scholarly journals Spatial Theta Cells in Competitive Burst Synchronization Networks: Reference Frames from Phase Codes

2017 ◽  
Author(s):  
Joseph D. Monaco ◽  
Hugh T. Blair ◽  
Kechen Zhang
Keyword(s):  
Reference Frames ◽  
Hippocampal Formation ◽  
Temporal Coding ◽  
Reference Points ◽  
Temporal Phase ◽  
Independent Mechanism ◽  
Single Unit Recordings ◽  
Burst Synchronization ◽  
Low Dimensional ◽  
Self Motion

AbstractSpatial cells of the hippocampal formation are embedded in networks of theta cells. The septal theta rhythm (6–10 Hz) organizes the spatial activity of place and grid cells in time, but it remains unclear how spatial reference points organize the temporal activity of theta cells in space. We study spatial theta cells in simulations and single-unit recordings from exploring rats to ask whether temporal phase codes may anchor spatial representations to the outside world. We theorize that an experience-independent mechanism for temporal coding may combine with burst synchronization to continuously calibrate self-motion to allocentric reference frames. Subcortical recordings revealed spatial theta cells with strong rate-phase correlations related to distinct theta phases. Simulations of bursting neurons and networks explained that relationship and, with competitive learning, demonstrated flexible spatial synchronization patterns when driven by low-dimensional spatial components from the recording data. Thus temporal coding synchrony may reconcile extrinsic and intrinsic neural codes.

scholarly journals Egocentric and Allocentric Spatial Memory in Mild Cognitive Impairment with Real-World and Virtual Navigation Tasks: A Systematic Review

2021 ◽  
Vol 79 (1) ◽  
pp. 95-116
Author(s):  
Cosimo Tuena ◽  
Valentina Mancuso ◽  
Chiara Stramba-Badiale ◽  
Elisa Pedroli ◽  
Marco Stramba-Badiale ◽  
...  
Keyword(s):  
Systematic Review ◽  
Cognitive Impairment ◽  
Mild Cognitive Impairment ◽  
Spatial Memory ◽  
Real World ◽  
Reference Frames ◽  
Spatial Navigation ◽  
Experimental Studies ◽  
Motion Cues ◽  
Self Motion

Background: Spatial navigation is the ability to estimate one’s position on the basis of environmental and self-motion cues. Spatial memory is the cognitive substrate underlying navigation and relies on two different reference frames: egocentric and allocentric. These spatial frames are prone to decline with aging and impairment is even more pronounced in Alzheimer’s disease (AD) or in mild cognitive impairment (MCI). Objective: To conduct a systematic review of experimental studies investigating which MCI population and tasks are used to evaluate spatial memory and how allocentric and egocentric deficits are impaired in MCI after navigation. Methods: PRISMA and PICO guidelines were applied to carry out the systematic search. Down and Black checklist was used to assess methodological quality. Results: Our results showed that amnestic MCI and AD pathology are the most investigated typologies; both egocentric and allocentric memory are impaired in MCI individuals, and MCI due to AD biomarkers has specific encoding and retrieval impairments; secondly, spatial navigation is principally investigated with the hidden goal task (virtual and real-world version), and among studies involving virtual reality, the privileged setting consists of non-immersive technology; thirdly, despite subtle differences, real-world and virtual versions showed good overlap for the assessment of MCI spatial memory. Conclusion: Considering that MCI is a subclinical entity with potential risk for conversion to dementia, investigating spatial memory deficits with navigation tasks might be crucial to make accurate diagnosis and rehabilitation.

scholarly journals Functional correlates of the lateral and medial entorhinal cortex: objects, path integration and local–global reference frames

2014 ◽  
Vol 369 (1635) ◽  
pp. 20130369 ◽  
Author(s):  
James J. Knierim ◽  
Joshua P. Neunuebel ◽  
Sachin S. Deshmukh
Keyword(s):  
Entorhinal Cortex ◽  
Path Integration ◽  
Sensory Input ◽  
Reference Frames ◽  
External Input ◽  
Frame Of Reference ◽  
Medial Entorhinal Cortex ◽  
Motion Cues ◽  
Cortical Input ◽  
Self Motion

The hippocampus receives its major cortical input from the medial entorhinal cortex (MEC) and the lateral entorhinal cortex (LEC). It is commonly believed that the MEC provides spatial input to the hippocampus, whereas the LEC provides non-spatial input. We review new data which suggest that this simple dichotomy between ‘where’ versus ‘what’ needs revision. We propose a refinement of this model, which is more complex than the simple spatial–non-spatial dichotomy. MEC is proposed to be involved in path integration computations based on a global frame of reference, primarily using internally generated, self-motion cues and external input about environmental boundaries and scenes; it provides the hippocampus with a coordinate system that underlies the spatial context of an experience. LEC is proposed to process information about individual items and locations based on a local frame of reference, primarily using external sensory input; it provides the hippocampus with information about the content of an experience.

