A Multisensory Network for Olfactory Processing.

Primary gustatory cortex (GC) is connected (both mono- and polysynaptically) to primary olfactory (piriform) cortex (PC)-connections that might be hypothesized to underlie the construction of a "flavor" percept when both gustatory and olfactory stimuli are present. Here we use multisite electrophysiology and optical inhibition of GC neurons (GCx, produced via infection with ArchT) to demonstrate that, indeed, during gustatory stimulation, taste-selective information is transmitted from GC to PC. We go on to show that these connections impact olfactory processing even in the absence of gustatory stimulation: GCx alters PC responses to olfactory stimuli presented alone, enhancing some and eliminating others, despite leaving the path from nasal epithelium to PC intact. Finally, we show the functional importance of this latter phenomenon, demonstrating that GCx renders rats unable to properly recognize odor stimuli. This sequence of findings suggests that sensory processing may be more intrinsically integrative than previously thought.