Dataset Information

Environmental Barriers Disrupt Grid-like Representations in Humans during Navigation.

ABSTRACT: Environmental barriers fundamentally shape our behavior and conceptualization of space [1-5]. Evidence from rodents suggests that, in contrast to an open-field environment, where grid cells exhibit firing patterns with a 6-fold rotational symmetry [5, 6], barriers within the field abolish the 6-fold symmetry and fragment the grid firing fields into compartmentalized repeating "submaps" [5]. These results suggest that barriers may exert their influence on the cognitive map through organization of the metric representation of space provided by entorhinal neurons. We directly tested this hypothesis in humans, combining functional MRI with a virtual navigation paradigm in which we manipulated the local barrier structure. When participants performed a fixed-route foraging task in an open field, the functional MRI signal in right entorhinal cortex exhibited a 6-fold periodic modulation by movement direction associated with conjunctive grid cell firing [7]. However, when environments were compartmentalized by barriers, the grid-like 6-fold spatial metric was abolished. Instead, a 4-fold modulation of the entorhinal signal was observed, consistent with a vectorized organization of spatial metrics predicted by rodent models of navigation [5]. Collectively, these results provide mechanistic insight into why barriers compartmentalize our cognitive map, indicating that boundaries exert a powerful influence on the way environments are represented in human entorhinal cortex. Given that our daily environments are rarely wide open and are often segmented by barriers (e.g., the buildings of our home city), our findings have implications for applying models of cognitive mapping based on grid-like metrics [8] to naturalistic circumstances.

SUBMITTER: He Q

PROVIDER: S-EPMC7123550 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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Environmental Barriers Disrupt Grid-like Representations in Humans during Navigation.

He Qiliang Q Brown Thackery I TI

Current biology : CB 20190801 16

Environmental barriers fundamentally shape our behavior and conceptualization of space [1-5]. Evidence from rodents suggests that, in contrast to an open-field environment, where grid cells exhibit firing patterns with a 6-fold rotational symmetry [5, 6], barriers within the field abolish the 6-fold symmetry and fragment the grid firing fields into compartmentalized repeating "submaps" [5]. These results suggest that barriers may exert their influence on the cognitive map through organization of ...[more]

PMID: 31378608

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Project description:Grid cells are a special class of spatial cells found in the medial entorhinal cortex (MEC) characterized by their strikingly regular hexagonal firing fields. This spatially periodic firing pattern is originally considered to be independent of the geometric properties of the environment. However, this notion was contested by examining the grid cell periodicity in environments with different polarity (Krupic et al., 2015) and in connected environments (Carpenter et al., 2015). Aforementioned experimental results demonstrated the dependence of grid cell activity on environmental geometry. Analysis of grid cell periodicity on practically infinite variations of environmental geometry imposes a limitation on the experimental study. Hence we analyze the dependence of grid cell periodicity on the environmental geometry purely from a computational point of view. We use a hierarchical oscillatory network model where velocity inputs are presented to a layer of Head Direction cells, outputs of which are projected to a Path Integration layer. The Lateral Anti-Hebbian Network (LAHN) is used to perform feature extraction from the Path Integration neurons thereby producing a spectrum of spatial cell responses. We simulated the model in five types of environmental geometries such as: (1) connected environments, (2) convex shapes, (3) concave shapes, (4) regular polygons with varying number of sides, and (5) transforming environment. Simulation results point to a greater function for grid cells than what was believed hitherto. Grid cells in the model encode not just the local position but also more global information like the shape of the environment. Furthermore, the model is able to capture the invariant attributes of the physical space ingrained in its LAHN layer, thereby revealing its ability to classify an environment using this information. The proposed model is interesting not only because it is able to capture the experimental results but, more importantly, it is able to make many important predictions on the effect of the environmental geometry on the grid cell periodicity and suggesting the possibility of grid cells encoding the invariant properties of an environment.

Dataset Information

Environmental Barriers Disrupt Grid-like Representations in Humans during Navigation.

Publications

Environmental Barriers Disrupt Grid-like Representations in Humans during Navigation.

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