Trigeminal modulation of olfactory signal processing
The olfactory system displays a high degree of plasticity. Odor sensitivity, odor discrimination, and odor learning are not invariant over time, but they are subject to regulatory processes. These involve modulatory effects on peripheral olfactory receptor neurons, as well as the modulation of signal processing in the olfactory bulb. In recent years, psychophysical experimentation and functional brain studies have revealed that the trigeminal system plays a prominent role in the modulation of olfaction. While the effects of trigeminal activity on olfactory performance are well documented, little is known about the relevant interactions of olfactory and trigeminal systems on the molecular level. The tandem project proposed here is designed to gain insight into the anatomical sites of contact between the two systems, and to identify the molecular pathways that mediate the modulatory trigeminal effects on olfactory signal processing. One group (Müller, Jülich) will conduct a neuroanatomical study of the olfactory-trigeminal system and will investigate the expression of neuropeptide receptors on olfactory neurons. The other group (Frings, Heidelberg) will examine electrophysiologically how neurons in the olfactory epithelium and in the olfactory bulb are modulated by neuropeptides that are released from trigeminal nerve endings.