Functional coupling in rat central olfactory pathways: a coherence analysis.

This experiment determined the importance of functional coupling between structures of central olfactory pathways: the olfactory bulb (OB), anterior (APC), posterior (PPC) parts of the piriform cortex and lateral entorhinal cortex (EC). From local field potential signals obtained in awake rats, coupling during spontaneous activity was estimated with variables reflecting level of coherence computed with a dynamical method. Results revealed a clear hierarchy in the strength of coupling between structures with dissociation within the piriform cortex: PPC was more tightly coupled with the EC than with APC. Systemic injection of a cholinergic antagonist, scopolamine, suggested that tonic coupling is strongly mediated by cortico-cortical connections and not by an external synchronizer, except between OB and APC.