Cortical Hub for Flavor Sensation in Rodents.

Chad L Samuelsen,Roberto Vincis

doi:10.3389/fnsys.2021.772286

Chad L Samuelsen, Roberto Vincis

Open Access

https://doi.org/10.3389/fnsys.2021.772286

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Abstract

The experience of eating is inherently multimodal, combining intraoral gustatory, olfactory, and somatosensory signals into a single percept called flavor. As foods and beverages enter the mouth, movements associated with chewing and swallowing activate somatosensory receptors in the oral cavity, dissolve tastants in the saliva to activate taste receptors, and release volatile odorant molecules to retronasally activate olfactory receptors in the nasal epithelium. Human studies indicate that sensory cortical areas are important for intraoral multimodal processing, yet their circuit-level mechanisms remain unclear. Animal models allow for detailed analyses of neural circuits due to the large number of molecular tools available for tracing and neuronal manipulations. In this review, we concentrate on the anatomical and neurophysiological evidence from rodent models toward a better understanding of the circuit-level mechanisms underlying the cortical processing of flavor. While more work is needed, the emerging view pertaining to the multimodal processing of food and beverages is that the piriform, gustatory, and somatosensory cortical regions do not function solely as independent areas. Rather they act as an intraoral cortical hub, simultaneously receiving and processing multimodal sensory information from the mouth to produce the rich and complex flavor experience that guides consummatory behavior.

Highlights

Eating is a multisensory experience (Small et al, 2004; Small, 2012; Prescott, 2015; Spence, 2015)
Throughout this review, we will emphasize the critical gaps in knowledge that require further investigation to better understand the neural substrates underlying the multimodal processing of flavor
Most sensory neuroscience studies employ unimodal stimuli to investigate sensory processing. These findings provide the foundation for probing the circuit mechanisms underlying the multimodal processing of intraoral stimuli subtending the perception of flavor

Summary

INTRODUCTION

Eating is a multisensory experience (Small et al, 2004; Small, 2012; Prescott, 2015; Spence, 2015). Non-volatile chemicals (i.e., tastants) dissolve in the saliva to activate taste receptors primarily located in the tongue This sensory information is transmitted centrally along separate pathways, but the integration of these three intraoral senses into a unitary object generates the perception of flavor (Small, 2012). Recent findings from animal model studies are beginning to elucidate the neural substrates underlying the multimodal processing of flavor. We describe the anatomical features of the three primary sensory cortical regions subtending flavor sensation (i.e., piriform cortex, gustatory cortex, and somatosensory cortex), paying particular attention to studies examining the direct corticocortical connectivity between them. We discuss the evidence from recent studies highlighting the capacity of the three sensory cortical regions to process multimodal information related to flavor. Throughout this review, we will emphasize the critical gaps in knowledge that require further investigation to better understand the neural substrates underlying the multimodal processing of flavor

ANATOMY AND CONNECTIVITY OF THE THREE PRIMARY SENSORY CORTICAL REGIONS

UNIMODAL PROCESSING

MULTIMODAL PROCESSING

FINAL REMARKS