Graded persisting activity of heterogeneous neuron ensembles subject to white noises

Effects of distractions such as noises and parameter heterogeneity have been studied on the firing activity of ensemble neurons, each of which is described by the extended Morris-Lecar model showing the graded persisting firings with the aid of an included ${\rm Ca}^{2+}$-dependent cation current. Although the sustained activity of {\it single} neurons is rather robust in a sense that the activity is realized even in the presence of the distractions, the graded frequency of sustained firings is vulnerable to them. It has been shown, however, that the graded persisting activity of {\it ensemble} neurons becomes much robust to the distractions by the pooling (ensemble) effect. When the coupling is introduced, the synchronization of firings in ensemble neurons is enhanced, which is beneficial to firings of target neurons.