scholarly journals Grid cells show field-to-field variability and this explains the aperiodic response of inhibitory interneurons

2017 ◽  
Author(s):  
Benjamin Dunn ◽  
Daniel Wennberg ◽  
Ziwei Huang ◽  
Yasser Roudi
Keyword(s):  
Experimental Data ◽  
Firing Rate ◽  
Grid Cell ◽  
Network Models ◽  
Theoretical Models ◽  
Inhibitory Neurons ◽  
Inhibitory Interneurons ◽  
Grid Cells ◽  
External Stimuli ◽  
Individual Grid

AbstractResearch on network mechanisms and coding properties of grid cells assume that the firing rate of a grid cell in each of its fields is the same. Furthermore, proposed network models predict spatial regularities in the firing of inhibitory interneurons that are inconsistent with experimental data. In this paper, by analyzing the response of grid cells recorded from rats during free navigation, we first show that there are strong variations in the mean firing rate of the fields of individual grid cells and thus show that the data is inconsistent with the theoretical models that predict similar peak magnitudes. We then build a two population excitatory-inhibitory network model in which sparse spatially selective input to the excitatory cells, presumed to arise from e.g. salient external stimuli, hippocampus or a combination of both, leads to the variability in the firing field amplitudes of grid cells. We show that, when combined with appropriate connectivity between the excitatory and inhibitory neurons, the variability in the firing field amplitudes of grid cells results in inhibitory neurons that do not exhibit regular spatial firing, consistent with experimental data. Finally, we show that even if the spatial positions of the fields are maintained, variations in the firing rates of the fields of grid cells are enough to cause remapping of hippocampal cells.

scholarly journals Computation by oscillations: Implications of experimental data for theoretical models of grid cells

Hippocampus ◽  
2008 ◽  
Vol 18 (12) ◽  
pp. 1186-1199 ◽  
Author(s):  
Lisa M. Giocomo ◽  
Michael E. Hasselmo
Keyword(s):  
Experimental Data ◽  
Theoretical Models ◽  
Grid Cells

scholarly journals Replay as wavefronts and theta sequences as bump oscillations in a grid cell attractor network

2019 ◽  
Author(s):  
Louis Kang ◽  
Michael R. DeWeese
Keyword(s):  
Slow Wave Sleep ◽  
Cell Formation ◽  
Grid Cell ◽  
External Input ◽  
Inhibitory Interneurons ◽  
Grid Cells ◽  
Attractor Network ◽  
Theta Frequency ◽  
Phase Precession ◽  
Underlying Mechanisms

Grid cells fire in sequences that represent rapid trajectories in space. During locomotion, theta sequences encode sweeps in position starting slightly behind the animal and ending ahead of it. During quiescence and slow wave sleep, bouts of synchronized activity represent long trajectories called replays, which are well-established in place cells and have been recently reported in grid cells. Theta sequences and replay are hypothesized to facilitate many cognitive functions, but their underlying mechanisms are unknown. A leading mechanism proposed for grid cell formation is the continuous attractor network. We demonstrate that this established architecture naturally produces theta sequences and replay as distinct consequences of modulating external input. Driving inhibitory interneurons at the theta frequency causes attractor bumps to oscillate in speed and size, which gives rise to theta sequences and phase precession, respectively. Decreasing input drive to all neurons produces traveling wavefronts of activity that are decoded as replays.

scholarly journals Replay as wavefronts and theta sequences as bump oscillations in a grid cell attractor network

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Louis Kang ◽  
Michael R DeWeese
Keyword(s):  
Slow Wave Sleep ◽  
Cell Formation ◽  
Grid Cell ◽  
External Input ◽  
Inhibitory Interneurons ◽  
Grid Cells ◽  
Attractor Network ◽  
Theta Frequency ◽  
Phase Precession ◽  
Underlying Mechanisms

Grid cells fire in sequences that represent rapid trajectories in space. During locomotion, theta sequences encode sweeps in position starting slightly behind the animal and ending ahead of it. During quiescence and slow wave sleep, bouts of synchronized activity represent long trajectories called replays, which are well-established in place cells and have been recently reported in grid cells. Theta sequences and replay are hypothesized to facilitate many cognitive functions, but their underlying mechanisms are unknown. One mechanism proposed for grid cell formation is the continuous attractor network. We demonstrate that this established architecture naturally produces theta sequences and replay as distinct consequences of modulating external input. Driving inhibitory interneurons at the theta frequency causes attractor bumps to oscillate in speed and size, which gives rise to theta sequences and phase precession, respectively. Decreasing input drive to all neurons produces traveling wavefronts of activity that are decoded as replays.

