State-dependent coherences between the olfactory bulbs for delta and theta oscillations.

Correlations of neuronal oscillations in different brain regions are closely related to a variety of brain functions. The delta and theta oscillations in the olfactory bulb (OB), coupled with respiration rhythm, could play important roles in olfactory tasks. The correlations between the two OBs, however, are largely unknown. By simultaneously recording local field potentials from the OBs, we found that for these oscillations, the intrabulbar coherences were high and state-independent, while the interbulbar coherences were also high but state-dependent. Higher activity states, generated by lighter depth of anesthesia or peripheral odor stimulation, have lower coherence, suggesting that the high interbulbar correlations can be modulated by both internal and external factors.