scholarly journals Egocentric Asymmetric Coding in Sensory Cortical Border Cells

2021 ◽  
Author(s):  
Xiaoyang Long ◽  
Bin Deng ◽  
Jing Cai ◽  
Zhe Sage Chen ◽  
Sheng-Jia Zhang
Keyword(s):  
Reference Frames ◽  
Hippocampal Formation ◽  
Spatial Navigation ◽  
List Type ◽  
Border Cells ◽  
Spatial Coding ◽  
Egocentric Reference Frame ◽  
Border Cell ◽  
Sensory Cortices ◽  
Representations Of Space

ABSTRACTBoth egocentric and allocentric representations of space are essential to spatial navigation. Although some studies of egocentric coding have been conducted within and around the hippocampal formation, externally anchored egocentric spatial representations have not yet been fully explored. Here we record and identify two subtypes of border cell in the rat primary somatosensory cortex (S1) and secondary visual cortex (V2). Subpopulations of S1 and V2 border cells exhibit rotation-selective asymmetric firing fields in an either clockwise (CW) or counterclockwise (CCW) manner. CW- and CCW-border cells increase their firing rates when animals move unidirectionally along environmental border(s). We demonstrate that both CW- and CCW-border cells fire in an egocentric reference frame relative to environmental borders, maintain preferred directional tunings in rotated, stretched, dark as well as novel arenas, and switch their directional firings in the presence of multi-layer concentric enclosures. These findings may provide rotation-selective egocentric reference frames within a larger spatial navigation system, and point to a common computational principle of spatial coding shared by multiple sensory cortical areas.HighlightsEgocentric border cells are present in rat S1 and V2Subtypes of border cells display egocentric asymmetric codingEgocentric and allocentric streams coexist in sensory corticesRotation-selective asymmetric firing is robust with environmental manipulations

scholarly journals Boundary coding in the rat subiculum

2014 ◽  
Vol 369 (1635) ◽  
pp. 20120514 ◽  
Author(s):  
Sarah Stewart ◽  
Ali Jeewajee ◽  
Thomas J. Wills ◽  
Neil Burgess ◽  
Colin Lever
Keyword(s):  
Hippocampal Formation ◽  
External Environment ◽  
Mapping Function ◽  
The Other ◽  
Spatial Mapping ◽  
Testing Environment ◽  
New Class ◽  
Boundary Vector ◽  
Temporal Properties ◽  
Self Motion

The spatial mapping function of the hippocampal formation is likely derived from two sets of information: one based on the external environment and the other based on self-motion. Here, we further characterize ‘boundary vector cells’ (BVCs) in the rat subiculum, which code space relative to one type of cue in the external environment: boundaries. We find that the majority of cells with fields near the perimeter of a walled environment exhibit an additional firing field when an upright barrier is inserted into the walled environment in a manner predicted by the BVC model. We use this property of field repetition as a heuristic measure to define BVCs, and characterize their spatial and temporal properties. In further tests, we find that subicular BVCs typically treat drop edges similarly to walls, including exhibiting field repetition when additional drop-type boundaries are added to the testing environment. In other words, BVCs treat both kinds of edge as environmental boundaries, despite their dissimilar sensory properties. Finally, we also report the existence of ‘boundary-off cells’, a new class of boundary-coding cells. These cells fire everywhere except where a given BVC might fire.

scholarly journals Two-sample statistics based on anisotropic kernels

2019 ◽  
Vol 9 (3) ◽  
pp. 677-719 ◽  
Author(s):  
Xiuyuan Cheng ◽  
Alexander Cloninger ◽  
Ronald R Coifman
Keyword(s):  
Reproducing Kernel ◽  
Reproducing Kernel Hilbert Space ◽  
Reference Points ◽  
Finite Sample ◽  
Maximum Mean Discrepancy ◽  
Data Points ◽  
Consistency Of The Test ◽  
Low Dimensional ◽  
Anisotropic Kernel ◽  
Anisotropic Kernels

Abstract The paper introduces a new kernel-based Maximum Mean Discrepancy (MMD) statistic for measuring the distance between two distributions given finitely many multivariate samples. When the distributions are locally low-dimensional, the proposed test can be made more powerful to distinguish certain alternatives by incorporating local covariance matrices and constructing an anisotropic kernel. The kernel matrix is asymmetric; it computes the affinity between $n$ data points and a set of $n_R$ reference points, where $n_R$ can be drastically smaller than $n$. While the proposed statistic can be viewed as a special class of Reproducing Kernel Hilbert Space MMD, the consistency of the test is proved, under mild assumptions of the kernel, as long as $\|p-q\| \sqrt{n} \to \infty $, and a finite-sample lower bound of the testing power is obtained. Applications to flow cytometry and diffusion MRI datasets are demonstrated, which motivate the proposed approach to compare distributions.

scholarly journals Adjacent visual representations of self-motion in different reference frames

2011 ◽  
Vol 108 (28) ◽  
pp. 11668-11673 ◽  
Author(s):  
D. M. Arnoldussen ◽  
J. Goossens ◽  
A. V. van den Berg
Keyword(s):  
Reference Frames ◽  
Visual Representations ◽  
Self Motion

scholarly journals VLBI measurement of the vector baseline between geodetic antennas at Kokee Park Geophysical Observatory, Hawaii

