Organizing conceptual knowledge in humans with a gridlike code

TLDR

The brain is thought to organize concepts into a mental map, with grid cells providing a hexagonally symmetric code that may underlie such spatial‑like representations. Human participants navigating two‑dimensional conceptual knowledge exhibited a stable hexagonal fMRI signal in brain regions analogous to those used for spatial navigation, indicating that nonspatial concepts may be arranged by a global hexagonal grid code.

Abstract

It has been hypothesized that the brain organizes concepts into a mental map, allowing conceptual relationships to be navigated in a manner similar to that of space. Grid cells use a hexagonally symmetric code to organize spatial representations and are the likely source of a precise hexagonal symmetry in the functional magnetic resonance imaging signal. Humans navigating conceptual two-dimensional knowledge showed the same hexagonal signal in a set of brain regions markedly similar to those activated during spatial navigation. This gridlike signal is consistent across sessions acquired within an hour and more than a week apart. Our findings suggest that global relational codes may be used to organize nonspatial conceptual representations and that these codes may have a hexagonal gridlike pattern when conceptual knowledge is laid out in two continuous dimensions.