Calcium imaging and multielectrode recordings of global patterns of activity in the developing nervous system

Complex but coordinated interactions involving ensembles of neuronal cells result in the accurate processing of information in the adult central nervous system. However, recent studies monitoring the global patterns of activity of neuronal populations have demonstrated that immature neurons also interact to produce coordinated patterns of activity during the early stages of development. In particular, these patterns of coordinated activity occur during the period when neuronal connections are established, thus leading us to believe that such activity patterns might underlie the precision to which many neural pathways are wired up. Multielectrode recording and calcium imaging are two of the techniques that have been instrumental in revealing the spatial and temporal properties of the coordinated activity of developing neural networks in vitro. While multielectrode arrays measure the action potential activity of the cells, calcium imaging permits changes in intracellular calcium levels to be monitored over time. Both techniques have been used successfully to monitor the activity of cellular networks in culture, but they have also been applied in assessing the patterns of activity in intact or semi-intact pieces of neural tissues, such as the developing retina, neocortex and spinal cord. More recently, it has also been possible to correlate the structure and function of the cellular components of the networks by combining intracellular dye filling with the multineuronal recordings. In this review, brief descriptions and the applications of the two techniques will be presented, and the advantages and limitations of multielectrode array will be compared with that of calcium imaging using recordings of the developing mammalian retina as the primary example.