Figure 2. Competitive neural networks and basic network excitation-inhibition coordination.

In these schemes, each cell type that is depicted, principal cell (PC) and inhibitory interneuron (IN), represents a population of the cell type, not an individual neuron. Cells that are mutually excitatory, and therefore more likely to be coactive, are color coded either red or blue; the red and blue cells will tend not to be coactive. Activity amongst the red cells, by virtue of the connectivity, will tend to recruit and enhance activity amongst red cells, and suppress activity of the blue cells. A) Left - In a properly- configured competitive network, once excitation and inhibition are appropriately balanced in the network, any bias in activity in favor of the red or blue cells will cause the more active subset to increase activation and suppress the other, competing pattern of activity. Right - Despite receiving similar inputs, the hypothetical spatial discharge of the red and blue cells would tend to occupy, and therefore represent, distinct places because of the competitive neural dynamics. The firing field will tend to be discrete. B) Left - Dysplasticity, such as by increasing connectivity between the competing rarely coactive (red versus blue) neurons can corrupt the network causing dysfunction, so that the red and blue activity patterns are less distinctive. Right - Spatial representations in the corrupted network are consequently less distinctive, generating diffuse firing fields that tend to overlap.