The Neural Code for Taste in the Nucleus of the Solitary Tract of Rats with Obesity Following Roux-En-Y Gastric Bypass Surgery.

Previous work has shown that taste responses in the nucleus tractus solitarius (NTS; the first central relay for gustation) are blunted in rats with diet-induced obesity (DIO). Here, we studied whether these effects could be reversed by Roux-en-Y gastric bypass (RYGB) surgery, an effective treatment for obesity. Rats were fed a high energy diet (60% kcal fat; HED) both before and after undergoing RYGB.

Context-dependent odor learning requires the anterior olfactory nucleus.

Learning to associate the context in which a stimulus occurs is an important aspect of animal learning. We propose that the association of an olfactory stimulus with its multisensory context is mediated by projections from ventral hippocampus (vHC) networks to the anterior olfactory nucleus (AON). Using a contextually cued olfactory discrimination task, rats were trained to associate 2 olfactory stimuli with different responses depending on visuospatial context.

Noradrenergic effects on olfactory perception and learning.

We here review modulation of olfactory guided behavioral tasks by noradrenaline. In this review we focus on modulation of the main olfactory system in adult rodents. We detail behavioral paradigms commonly used and discuss how sensory perception and learning can be measured using these paradigms.

Spontaneous Changes in Taste Sensitivity of Single Units Recorded over Consecutive Days in the Brainstem of the Awake Rat.

A neuron's sensitivity profile is fundamental to functional classification of cell types, and underlies theories of sensory coding. Here we show that gustatory neurons in the nucleus of the solitary tract (NTS) and parabrachial nucleus of the pons (PbN) of awake rats spontaneously change their tuning properties across days. Rats were surgically implanted with a chronic microwire assembly into the NTS or PbN.

Odor-taste convergence in the nucleus of the solitary tract of the awake freely licking rat.

Flavor is produced by the integration of taste, olfaction, texture, and temperature, currently thought to occur in the cortex. However, previous work has shown that brainstem taste-related nuclei also respond to multisensory inputs. Here, we test the hypothesis that taste and olfaction interact in the nucleus of the solitary tract (NTS; the first neural relay in the central gustatory pathway) in awake, freely licking rats.

Duration and specificity of olfactory nonassociative memory.

Olfactory habituation is a simple form of nonassociative memory in which responsiveness to stable but behaviorally nonsignificant stimuli is decreased. Olfactory habituation has recently become a paradigm widely used to probe the neural substrate underlying olfactory perception and memory. This simple behavioral paradigm has been used successfully used to probe many aspects of olfactory processing, and it has recently become clear that the neural processes underlying olfactory habituation can depend on the task parameters used.

Noradrenergic but not cholinergic modulation of olfactory bulb during processing of near threshold concentration stimuli.

Neuromodulatory systems such as noradrenaline (NE), acetylcholine (ACh), and serotonin (5HT) serve important functions in sensory perception. We use the olfactory bulb (OB) as a model system to study the roles of individual neuromodulators in sensory perception. Using a spontaneous, nonreward motivated detection task, as well as a reward-motivated task, we show that rats can easily respond to odorants at very low concentrations when motivated to do so in a food-rewarded task, despite not showing spontaneous responses to these low concentration odorants.

Olfactory bulb habituation to odor stimuli.

Habituation is a simple form of memory, yet its neurobiological mechanisms are only beginning to be understood in mammals. In the olfactory system, the neural correlates of habituation at a fast experimental timescale involving very short intertrial intervals (tens of seconds) have been shown to depend on synaptic adaptation in olfactory cortex. In contrast, behavioral habituation to odorants on a longer timescale with intertrial intervals of several minutes depends on processes in the olfactory bulb, as demonstrated by pharmacological studies.

Noradrenergic modulation of behavioral odor detection and discrimination thresholds in the olfactory bulb.

The mammalian main olfactory bulb (MOB) receives a significant noradrenergic input from the locus coeruleus. Norepinephrine (NE) is involved in the acquisition of conditioned odor preferences in neonatal animals and in some species-specific odor-dependent behaviors. Thus far, the role of NE in odor processing in adult rats remains less studied.

Olfactory perceptual learning requires adult neurogenesis.

Perceptual learning is required for olfactory function to adapt appropriately to changing odor environments. We here show that newborn neurons in the olfactory bulb are not only involved in, but necessary for, olfactory perceptual learning. First, the discrimination of perceptually similar odorants improves in mice after repeated exposure to the odorants.

Dopaminergic modulation of olfactory bulb processing affects odor discrimination learning in rats.

Olfactory behavioral studies have shown that, when modulated through systemic injections, D1 and D2 receptors have opposing effects on odor discrimination learning. In the present study, cannulated male Sprague-Dawley rats were used to investigate how the modulation of these 2 types of dopaminergic receptors through direct infusion of D1/D2 agonists and antagonists into the olfactory bulb affect olfactory perception. Dopaminergic modulation was locally altered by manipulations of D1 (agonist SKF 82958: 14.

Bulbar acetylcholine enhances neural and perceptual odor discrimination.

Experimental and modeling data suggest that the circuitry of the main olfactory bulb (OB) plays a critical role in olfactory discrimination. Processing of such information arises from the interaction between OB output neurons local interneurons, as well as interactions between the OB network and centrifugal inputs. Cholinergic input to the OB in particular has been hypothesized to regulate mitral cell odorants receptive fields (ORFs) and behavioral discrimination of similar odorants.

Odor-reward learning and enrichment have similar effects on odor perception.

We compared the respective effects of odor enrichment and reward-driven discrimination learning on the perception of odors. Experimental rats were exposed to two odorants for 1-h periods once daily over 10 days, or trained with the same two odorants in a forced-choice discrimination task during a daily 20 trial session over 10 days. Spontaneous discriminations between pairs of chemically similar odors were tested before and after the odor enrichment period using an olfactory habituation/discrimination task.

Modified spike-triggered averaging to assess rat auditory cortex time-frequency receptive fields.

Receptive fields have been used as a tool to study the functional organization of the auditory system in several animals. In this study, they have been used to characterize the primary auditory cortex of rats, specifically to address the differences in auditory processing at different depths of the cortex. The depths chosen; 500, 800 and 1300 microm correspond to layers IV, V and VI of the cortex.