  A classical view of neural coding relies on temporal firing synchrony among
functional groups of neurons; however the underlying mechanism remains an
enigma. Here we experimentally demonstrate a mechanism where time-lags among
neuronal spiking leap from several tens of milliseconds to nearly zero-lag
synchrony. It also allows sudden leaps out of synchrony, hence forming short
epochs of synchrony. Our results are based on an experimental procedure where
conditioned stimulations were enforced on circuits of neurons embedded within a
large-scale network of cortical cells in vitro and are corroborated by
simulations of neuronal populations. The underlying biological mechanisms are
the unavoidable increase of the neuronal response latency to ongoing
stimulations and temporal or spatial summation required to generate evoked
spikes. These sudden leaps in and out of synchrony may be accompanied by
multiplications of the neuronal firing frequency, hence offering reliable
information-bearing indicators which may bridge between the two principal
neuronal coding paradigms.
