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Estimating location without external cues.

Cheung A - PLoS Comput. Biol. (2014)

Bottom Line: Surprisingly, localization does not require the sensing of any external cue, including the boundary.Optimal localization performance was found to depend on arena shape, arena size, local and global rotational asymmetry, and the structure of the path taken during localization.Based on these results, experiments are suggested to identify if and where information fusion occurs in the mammalian spatial memory system.

View Article: PubMed Central - PubMed

Affiliation: The University of Queensland, Queensland Brain Institute, Brisbane, Queensland, Australia.

ABSTRACT
The ability to determine one's location is fundamental to spatial navigation. Here, it is shown that localization is theoretically possible without the use of external cues, and without knowledge of initial position or orientation. With only error-prone self-motion estimates as input, a fully disoriented agent can, in principle, determine its location in familiar spaces with 1-fold rotational symmetry. Surprisingly, localization does not require the sensing of any external cue, including the boundary. The combination of self-motion estimates and an internal map of the arena provide enough information for localization. This stands in conflict with the supposition that 2D arenas are analogous to open fields. Using a rodent error model, it is shown that the localization performance which can be achieved is enough to initiate and maintain stable firing patterns like those of grid cells, starting from full disorientation. Successful localization was achieved when the rotational asymmetry was due to the external boundary, an interior barrier or a void space within an arena. Optimal localization performance was found to depend on arena shape, arena size, local and global rotational asymmetry, and the structure of the path taken during localization. Since allothetic cues including visual and boundary contact cues were not present, localization necessarily relied on the fusion of idiothetic self-motion cues and memory of the boundary. Implications for spatial navigation mechanisms are discussed, including possible relationships with place field overdispersion and hippocampal reverse replay. Based on these results, experiments are suggested to identify if and where information fusion occurs in the mammalian spatial memory system.

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Successful idiothetic localization in familiar arenas.(A) Uncertainty (blue particle cloud) either oriented or disoriented initially, showing the estimated pose (cyan arrow) was close to the true pose (red arrow) after 90 seconds. For clarity, only the position of each particle's pose is shown. See also Video S1. (B)  at 48 minutes, , was above chance (0.5) either oriented or disoriented initially (Mann-Whitney U-test, p = 4.3×10−164 and p = 7.5×10−161, respectively). In both cases, θ was non-randomly distributed (Rayleigh test, p<10−256) and centred on the true direction (circular m test, p = 0.80 and p = 0.84, respectively) following 48 minutes.  (solid lines) and V(θ) (dotted lines) both showed incomplete convergence at 48 minutes (, Wilcoxon test, p = 2.6×10−5; κ-test, p<10−16). Ip kinetics also differed (disoriented, t90 = 2:18; oriented, t90 = 4:32). (C) Simulated grid cell spikes during idiothetic localization in 4 arenas with 1-fold rotational symmetry, initially disoriented (rows 2–5), and initially oriented (row 1). Autocorrelograms of the normalized firing fields from 46–48 minutes are included (right column). See also Table S1. (D) Median Ip and V(θ) functions (left), and Ip(48) distributions (right) are shown for the four arenas in (C) when initially disoriented.
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pcbi-1003927-g002: Successful idiothetic localization in familiar arenas.(A) Uncertainty (blue particle cloud) either oriented or disoriented initially, showing the estimated pose (cyan arrow) was close to the true pose (red arrow) after 90 seconds. For clarity, only the position of each particle's pose is shown. See also Video S1. (B) at 48 minutes, , was above chance (0.5) either oriented or disoriented initially (Mann-Whitney U-test, p = 4.3×10−164 and p = 7.5×10−161, respectively). In both cases, θ was non-randomly distributed (Rayleigh test, p<10−256) and centred on the true direction (circular m test, p = 0.80 and p = 0.84, respectively) following 48 minutes. (solid lines) and V(θ) (dotted lines) both showed incomplete convergence at 48 minutes (, Wilcoxon test, p = 2.6×10−5; κ-test, p<10−16). Ip kinetics also differed (disoriented, t90 = 2:18; oriented, t90 = 4:32). (C) Simulated grid cell spikes during idiothetic localization in 4 arenas with 1-fold rotational symmetry, initially disoriented (rows 2–5), and initially oriented (row 1). Autocorrelograms of the normalized firing fields from 46–48 minutes are included (right column). See also Table S1. (D) Median Ip and V(θ) functions (left), and Ip(48) distributions (right) are shown for the four arenas in (C) when initially disoriented.

Mentions: Figure 2A shows snapshots of the positional uncertainty distribution along random trajectories, combining idiothetic self-motion cues with arena boundary memory. Starting either oriented or disoriented, the true pose remained close to the estimated pose. remained above 0.5 using idiothetic cues (Fig. 2B) demonstrating localization success. Similarly, the directional component of the pose estimate, θ, was centred on the true direction. Not surprisingly, initial orientation improved position estimation but its effect on Ip was no longer detectable at 96 minutes (Wilcoxon test, p = 0.49). Likewise, V(θ) remained consistently higher when initially disoriented (Fig. 1B, dotted lines), but the effect persisted beyond 192 minutes (κ-test, p = 6.0×10−4). Lastly, 90% of changes in occurred within the first 5 minutes. Together, these results show that idiothetic localization was achieved rapidly even when initially disoriented.


Estimating location without external cues.

