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Across species, how aging leads to progressive spatial memory decline is not fully understood. This study reports dysfunctional spatial coding by aged entorhinal grid cells and networks related to impaired spatial memory and identifies implicated neuronal gene expression changes.

Ketamine’s antidepressant effects can be accompanied by altered spatial cognition. Here, the authors record from thousands of neurons in awake behaving mice to reveal how ketamine disrupts coding in the spatial navigation circuit.

How entorhinal grid cells control hippocampal coding and behavior remains elusive. The authors report that increasing the spatial scale of grid cells expands the scale and reduces the stability of place fields, impairing spatial memory in mice.

Sosa et al. find that hippocampal neural activity in mice encodes both environmental location and experience relative to rewards, spanning distances far from reward, through parallel and flexible population-level codes.

Here, the authors show that mouse medial entorhinal cortex encodes three-dimensional head movement as well as eye position and velocity. These self-motion signals are represented conjunctively in individual neurons alongside body position, running speed, and azimuthal head direction.

Drug-associated contexts are a strong trigger for relapse to substance use. Here, the authors report that a subpopulation of neurons in the hippocampus of mice specifically encode drug-associated contextual information.

Two studies in flies reveal the mechanism by which the brain’s directional system learns to align information about self-orientation with environmental landmarks — a process crucial for accurate navigation.

How the navigational system of the brain constructs spatial maps that require both rapid changes and representational accuracy is explored.

The hippocampus, a structure critical for memory and navigation, contains both place and episodic cell assemblies. Synchronous input from the medial septum is crucial for inducing spatial and temporal neural sequences. These sequences are, in turn, necessary for constructing episodic cells and, in the absence of sensory input, place cells.

Neurons in a brain region called the hippocampus were found to be selectively active when rats are in a specific spatial location during natural navigation. The discovery launched research efforts into how the brain supports spatial memory.

Longitudinal calcium imaging reveals the ability of corner cells to synchronize their activity with the environment, with the results implying the potential of the subiculum to contain the information required to reconstruct spatial environments.

An analysis reveals that fruit-fly neurons orient flies relative to cues in the insects' environment, providing evidence that the fly's brain contains a key component for drawing a cognitive map of the insect's surroundings. See Article p.186

Combining virtual reality and large-scale calcium imaging, the authors demonstrate that hippocampal place cell remapping across contexts can be precisely predicted by the experience of the animal and approximates optimal probabilistic inference.

The ASAP4 family of genetically encoded voltage indicators allows recording of action potentials and subthreshold activity with either one- or two-photon microscopy over extended periods of time.

Munn et al. provide evidence that medial entorhinal speed signals scale to reflect the geometry of the environment, whereas entorhinal head direction signals reflect learned information about the geometric symmetry of the environment.

Using a combination of in vivo recording and theoretical modeling, Campbell et al. develop a framework for understanding the integration of self-motion and landmark cues in entorhinal cortex and demonstrate that these principles extend to behavior.

Pettit, Yuan and Harvey find that hippocampal spatial maps degrade when mice voluntarily disengage from a navigation task, even without changes in sensory or self-motion cues. This finding suggests that internal state could have an active role in supporting navigational coding and, perhaps, spatial memory.

The capacity to navigate to a previously encountered or predicted reward, such as food or safety, is crucial for survival. Here, Sosa and Giocomo examine the neural mechanisms that encode reward location and propose key roles for the hippocampus and the entorhinal cortex in storing and retrieving reward-related information in the brain.

The medial entorhinal cortex contains spatially selective grid cells, whose lattice-like firing patterns are proposed to support path-integration-based navigation. However, direct behavioral evidence has been lacking. Gil et al. disrupt grid cells in a targeted manner, establishing a clear link between grid cell codes and navigation.

Entorhinal cortical grid cells have been suggested to encode an internal map of the environment during spatial navigation. In this Perspective, Rueckemann, Sosa and colleagues propose that grid cells and hippocampal place cells cooperate to provide a topological representation of experience through temporal ordering of events, in both spatial and non-spatial contexts.

In this Perspective, the authors propose that functional insights into generalist cortical computation may reside at the level of population patterns rather than functionally defined cell types. They then review results showing that medial entorhinal cortex (MEC) neurons exhibit substantial heterogeneity, suggesting MEC is a generalist circuit that computes diverse episodic states.

A challenge in translational research is comparing behaviors across species. A new study combines a novel behavioral paradigm in rats and humans with reinforcement learning to infer shared computations for goal-directed navigation.