Delving into the depths of cortical space
How does our brain figure out where we are in relation to our surroundings? The EU-funded project SPACEBRAIN shed light on this and other questions by exploring specific neural cells in the brain. The findings contributed to three of the team members being awarded the Nobel Prize in Physiology or Medicine in 2014.
© Rawpixel.com – fotolia.com
In the 1970s, neuroscientist John O’Keefe discovered the so-called ‘place cell’, a type of neuron located in the hippocampus section of the brain. Place cells become active when we enter a particular place. In 2005, his colleagues May-Britt Moser and Edvard Moser found another type of cell in the entorhinal cortex that they dubbed the ‘grid cell’. All three collaborated on the SPACEBRAIN project.
“Those cells provide a kind of matrix almost like a coordinate system that the brain uses to map location,” explains SPACEBRAIN coordinator and Nobel Prize laureate Edvard Moser of the Norwegian University of Science and Technology. “The aim was to try to understand better how these grid cells work, how they develop, talk to each other and work together to create a feeling of space.”
This is what the SPACEBRAIN consortium found: similar to place cells, grid cells fire, i.e. become active, at multiple specific positions in our environment. “When an animal walks around inside a box, the cell is only active in specific locations, but those specific locations form a hexagonal network all across space,” says Moser.
Drawing an internal map
This network is thought to be part of the brain’s metric or measurement system for space, which helps us judge distances and directions. Thousands and thousands of grid cells are constantly updated as we move around. If we move left, one set of grid cells is active, while another takes over if we move right or forward. Together grid, place, border, head-direction and the more recently discovered speed cells help our brain establish an internal map.
The SPACEBRAIN researchers proved that place cells and head-direction cells in animals develop very early on, almost as soon as they start moving around after birth. Grid cells are present at the same time but do not reach a mature state until 1-2 weeks later.
On top of this scientific progress and advances in computational modelling, SPACEBRAIN also made technical headway. The project developed microdrives for recording electrical activity in multiple brain locations simultaneously, and contributed to the development of technology for high-resolution imaging by means of tiny portable microscopes. Based on parallel work in other groups, the latter is becoming a standard imaging technique used in many labs the world over.
Insights into neurological and psychiatric diseases
But what do these findings mean? “Alzheimer’s disease in many cases starts in exactly the same brain area that contains these grid cells and this spatial network,” Moser explains. “If you understand how this brain area works, you may be able to also identify signs of Alzheimer very early on and then interfere before it is too late.”
Efforts to improve our understanding of how the brain computes information are ongoing, attempting to link psychological concepts such as memory and decision-making to their physiological counterparts. “Our work on cortical computations and neural networks is relevant to understanding all parts of the brain, especially the cortex,” Moser points out. “That’s relevant to all kinds of neurological and psychiatric diseases, so that the more long-term mission actually takes us far beyond Alzheimer’s.”
The Nobel Prize committee awarded half of the Nobel Prize in Physiology or Medicine 2014 to John O’Keefe and the other half to May-Britt Moser and Edvard Moser “for their discoveries of cells that constitute a positioning system in the brain". While these discoveries took place before the project, Edvard Moser still considers SPACEBRAIN an important step along the way: it offered the researchers an opportunity to collaborate closely, helping them to refine their understanding of these cells, and contributed to bridging the gap between theoretical/computational neuroscience and the rest of the field.