Stimulation of the locus ceruleus modulates signal-to-noise ratio in the olfactory bulb

Abstract

Norepinephrine (NE) has been shown to influence sensory, and specifically olfactory processing at the behavioral and physiological levels, potentially by regulating signal-to-noise ratio (S/N). The present study is the first to look at NE modulation of olfactory bulb (OB) inregards toS/Ninvivo. Weshow, inmalerats, that locus ceruleus stimulationandpharmacological infusions of NEintotheOBmodulate both spontaneous and odor-evoked neural responses. NE in the OB generated a non-monotonic dose–response relationship, suppressing mitral cell activity at high and low, but not intermediate, NE levels. We propose that NE enhances odor responses not through direct potentiation of the afferent signal per se, but rather by reducing the intrinsic noise of the system. This has important implications for the ways in which an animal interacts with its olfactory environment, particularly as the animal shifts from a relaxed to an alert behavioral state.