Functional neuromodulation of chemosensation in vertebrates

Abstract

Neuromodulation can be defined as a biophysical process that serves to modify – or modulate - the computation performed by a neuron or network as a function of task demands and behavioral state of the animal. These modulatory effects often involve substances extrinsic to the network under observation, such as acetylcholine (ACh), norepinephrine (NE), histamine, serotonin (5-HT), dopamine (DA), and a variety of neuropeptides. Olfactory and gustatory processes especially need to be adaptive and respond flexibly to changing environments, availability of resources and physiological needs. It is therefore crucial to understand the neuromodulatory processes that regulate the function of these systems.

Preservation of Essential Odor-Guided Behaviors and Odor-Based Reversal Learning after Targeting Adult Brain Serotonin Synthesis

“…The olfactory system is innervated by numerous neuromodulatory systems. These systems, including dopamine, acetylcholine, and, as explored herein, 5-HT, are hypothesized to provide critical refinements to the function of the olfactory system within the olfactory bulb, as well as in secondary and tertiary olfactory-processing stages (Linster and Fontanini, 2014). For instance, multiple lines of elegant work have revealed that cholinergic modulation within the olfactory bulb and downstream piriform cortex impacts fine odor discrimination, short-term odor memory, odor-based rule learning, and odor habituation (Ravel et al, 1992; Saar et al, 2001; Fletcher and Wilson, 2002; Linster and Cleland, 2002; Mandairon et al, 2006; Chaudhury et al, 2009).…”

“…In this manner, top-down centers that produce neuromodulators can differentially release these modulators in sensory centers depending on the needs of the animal. Major questions remain, however, regarding what neuromodulators are necessary for normal sensory system function (Katz, 1999; Hurley et al, 2004; Bouret and Sara, 2005; Linster and Fontanini, 2014). …”

Divergent innervation of the olfactory bulb by distinct raphe nuclei

“…The nucleus‐specific innervation pattern we observe here is reminiscent of largely nonoverlapping projection patterns from the raphe to other brain areas (Steinbusch, ; Jacobs and Azmitia, ). In addition, the GL and the GCL likely implement distinct functions within the OB, for example gating incoming signals in the GL (Petzold et al, ), or transforming signals on different timescales (Fukunaga et al, ; Linster and Fontanini, ). Whether the distinct projection patterns by the raphe translate to modulation of specific combination of areas or circuits within a region, and as a result distinct sets of functions, remains to be investigated.…”

Oxytocin modulation of neural circuits for social behavior

“…Odor-dependent social learning relies on neuromodulation in the olfactory system (Linster and Fontanini, 2014;Choe et al, 2015). Most recently, it has been shown that oxytocin plays a central role in both appetitive and aversive social odor learning via direct modulation of the piriform cortex (Choe et al, 2015).…”