scholarly journals Perineuronal nets stabilize the grid cell network

2019 ◽  
Author(s):  
Ane Charlotte Christensen ◽  
Kristian Kinden Lensjø ◽  
Mikkel Elle Lepperød ◽  
Svenn-Arne Dragly ◽  
Halvard Sutterud ◽  
...  
Keyword(s):  
Hippocampal Neurons ◽  
Grid Cell ◽  
Inhibitory Neurons ◽  
Perineuronal Nets ◽  
Spatial Representations ◽  
Grid Cells ◽  
Adult Rats ◽  
Cell Network ◽  
Navigation And Spatial Memory ◽  
Cell Modules

AbstractGrid cells are part of a widespread network that supports navigation and spatial memory. Stable grid patterns appear late in development, in concert with extracellular matrix aggregates termed perineuronal nets (PNNs) that condense around inhibitory neurons. To reveal the relationship between stable spatial representations and the presence of PNNs we recorded from populations of neurons in adult rats. We show that removal of PNNs leads to lower inhibitory spiking activity, and reduces grid cells’ ability to create stable representations of a novel environment. Furthermore, in animals with disrupted PNNs, exposure to a novel arena corrupted the spatiotemporal relationships within grid cell modules, and the stored representations of a familiar arena. Finally, we show that PNN removal in entorhinal cortex distorted spatial representations in downstream hippocampal neurons. Together this work suggests that PNNs provide a key stabilizing element for the grid cell network.

scholarly journals Grid cell co-activity patterns during sleep reflect spatial overlap of grid fields during active behaviors

2017 ◽  
Author(s):  
Sean G. Trettel ◽  
John B. Trimper ◽  
Ernie Hwaun ◽  
Ila R. Fiete ◽  
Laura Lee Colgin
Keyword(s):  
Activity Patterns ◽  
Cell Activity ◽  
Grid Cell ◽  
Network Models ◽  
Grid Cells ◽  
Tuning Curves ◽  
Sensory Inputs ◽  
Cell Network ◽  
Spatial Tuning ◽  
Cell Cell

ABSTRACTContinuous attractor network models of grid formation posit that recurrent connectivity between grid cells controls their patterns of co-activation. Grid cells from a common module exhibit stable offsets in their periodic spatial tuning curves across environments, which may reflect recurrent connectivity or correlated sensory inputs. Here we explore whether cell-cell relationships predicted by attractor models persist during sleep states in which spatially informative sensory inputs are absent. We recorded ensembles of grid cells in superficial layers of medial entorhinal cortex during active exploratory behaviors and overnight sleep. Per pair and collectively, we found preserved patterns of spike-time correlations across waking, REM, and non-REM sleep, which reflected the spatial tuning offsets between these cells during active exploration. The preservation of cell-cell relationships across states was not explained by theta oscillations or CA1 activity. These results suggest that recurrent connectivity within the grid cell network drives grid cell activity across behavioral states.

scholarly journals Differential effects of amplitude-modulated transcranial focused ultrasound on excitatory and inhibitory neurons

2020 ◽  
Author(s):  
Duc T. Nguyen ◽  
Destiny Berisha ◽  
Elisa Konofagou ◽  
Jacek P. Dmochowski
Keyword(s):  
Firing Rate ◽  
Focused Ultrasound ◽  
Multiple Scales ◽  
Brain Activity ◽  
Field Potential ◽  
Pyramidal Cells ◽  
Inhibitory Neurons ◽  
Specific Cell ◽  
Inhibitory Interneurons ◽  
Transcranial Focused Ultrasound

AbstractAlthough stimulation with ultrasound has been shown to modulate brain activity at multiple scales, it remains unclear whether transcranial focused ultrasound stimulation (tFUS) exerts its influence on specific cell types. Here we propose a novel form of tFUS where a continuous waveform is amplitude modulated (AM) at a slow rate (i.e., 40 Hz) targeting the temporal range of electrophysiological activity: AM-tFUS. We stimulated the rat hippocampus while recording multi-unit activity (MUA) followed by classification of spike waveforms into putative excitatory pyramidal cells and inhibitory interneurons. At low acoustic intensity, AM-tFUS selectively reduced firing rates of inhibitory interneurons. On the other hand, higher intensity AM-tFUS increased firing of putative excitatory neurons with no effect on inhibitory firing. Interestingly, firing rate was unchanged during AM-tFUS at intermediate intensity. Consistent with the observed changes in firing rate, power in the theta band (3-10 Hz) of the local field potential (LFP) decreased at low-intensity, was unchanged at intermediate intensity, and increased at higher intensity. Temperature increases at the AM-tFUS target were limited to 0.2°C. Our findings indicate that inhibitory interneurons exhibit greater sensitivity to ultrasound, and that cell-type specific neuromodulation may be achieved by calibrating the intensity of AM-tFUS.

