Measuring the Amount of Concomitant Firing during Neural Development

The aim of this work was to estimate and compare the amount of concomitant firing in the neural dynamics of dissociated in-vitro cultures analyzed across various stages of development. To this end, we used a recently proposed index to estimate the degree of concomitant neural activity (denoted as CFIMI), which computes the mutual information between pairs of state flows extracted from neural spiking activities. The state-flow representation was obtained classifying the spiking activity of each neural unit into three states which differentiate the inter-spike intervals on the basis of their duration using percentile statistics. We show that the CFIMI index detects a significant increase of synchronous (concomitant) firing patterns between pairs of neurons, moving from the early stage of development to intermediate and full maturation in population of thirteen analyzed cultures. Furthermore, the use of the CFIMI index as an estimate of the neural interactions facilitates effective characterization of the functional organization of developing neural networks by graph-theoretic measures.