Cockroach olfactory bulb response to novel stimuli I've heard anecdotally, that the cockroach olfactory bulb responds differently to novel stimuli vs. known stimuli. Specifically, it sends an oscillatory firing pattern for known stimuli and a constant firing pattern for novel stimuli. However, I'm having a hard time finding a reference for this? Does the olfactory bulb in insects (not just cockroaches) actually respond with different firing patterns?
According to Kay and Stopfer (2006) in their paper, Information processing in the olfactory systems of insects and vertebrates, it looks as though oscillatory firing patterns in insects fire as a mechanism for categorizing all smells, novel and familiar:


  Several imaging techniques that assess afferent or principal neuron 
  responses all indicate that odor stimulation evokes maps of activity 
  that vary with the odorant; not all odorants activate all glomeruli and principal neurons.


More specifically:


  In both insects and vertebrates, odor stimulation elicits the oscillatory synchronization of responsive principal neurons.


Note that no distinction is being made here between novel and familiar olfactory stimuli. It seems that much of the research on novel olfactory stimuli as related to olfactory bulb firing patterns has been done on vertebrates, as discussed here.