Cheung A - PLoS Comput. Biol. (2014)

Successful idiothetic localization in familiar arenas.(A) Uncertainty (blue particle cloud) either oriented or disoriented initially, showing the estimated pose (cyan arrow) was close to the true pose (red arrow) after 90 seconds. For clarity, only the position of each particle's pose is shown. See also Video S1. (B)  at 48 minutes, , was above chance (0.5) either oriented or disoriented initially (Mann-Whitney U-test, p = 4.3×10−164 and p = 7.5×10−161, respectively). In both cases, θ was non-randomly distributed (Rayleigh test, p<10−256) and centred on the true direction (circular m test, p = 0.80 and p = 0.84, respectively) following 48 minutes.  (solid lines) and V(θ) (dotted lines) both showed incomplete convergence at 48 minutes (, Wilcoxon test, p = 2.6×10−5; κ-test, p<10−16). Ip kinetics also differed (disoriented, t90 = 2:18; oriented, t90 = 4:32). (C) Simulated grid cell spikes during idiothetic localization in 4 arenas with 1-fold rotational symmetry, initially disoriented (rows 2–5), and initially oriented (row 1). Autocorrelograms of the normalized firing fields from 46–48 minutes are included (right column). See also Table S1. (D) Median Ip and V(θ) functions (left), and Ip(48) distributions (right) are shown for the four arenas in (C) when initially disoriented.
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Related In: Results  -  Collection

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pcbi-1003927-g002: Successful idiothetic localization in familiar arenas.(A) Uncertainty (blue particle cloud) either oriented or disoriented initially, showing the estimated pose (cyan arrow) was close to the true pose (red arrow) after 90 seconds. For clarity, only the position of each particle's pose is shown. See also Video S1. (B) at 48 minutes, , was above chance (0.5) either oriented or disoriented initially (Mann-Whitney U-test, p = 4.3×10−164 and p = 7.5×10−161, respectively). In both cases, θ was non-randomly distributed (Rayleigh test, p<10−256) and centred on the true direction (circular m test, p = 0.80 and p = 0.84, respectively) following 48 minutes. (solid lines) and V(θ) (dotted lines) both showed incomplete convergence at 48 minutes (, Wilcoxon test, p = 2.6×10−5; κ-test, p<10−16). Ip kinetics also differed (disoriented, t90 = 2:18; oriented, t90 = 4:32). (C) Simulated grid cell spikes during idiothetic localization in 4 arenas with 1-fold rotational symmetry, initially disoriented (rows 2–5), and initially oriented (row 1). Autocorrelograms of the normalized firing fields from 46–48 minutes are included (right column). See also Table S1. (D) Median Ip and V(θ) functions (left), and Ip(48) distributions (right) are shown for the four arenas in (C) when initially disoriented.
Mentions: Figure 2A shows snapshots of the positional uncertainty distribution along random trajectories, combining idiothetic self-motion cues with arena boundary memory. Starting either oriented or disoriented, the true pose remained close to the estimated pose. remained above 0.5 using idiothetic cues (Fig. 2B) demonstrating localization success. Similarly, the directional component of the pose estimate, θ, was centred on the true direction. Not surprisingly, initial orientation improved position estimation but its effect on Ip was no longer detectable at 96 minutes (Wilcoxon test, p = 0.49). Likewise, V(θ) remained consistently higher when initially disoriented (Fig. 1B, dotted lines), but the effect persisted beyond 192 minutes (κ-test, p = 6.0×10−4). Lastly, 90% of changes in occurred within the first 5 minutes. Together, these results show that idiothetic localization was achieved rapidly even when initially disoriented.

Bottom Line: Surprisingly, localization does not require the sensing of any external cue, including the boundary.Optimal localization performance was found to depend on arena shape, arena size, local and global rotational asymmetry, and the structure of the path taken during localization.Based on these results, experiments are suggested to identify if and where information fusion occurs in the mammalian spatial memory system.

View Article: PubMed Central - PubMed

Affiliation: The University of Queensland, Queensland Brain Institute, Brisbane, Queensland, Australia.

ABSTRACT
The ability to determine one's location is fundamental to spatial navigation. Here, it is shown that localization is theoretically possible without the use of external cues, and without knowledge of initial position or orientation. With only error-prone self-motion estimates as input, a fully disoriented agent can, in principle, determine its location in familiar spaces with 1-fold rotational symmetry. Surprisingly, localization does not require the sensing of any external cue, including the boundary. The combination of self-motion estimates and an internal map of the arena provide enough information for localization. This stands in conflict with the supposition that 2D arenas are analogous to open fields. Using a rodent error model, it is shown that the localization performance which can be achieved is enough to initiate and maintain stable firing patterns like those of grid cells, starting from full disorientation. Successful localization was achieved when the rotational asymmetry was due to the external boundary, an interior barrier or a void space within an arena. Optimal localization performance was found to depend on arena shape, arena size, local and global rotational asymmetry, and the structure of the path taken during localization. Since allothetic cues including visual and boundary contact cues were not present, localization necessarily relied on the fusion of idiothetic self-motion cues and memory of the boundary. Implications for spatial navigation mechanisms are discussed, including possible relationships with place field overdispersion and hippocampal reverse replay. Based on these results, experiments are suggested to identify if and where information fusion occurs in the mammalian spatial memory system.

Show MeSH
Related in: MedlinePlus