2021 ◽  
Vol 95 (6) ◽  
Author(s):  
A. E. Niell ◽  
J. P. Barrett ◽  
R. J. Cappallo ◽  
B. E. Corey ◽  
P. Elosegui ◽  
...  
Keyword(s):  
Reference Frames ◽  
Geodetic Survey ◽  
Terrestrial Reference Frame ◽  
Reference Points ◽  
Reference Temperature ◽  
National Geodetic Survey ◽  
Geophysical Observatory ◽  
Common Reference ◽  
Long Baseline ◽  
Gravitational Deformation

AbstractWe measured the components of the 31-m-long vector between the two very-long-baseline interferometry (VLBI) antennas at the Kokee Park Geophysical Observatory (KPGO), Hawaii, with approximately 1 mm precision using phase delay observables from dedicated VLBI observations in 2016 and 2018. The two KPGO antennas are the 20 m legacy VLBI antenna and the 12 m VLBI Global Observing System (VGOS) antenna. Independent estimates of the vector between the two antennas were obtained by the National Geodetic Survey (NGS) using standard optical surveys in 2015 and 2018. The uncertainties of the latter survey were 0.3 and 0.7 mm in the horizontal and vertical components of the baseline, respectively. We applied corrections to the measured positions for the varying thermal deformation of the antennas on the different days of the VLBI and survey measurements, which can amount to 1 mm, bringing all results to a common reference temperature. The difference between the VLBI and survey results are 0.2 ± 0.4 mm, −1.3 ± 0.4 mm, and 0.8 ± 0.8 mm in the East, North, and Up topocentric components, respectively. We also estimate that the Up component of the baseline may suffer from systematic errors due to gravitational deformation and uncalibrated instrumental delay variations at the 20 m antenna that may reach ± 10 and −2 mm, respectively, resulting in an accuracy uncertainty on the order of 10 mm for the relative heights of the antennas. Furthermore, possible tilting of the 12 m antenna increases the uncertainties in the differences in the horizontal components to 1.0 mm. These results bring into focus the importance of (1) correcting to a common reference temperature the measurements of the reference points of all geodetic instruments within a site, (2) obtaining measurements of the gravitational deformation of all antennas, and (3) monitoring local motions of the geodetic instruments. These results have significant implications for the accuracy of global reference frames that require accurate local ties between geodetic instruments, such as the International Terrestrial Reference Frame (ITRF).

scholarly journals Neural dynamics indicate parallel integration of environmental and self-motion information by place and grid cells

2019 ◽  
Author(s):  
Dmitri Laptev ◽  
Neil Burgess
Keyword(s):  
Path Integration ◽  
Temporal Dynamics ◽  
Hippocampal Formation ◽  
Place Cell ◽  
Place Cells ◽  
Motion Information ◽  
Grid Cells ◽  
Attractor Network ◽  
Cell Firing ◽  
Self Motion

AbstractPlace cells and grid cells in the hippocampal formation are thought to integrate sensory and self-motion information into a representation of estimated spatial location, but the precise mechanism is unknown. We simulated a parallel attractor system in which place cells form an attractor network driven by environmental inputs and grid cells form an attractor network performing path integration driven by self-motion, with inter-connections between them allowing both types of input to influence firing in both ensembles. We show that such a system is needed to explain the spatial patterns and temporal dynamics of place cell firing when rats run on a linear track in which the familiar correspondence between environmental and self-motion inputs is changed (Gothard et al., 1996b; Redish et al., 2000). In contrast, the alternative architecture of a single recurrent network of place cells (performing path integration and receiving environmental inputs) cannot reproduce the place cell firing dynamics. These results support the hypothesis that grid and place cells provide two different but complementary attractor representations (based on self-motion and environmental sensory inputs respectively). Our results also indicate the specific neural mechanism and main predictors of hippocampal map realignment and make predictions for future studies.

scholarly journals Velocity coupling of grid cell modules enables stable embedding of a low dimensional variable in a high dimensional neural attractor

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Noga Mosheiff ◽  
Yoram Burak
Keyword(s):  
Grid Cell ◽  
Large Capacity ◽  
Variable Position ◽  
Higher Dimensional ◽  
Neural Populations ◽  
Cell Modules ◽  
Abrupt Shifts ◽  
Low Dimensional ◽  
Dimensional Variable ◽  
Self Motion

Grid cells in the medial entorhinal cortex (MEC) encode position using a distributed representation across multiple neural populations (modules), each possessing a distinct spatial scale. The modular structure of the representation confers the grid cell neural code with large capacity. Yet, the modularity poses significant challenges for the neural circuitry that maintains the representation, and updates it based on self motion. Small incompatible drifts in different modules, driven by noise, can rapidly lead to large, abrupt shifts in the represented position, resulting in catastrophic readout errors. Here, we propose a theoretical model of coupled modules. The coupling suppresses incompatible drifts, allowing for a stable embedding of a two-dimensional variable (position) in a higher dimensional neural attractor, while preserving the large capacity. We propose that coupling of this type may be implemented by recurrent synaptic connectivity within the MEC with a relatively simple and biologically plausible structure.

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