To improve the performance of the LVQ1, it was found that an output neuron grid size of 25 × 1 which represents the different class is most favorable for this study.
During training, one repeatedly (1) presents individual MeSH-document vectors to the neuron grid and identifies the neuron vector to which it is most similar (using cosine similarity), and then (2) pulls that best-matching neuron and its neighboring neurons even closer towards the input document vector.
Consequently, he and his team at the Norwegian University of Science and Technology in Trondheim have dubbed these previously unknown neurons "grid cells".
There are four known types of navigation-related neurons: grid cells, border cells, place cells, and head direction cells.
Thirty-five years later, neuroscientists May-Britt and Edvard Moser, now at the Norwegian University of Science and Technology in Trondheim, Norway, discovered a separate group of neurons, called grid cells, which fire at regular intervals as rats traverse an open area, creating a hexagonal grid with coordinates similar to those in GPS.
Grid fields may also fail to form if overall activity levels are too low, in which case neurons with grid fields instead encode head direction (Bonnevie et al., 2013).
For each neuron on the grid we can find out the location of its receptive field center in visual space (as defined by its center-of-mass).
Moser's royal blue evening gown, designed by engineer-turned-fashion-designer Matthew Hubble, was adorned with silver leather piping and glittery beadwork to represent the grid neurons, reports Scientific American.
Indeed, we have obtained evidence that place neurons (place and grid cells in the mammalian hippocampus and entorhinal cortex, respectively) encode horizontal space to a high degree of precision but encode vertical space only weakly, if at all [6].
Because there are at least scores of neurons in each grid module (Stensola et al., 2012) P(x| i) can be approximated as a periodic sum of Gaussians without making restrictive assumptions about the shapes of the tuning curves of individual grid cells, or about the precision of their periodicity, so long as the variability of individual neurons is weakly correlated and homogeneous.
The neurons fired at distinct places: If plotted on a map of the enclosure, the firing locations of each neuron formed a triangular grid.
