Odour encoding in olfactory neuronal networks beyond synchronization.

It has been suggested that odour encoding in olfactory systems occurs by synchronized firing in neuronal populations. Neurons correlated in terms of the Lempel-Ziv distance of spike trains and the sequential superparamagnetic clustering algorithm belong to the same cluster if they show similar, but not necessarily synchronous, firing patterns. Using multielectrode array recordings from the rat olfactory bulb, we have determined cluster incidence and stability in the neuronal network using both the Lempel-Ziv distance and a measure of synchronization. In the Lempel-Ziv paradigm, we found pronounced stabilization and destabilization effects in the neuronal network in response to odour presentation when compared with the synchronization paradigm. This suggests that synchronization alone may be insufficient for understanding olfactory coding.