual symmetry. These results indicate that grid cells provide information complementary to boundary-based inputs, yielding more reliable place representations in geometrically ambiguous environments.
Digital navigation systems facilitate goal-directed travel but reduce active engagement with the surrounding environment—a process critical for the formation of allocentric cognitive maps. Neuroscientific evidence reveals that spatial orientation relies on the coordinated activity of specialized spatially tuned neuronal populations, including place cells, head direction cells, grid cells, and border cells. This article introduces the specific properties of these spatially tuned cells, which encode central components of spatial information such as position, direction, distance, boundaries, and object relationships. Cell activities are continuously modulated by the perception of stable landmarks and environmental boundaries. This could form the basis for a “neurocartographic” approach that focuses on the systematic use of these cell activities to support spatial orientation. Enhancing the visual salience of landmarks and boundary structures, as well as integrating Virtual Reality (VR) and Augmented Reality(AR)-based components, may strengthen the metric representation of space—particularly grid cell–based coding. The overarching objective of this approach is to promote the development of allocentric and egocentric spatial representations during both real-world navigation and map-based wayfinding, thereby counteracting the decline in navigational abilities observed with the widespread use of digital turn-by-turn systems.
Frank Dickmann, Annika Korte, Denise O´Meara et al.· KN - Journal of Cartography...· 0 citations
The medial entorhinal cortex (MEC) has classically been viewed as a spatial coding region, but growing evidence indicates that it also contains temporal representations. However, how spatial and temporal codes are organized within the MEC remains unclear. Here we recorded MEC neurons with high-density silicon probes while mice performed a MEC-dependent timing task and a virtual reality spatial navigation task in a similar head-fixed setup. We found that spatial and temporal representations were partially overlapping but systematically biased across the MEC population. Grid cells and non-grid cells with strong spatial tuning were less likely to show reliable time-locked activity during the timing task. In contrast, neurons with weaker spatial tuning more flexibly shifted their coding scheme to temporal coding during timing task. Moreover, spatial tuning strength and its negative relationship with temporal tuning were preserved in a distinct open field environment, indicating that the coding preferences of individual neurons are constrained by a stable network-level organization. Together, these findings suggest MEC is organized along a coding gradient, ranging from dedicated stable spatial coding neurons to more flexible spatial or temporal coding neurons which represent information according to cognitive demands.
Hyun-Woo Lee, John C. Bowler, James G. Heys· bioRxiv· 0 citations
Digital maps increasingly replace paper maps because they are accessible, regularly updated, and customizable. Yet they often weaken spatial orientation skills and create technological dependency. One possible solution is supporting navigation without extra cognitive effort by designing maps that address spatially responsive brain cells. These cells are thought to be involved in the construction of an internal spatial representation. As animal studies have shown that the perception of environmental boundaries contributes to the stabilization of firing behavior, we examined boundary effects on path integration (PI) in screen-based and virtual reality (VR) settings. This allowed us to test whether the effect is robust across formats with different immersion and self-motion feedback. Participants completed PI tasks in a virtual arena while viewing a briefly displayed elevated line, wall, or no artificial boundary. It was expected that perceived boundaries would stabilize the activity of spatially responsive cells, such as grid cells. This is likely to contribute to a reduction in PI errors. Results showed a supportive tendency for the line condition, whereas the wall condition produced the highest errors. This pattern was comparable across both media. The findings suggest that the effect of spatial boundary cues depends on their design and perceptual properties.
Denise O’Meara, Julian Keil, C. Oster et al.· ISPRS International Journal...· 0 citations
Segregating objects from one another and the background is essential for perception. In natural scenes, it is common to encounter spatially separated stimuli, such as distinct figure-ground regions, adjacent objects, and partial occlusions. Neurons in the mid- and high-level visual cortex have large receptive fields (RFs) that often encompass multiple, spatially separated stimuli. It is unclear how neurons represent and segregate multiple stimuli within their RFs and the role of spatial cues. We recorded neuronal responses in middle–temporal (MT) cortex of male rhesus macaques to spatially separated random-dot stimuli that moved simultaneously in two directions. We found that across motion directions, responses to bidirectional stimuli were systematically biased toward the component located at the neuron's preferred RF subregion. The sign and magnitude of this spatial-location bias were predicted by the neuron's spatial preference for single stimuli presented in isolation. The bias persisted when attention was directed away from the RF, changed predictably when the motion border shifted within the RF, and developed over time, indicating a stimulus-driven spatial weighting mechanism. Bidirectional responses were well described by a spatial preference-weighted normalization model, in which the responses elicited by individual components are weighted and combined according to the neuron's spatial preference. Bidirectional stimuli also reduced model-inferred gain variability, suggesting potential engagement of response-stabilizing mechanisms. These results show that MT neurons capitalize on RF spatial selectivity to represent multiple motion components. Across a neuron population with diverse spatial preferences, this coding strategy provides a neural substrate for segregating spatially separated moving stimuli.
Steven Wiesner, Bikalpa Ghimire, Xin Huang· Journal of Neuroscience· 0 citations
In rodents, hippocampal activity is classically described in terms of position-anchored place cells, whereas nonhuman primate work has emphasized spatial view cells, in which activity depends on the region of space being viewed. This contrast has fueled a longstanding debate over whether primate and rodent spatial codes are biologically distinct. We recorded single units in the hippocampus of macaques as they navigated linear tracks in two visually distinct contexts, intermittently making context-dependent object choices. Using a generalized linear model to dissociate position coding from spatial view coding, we identified three coexisting populations in the macaque hippocampus: Position cells, View cells, and Conjunctive cells encoding both variables. Position cells were prevalent and showed rodent-like properties—localized firing, directional tuning, and contextual remapping—even after accounting for visual sampling, whereas View cells stably encoded allocentric visual space. Population decoding confirmed this dissociation at the ensemble level. Robust position codes thus coexist with, yet remain dissociable from, view codes in the primate hippocampus, suggesting that the apparent scarcity of place-like responses in earlier primate work reflects methodological and task-related differences rather than a fundamental species-level divergence.
Seuk-Hwan Shin, Heung-Yeol Lim, Su-Min Lee et al.· bioRxiv· 0 citations
The dentate gyrus (DG) is thought to play a key role in the formation of dissociable memory representations for similar contexts. Neurons in the DG receive highly processed spatial and nonspatial sensory information from the medial and lateral entorhinal cortices, respectively. Changes in spatially tuned firing patterns of DG place cells occur after spatial changes to an environment, but the degree to which DG place cells respond to ethologically relevant nonspatial stimuli is largely unknown. Spatial and nonspatial information is thought to be transmitted to the DG during discrete local field potential events called dentate spikes. Here, we tested the extent to which different spatial and nonspatial stimuli modulate place cell firing patterns and dentate spike dynamics. We performed extracellular recordings of DG place cells and local field potentials in rats of both sexes exploring a familiar spatial environment, in which social stimuli and nonsocial odors of varying ethological relevance were presented, and a novel spatial environment. As expected, DG place cells exhibited different firing patterns between familiar and novel environments. Significant changes in firing were not observed, however, with any of the nonspatial stimuli. Surprisingly, the occurrence of dentate spikes associated with lateral entorhinal cortex input increased during exploration of ethologically relevant stimuli, and this increase was greater for social stimuli. Altogether, these results suggest that the DG preferentially responds to social stimuli at the network level, providing novel insights into how spatial and nonspatial information is processed in the DG.
Peyton G. Demetrovich, L. Colgin· Journal of Neuroscience· 0 citations
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