Sociology

Neuroscience

Cognitive map

Organic chemistry

Calcium imaging

Population

Manifold (fluid mechanics)

ENCODE

Biology

Politics

Gene

Embodied cognition

Curse of dimensionality

Hippocampal formation

Demography

Encoding (memory)

Engineering

Cognition

Political science

Artificial intelligence

Management

Psychology

Economics

Somatosensory system

Chemistry

Representation (politics)

Functional magnetic resonance imaging

Spatial cognition

Hippocampus

Computer science

Task (project management)

Calcium

Biochemistry

Mechanical engineering

Nature

Hippocampal neurons encode physical variables1–7 such as space1 or auditory frequency6 in cognitive maps8. In addition, functional magnetic resonance imaging studies in humans have shown that the hippocampus can also encode more abstract, learned variables9–11. However, their integration into existing neural representations of physical variables12,13 is unknown. Here, using two-photon calcium imaging, we show that individual neurons in the dorsal hippocampus jointly encode accumulated evidence with spatial position in mice performing a decision-making task in virtual reality14–16. Nonlinear dimensionality reduction13 showed that population activity was well-described by approximately four to six latent variables, which suggests that neural activity is constrained to a low-dimensional manifold. Within this low-dimensional space, both physical and abstract variables were jointly mapped in an orderly manner, creating a geometric representation that we show is similar across mice. The existence of conjoined cognitive maps suggests that the hippocampus performs a general computation—the creation of task-specific low-dimensional manifolds that contain a geometric representation of learned knowledge. The hippocampus geometrically represents both physical location and abstract variables on a neural manifold in mice performing a decision-making task in virtual reality.

Geometry of abstract learned knowledge in the hippocampus