Scientists have coined different terms to describe network phenomena observed using a variety of recording techniques in different brain regions and species, sometimes in vivo and other times in vitro (Table Network event terminology). In retrospect, it is apparent that several of these terms refer to the same biological phenomenon. For example, spindle bursts and early network oscillations both refer to correlated activity of cortical neurons in newborn rodents, but one describes events recorded with electrophysiology, while the other refers to events detected with calcium imaging. Another problem is that some of the terms chosen to describe correlated activity are sometimes inaccurate, or too specific. For example, to a novice in the field the term ‘oscillation’ might mean that the network events reoccur in a predictably repetitive, perhaps even rhythmic fashion, but this is clearly not the case (even if within individual bursts there is some oscillatory activity), as correlated activity is organized in a temporally discontinuous manner. Similarly, the terms giant depolarizing potential and spindle burst describe the local field potential during network events but tell us nothing about the degree of synchrony across different neurons or about the spatial organization of network events.
Considering the complexity of neuronal activity during development (from the more local patchwork activity to the larger wave-like events), we propose the term correlated network activity (CNA). This term more accurately depicts the fact that neuronal firing is synchronous within the network, which is the unifying characteristic that defines them. CNA would refer to correlated neuronal activity involving most neurons within a local network, either in small clusters or propagating as waves across a larger cortical region; the recorded activity should be mediated by action potentials (chemical synapses).