scholarly journals Visual landmarks sharpen grid cell metric and confer context specificity to neurons of the medial entorhinal cortex

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
José Antonio Pérez-Escobar ◽  
Olga Kornienko ◽  
Patrick Latuske ◽  
Laura Kohler ◽  
Kevin Allen
Keyword(s):  
Firing Rate ◽  
Entorhinal Cortex ◽  
Visual Information ◽  
Grid Cell ◽  
Grid Cells ◽  
Contextual Cues ◽  
Context Specificity ◽  
Visual Landmarks ◽  
Medial Entorhinal Cortex ◽  
Geometrical Properties

Neurons of the medial entorhinal cortex (MEC) provide spatial representations critical for navigation. In this network, the periodic firing fields of grid cells act as a metric element for position. The location of the grid firing fields depends on interactions between self-motion information, geometrical properties of the environment and nonmetric contextual cues. Here, we test whether visual information, including nonmetric contextual cues, also regulates the firing rate of MEC neurons. Removal of visual landmarks caused a profound impairment in grid cell periodicity. Moreover, the speed code of MEC neurons changed in darkness and the activity of border cells became less confined to environmental boundaries. Half of the MEC neurons changed their firing rate in darkness. Manipulations of nonmetric visual cues that left the boundaries of a 1D environment in place caused rate changes in grid cells. These findings reveal context specificity in the rate code of MEC neurons.

scholarly journals Burst activity plays no role for the field-to-field variability and rate remapping of grid cells

2020 ◽  
Author(s):  
Michaela Poth ◽  
Andreas V.M. Herz
Keyword(s):  
Firing Rate ◽  
Time Scales ◽  
Neural Coding ◽  
Hexagonal Lattice ◽  
Grid Cell ◽  
Grid Cells ◽  
Firing Patterns ◽  
Firing Rates ◽  
Coding Schemes ◽  
Short Time

AbstractGrid cells in rodent medial entorhinal cortex are thought to play a key role for spatial navigation. When the animal is freely moving in an open arena the firing fields of each grid cell tend to form a hexagonal lattice spanning the environment. Firing rates vary from field to field and change under contextual modifications, whereas the field locations do not shift under such “rate remapping”. The observed differences in firing rate could reflect overall activity changes or changes in the detailed spike-train statistics. As these two alternatives imply distinct neural coding schemes, we investigated whether temporal firing patterns vary from field to field and whether they change under rate remapping. Focusing on short time scales, we found that the proportion of bursts compared to all discharge events is similar in all firing fields of a given grid cell and does not change under rate remapping. Mean firing rates with and without bursts are proportional for each cell. However, this ratio varies across cells. Additionally, we looked at how rate remapping relates to entorhinal theta-frequency oscillations. Theta-phase coding was preserved despite firing-rate changes from rate remapping but we did not observe differences between the first and second half of the theta cycle, as had been reported for CA1. Our results indicate that both, the heterogeneity between firing fields and rate remapping, are not due to altered firing patterns on short time scales but reflect location-specific changes at the firing-rate level.

TEMPERATURE DEPENDENCE BEHAVIOR OF ELECTRICAL RESISTIVITY IN NOBLE METALS AT LOW TEMPERATURES

2014 ◽  
Vol 5 (3) ◽  
pp. 982-992 ◽  
Author(s):  
M AL-Jalali
Keyword(s):  
Experimental Data ◽  
Electrical Resistivity ◽  
Temperature Dependence ◽  
Concentration Dependence ◽  
Low Temperatures ◽  
Noble Metals ◽  
Phonon Scattering ◽  
Theoretical Models ◽  
Residual Resistivity ◽  
Electron Phonon Scattering

Resistivity temperature – dependence and residual resistivity concentration-dependence in pure noble metals(Cu, Ag, Au) have been studied at low temperatures. Dominations of electron – dislocation and impurity, electron-electron, and electron-phonon scattering were analyzed, contribution of these mechanisms to resistivity were discussed, taking into consideration existing theoretical models and available experimental data, where some new results and ideas were investigated.

Sign in / Sign up

Export Citation Format

Share Document