Odorants can activate the nasal epithelium from two directions, either orthonasally from the nares via nasal breathing or sniffing or retronasally through the mouth during eating and drinking. Retronasal olfaction is associated with a higher threshold for detection than orthonasal olfaction, and a different pleasantness rating. Rozin (1982) proposed that there exists a duality of olfactory perception via the two olfactory routes. Recent electrophysiological and imaging studies showed odorants entering the retronasal olfactory route elicit different peripheral neural responses in the glomerulus and mitral cell firing in the olfactory bulbs (OB). Functional networks engaged in retronasal olfaction also show differential activities in higher cortical regions, which may underlie the perceptual differences between the two routes. Here, I use olfactory learning behavioral and electrophysiological studies to study the perceptual qualities of the two olfactory routes and circuit interactions. In Chapter 3, rats were pre-conditioned to odorized solutions delivered only retronasally and then tested in an orthonasal Go/No-Go odor discrimination task. I found significant learning rate improvement for the retronasally pre-exposed odorants in a volatility-dependent manner, and the result suggests that retro- and orthonasal routes can generate similar perceptual qualities if the odors are strong enough. Chapters 4 and 5 describe a retronasal Go/No-Go behavioral experiment in conjunction with local field potential (LFP) recordings in the olfactory and gustatory systems - piriform cortex, gustatory cortex, and olfactory tubercle. I characterize the respiratory and licking behaviors and the oscillation patterns in the gamma (45-100Hz) and beta (15-30 Hz) frequency bands during the retronasal odor discrimination task. Gamma band power is significantly suppressed while beta band power demonstrates an odor-cue effect between the positively and negatively reinforced retronasal odorants. LFPs recorded OB, OT, PC, and GC show coupling with the sensorimotor inputs and are coherent in the beta band during the retronasal odor sampling period. I explore the LFPs during sleep and the effect of olfactory training in Chapter 6. With a sleep scoring algorithm of OB gamma and hippocampal LFP, I compare the sleep pattern pre- and post-olfactory training, showing behavioral difference in sleep time. Together, I wish to shed some light on the neural dynamics in retronasal olfaction.