Another type of spatial neuron found
First of all, I don’t want to mean that a neuron was found in space, but that similarly to the grid cells found by Nobel laureate May-Britt Moser and colleagues another cell type named object-vector cell has been found 1-also by their group- which is involved in spatial sensation. While grid cells are place modulated cells, that help define a coordinate system that allows for spatial navigation, this new type of cell measures the distance and direction to all the objects around us. Obviously the two types of cell interact with one another and the newly discovered ones are the ones basically responsible for avoiding us bumping into objects (I have to say mine are not so finely tuned since I always hit my elbow on door frames…). The researchers recorded firing activity from more than 500 medial entorhinal neurons in the cortex of 8 mice while they were freely exploring an arena looking for cookies (here the most important bit hehe), either circular or square, in which the researchers started introducing objects (namely Duplo blocks and Lego figures) to see if their introduction produced changes in the firing of those neurons. Not only did the firing change by the introduction of the objects, but it also differed depending on direction and distance to the object (vector characteristics). Further, the researchers demonstrated that these cells cannot distinguish between a Lego round tower or a square one, and that they do not need pre-exposure to fire, that is they don’t need training on the object to function. Moreover, they determined that they are independent of the animal’s position, it doesn’t matter if the animal is looking towards the Lego Batman or away from him, these object-vector neutrons will fire (or not) just the same; and they also saw that for these cells it is not important if an object really stands “on the way” or just were visible but not obstructing, which they tested by hanging a lego piece in the wall of the arena so that the mice could see it but still could walk underneath. And finally, they reviewed all the reasons why these cells are distinct from grid cells, border cells or head movement cells and constitute a newly discovered type. In summary, the authors showed that a substantial fraction of medial entorhinal cortex neurons fire specifically when mice are at certain distances and directions from located objects. These ‘object-vector cells’ are tuned to a wide array of objects, irrespective of location, as well as to a broad range of dimensions and shapes (read here from Lego blocks to Batman figures). So here you have another cell population to thank for your ability to navigate the city centre on a Saturday morning, or to avoid falling on your face when trying to cross through a living room full of the above mentioned lego pieces. It is the combined effort of all these cell types (grid cells, border cells, head movement, vector-object and who knows which more) that allows us free movement. So go give your brain a big mental hug. You’re welcome.
- Øyvind Arne Høydal, Emilie Ranheim Skytøen, Sebastian Ola Andersson, May-Britt Moser & Edvard I. Moser (2019) Object-vector coding in the medial entorhinal cortex Nature doi: 10.1038/s41586-019-1077-7 ↩
[…] First of all, I don’t want to mean that a neuron was found in space, but that similarly to the grid cells found by Nobel laureate May-Britt Moser and colleagues another cell type named object-vector cell has been found […]