Novel fantastic research about 3D grid cells in the human brain by Dr. Misun Kim and Professor Eleanor A. Maguire in paper Kim et al. 2019 

Misun Kim, Eleanor A. Maguire. Can we study 3D grid codes non-invasively in the human brain?Methodological considerations and fMRIfindings. NeuroImage Volume 186, 1 February 2019, Pages 667-678

Recent human functional magnetic resonance imaging (fMRI) and animal electrophysiology studies suggest that grid cells in entorhinal cortex are an efficient neural mechanism for encoding knowledge about the world, not only for spatial location but also for more abstract cognitive information. The world, be it physical or abstract, is often high-dimensional, but grid cells have been mainly studied on a simple two-dimensional (2D) plane.

Recent theoretical studies have proposed how grid cells encode three-dimensional (3D) physical space, but it is unknown whether grid codes can be examined non-invasively in humans.

The latest research by Misun Kim and Eleanor A. Maguire investigated whether it was feasible to test different 3D grid models using fMRI based on the direction-modulated property of grid signals. In doing so,they developed interactive software to help researchers visualize 3D grid fields and predict grid activity in 3D as a function of movement directions.

They found that a direction-modulated grid analysis was sensitive to one type of 3D grid model–a face-centred cubic (FCC) lattice model. As a proof of concept, they searched for 3D grid-like signals in human entorhinal cortex using a novel 3D virtual reality paradigm and a new fMRI analysis method. They found that signals in the left entorhinal cortex were explained by the FCC model. This is preliminary evidence for 3D grid codes in the human brain, not with standing the inherent methodological limitations of fMRI. They believe that their findings and software serve as a useful initial stepping-stone for studying grid cells in realistic 3D worlds and also, potentially, for interrogating abstract high-dimensional cognitive processes.

For further info, please read the paper Kim et al. 2019.

Misun Kim, Eleanor A. Maguire. Can we study 3D grid codes non-invasively in the human brain?Methodological considerations and fMRIfindings. NeuroImage Volume 186, 1 February 2019, Pages 667-678

Kim, Misun; (2018) Three-dimensional space representation in the human brain. Doctoral thesis (Ph.D), UCL (University College London).

3D Grid Cells Visualisation Software https://www.fil.ion.ucl.ac.uk/Maguire/grid3D_gui/