Muscarinic Induction of Synchronous Population Activity in the Entorhinal Cortex

Learning-related changes in brain activity are thought to underlie adaptive behaviors. For instance, the learning of a reward site by rodents requires the development of an over-representation of that location in the hippocampus. However, how this learning-related change occurs remains unknown. Here we recorded hippocampal CA1 population activity as mice learned a reward location on a linear treadmill. Physiological and pharmacological evidence suggests that the adaptive over-representation required behavioral timescale synaptic plasticity (BTSP). BTSP is known to be driven by dendritic voltage signals that we hypothesized were initiated by input from entorhinal cortex layer 3 (EC3). Accordingly, the CA1 over-representation was largely removed by optogenetic inhibition of EC3 activity. Recordings from EC3 neurons revealed an activity pattern that could provide an instructive signal directing BTSP to generate the over-representation. Consistent with this function, exposure to a second environment possessing a prominent reward-predictive cue resulted in both EC3 activity and CA1 place field density that were more elevated at the cue than the reward. These data indicate that learning-related changes in the hippocampus are produced by synaptic plasticity directed by an instructive signal from the EC3 that appears to be specifically adapted to the behaviorally relevant features of the environment.

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Effect of reward on electrophysiological signatures of grid cell population activity in human spatial navigation

Scientific Reports ◽

10.1038/s41598-021-03124-y ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Wenjing Wang ◽

Wenxu Wang

Keyword(s):

Cell Population ◽

Entorhinal Cortex ◽

Grid Cell ◽

Grid Cells ◽

Grid Pattern ◽

Population Activity ◽

Spatial Measures ◽

Moving Direction ◽

Patients With Epilepsy ◽

Reward Information

AbstractThe regular equilateral triangular periodic firing pattern of grid cells in the entorhinal cortex is considered a regular metric for the spatial world, and the grid-like representation correlates with hexadirectional modulation of theta (4–8 Hz) power in the entorhinal cortex relative to the moving direction. However, researchers have not clearly determined whether grid cells provide only simple spatial measures in human behavior-related navigation strategies or include other factors such as goal rewards to encode information in multiple patterns. By analysing the hexadirectional modulation of EEG signals in the theta band in the entorhinal cortex of patients with epilepsy performing spatial target navigation tasks, we found that this modulation presents a grid pattern that carries target-related reward information. This grid-like representation is influenced by explicit goals and is related to the local characteristics of the environment. This study provides evidence that human grid cell population activity is influenced by reward information at the level of neural oscillations.

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Robust and Efficient Coding with Grid Cells

10.1101/107060 ◽

2017 ◽

Author(s):

Lajos Vágó ◽

Balázs B Ujfalussy

Keyword(s):

Entorhinal Cortex ◽

Upper Bound ◽

Grid Cell ◽

Parameter Tuning ◽

Grid Cells ◽

Theoretic Analysis ◽

Population Activity ◽

Efficient Coding ◽

Neuronal Code ◽

Random Scale

AbstractThe neuronal code arising from the coordinated population activity of grid cells in the rodent entorhinal cortex can uniquely represent space across large distances but the precise conditions for efficient coding are unknown. Here we present a number-theoretic analysis of grid coding and derive an upper bound on the distance that a population of grid cells can represent without error. We show that in the absence of neuronal noise, the capacity of the system would be extremely sensitive to the choice of the grid periods. However, when the accuracy of the representation is limited by neuronal noise, the capacity becomes gradually more robust against the choice of grid scales as the number of modules increases and remains near optimal even for random scale choices. Our study reveals that robust and efficient coding can be achieved without parameter tuning in the case of grid cell representation.

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Dentate gyrus population activity during immobility supports formation of precise memories

10.1101/2020.03.05.978320 ◽

2020 ◽

Author(s):

Martin Pofahl ◽

Negar Nikbakht ◽

André N. Haubrich ◽

Theresa Nguyen ◽

Nicola Masala ◽

...

Keyword(s):

Dentate Gyrus ◽

Entorhinal Cortex ◽

Granule Cells ◽

Activity Patterns ◽

Cell Activity ◽

Sensory Information ◽

Population Activity ◽

Hippocampus Proper ◽

Spatial Memories

AbstractThe hippocampal dentate gyrus is an important relay conveying sensory information from the entorhinal cortex to the hippocampus proper. During exploration, the dentate gyrus has been proposed to act as a pattern separator. However, the dentate gyrus also shows structured activity during immobility and sleep. The properties of these activity patterns at cellular resolution, and their role in hippocampal-dependent memory processes have remained unclear. Using dual-color in-vivo two-photon Ca2+ imaging, we show that in immobile mice dentate granule cells generate sparse, synchronized activity patterns associated with entorhinal cortex activation. These population events are structured and modified by changes in the environment; and they incorporate place- and speed cells. Importantly, they recapitulate population patterns evoked during self-motion. Using optogenetic inhibition during immobility, we show that granule cell activity during immobility is required to form dentate gyrus-dependent spatial memories. These data suggest that memory formation is supported by dentate gyrus replay of population codes of the current environment.

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