Trigeminal perception is necessary to localize odors

Bubble dynamics in various commercial sparkling bottled waters

“…Carbonation, or the perception of dissolved CO 2 , indeed involves a truly very complex multimodal stimulus (Lawless and Heymann, 2010). During carbonated beverage tasting, dissolved CO 2 acts on both trigeminal receptors (Dessirier et al, 2000;Kleeman et al, 2009;Meusel et al, 2010), and gustatory receptors, via the conversion of dissolved CO 2 to carbonic acid (Chandrashekar et al, 2009;Dunkel and Hofmann, 2010), in addition to the tactile stimulation of mechanoreceptors in the oral cavity (through bursting bubbles). More recently, Wise et al (2013) showed that the carbonation bite was rated equally strong with or without bubbles under normal or higher atmospheric pressure, respectively.…”

Stereo and serial sniffing guide navigation to an odour source in a mammal

“…Of these two possibilities, the possible contribution of simultaneously compared bilateral cues during odorant localization has been a topic of much historical interest and recent investigation [6][7][8][9][10][11][12][13][14][15][16][17] . Evidence for bilateral comparisons in humans comes from degraded scent-tracking abilities during unilateral nostril blockade or a fused airway 18 , but other studies suggest that nostril-specific odorant localization by humans requires trigeminal stimulation 13,16 . Studies of trained rats found that bilateral sampling was necessary for determining the side from which an odorant arrived 10 , and investigation of neurons in the rodent anterior olfactory nucleus reveal the neural circuitry that could underlie bilateral comparisons 9 .…”

Human Olfactory Perception

“…100 The ability to lateralize an odorant stimulus delivered to a single nostril is taken as evidence for trigeminal activation by that stimulus. 23,101 Intranasal carbon dioxide is a stimulus often used to activate the trigeminal pathway and map the central neural structures responding to trigeminal stimuli in humans. 102 These considerations lead to the identification of a few odorants as purely olfactory and many other odorants as mixed stimulants for both the olfactory and trigeminal pathways, at least at moderate to high concentrations.…”

“…15 Human olfactory ability is often viewed as of minor importance relative to other distal sensory modalities such as vision or audition. This facile view underestimates the actual extent of human olfactory sensitivity 16,17 and neglects the role of olfaction in many aspects of human interactions, including social communication, 18,19 mate choice, 20,21 scent tracking and odour localization, [22][23][24] flavour evaluation and retronasal olfaction, 25 subcortical effects on response selection, 26,27 olfactory effects on food selection, 28 olfactory alterations in pregnancy, 29,30 epigenetic transmission of odour preferences 31,32 and protective alarm responses, 33 among others. Even though a variety of genetic mechanisms have limited the repertoire of expressed human olfactory receptor genes, 34 the several hundred human olfactory receptor genes that are expressed represent the largest gene superfamily in the human genome 35 and provide ample combinatorial and computational complexity for molecular recognition and pattern analysis far beyond any technical device yet known.…”