The brain makes maps of abstract realms.

Underwood summarizes the importance of recent work by Constantinescu et al.

The brain is a mapmaker. As you navigate a landscape, neurons in a region called the entorhinal cortex fire at multiple locations, marking out a hexagonal grid on a mental map. The discovery of these so-called grid cells, and their role as a neuronal GPS for spatial navigation, won the 2014 Nobel Prize in Physiology or Medicine for Norwegian scientists Edvard Moser and May-Britt Moser. Now, it seems that the brain may make maps of abstract realms, too. A team at the University of Oxford in the United Kingdom provides evidence that gridlike neuronal activity throughout the brain helps people organize nonnavigation knowledge—for the purposes of the new study, differences in body shape between various types of birds. Several brain regions, including the entorhinal cortex and the ventromedial prefrontal cortex, showed gridlike neural representation of conceptual space.

The abstract of the article:

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.