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, 32 (3), 450-60

The Vomeronasal Organ Is Not Involved in the Perception of Endogenous Odors

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The Vomeronasal Organ Is Not Involved in the Perception of Endogenous Odors

Johannes Frasnelli et al. Hum Brain Mapp.

Abstract

Chemosensory-based communication is a vital signaling tool in most species, and evidence has recently emerged in support of the notion that humans also use social chemosignals (so-called pheromones) to communicate. An ongoing controversy does exist, however, concerning the receptor organ through which these chemicals are processed. There is a widespread belief that the vomeronasal organ (VNO) is responsible for processing social chemosignals in humans. Here we demonstrate that functional occlusion of the VNO does not change the percept of, sensitivity toward, or functional neuronal processing of a putative human pheromone. Perithreshold and suprathreshold perception of the endogenous chemical androstadienone (AND) were compared, as were positron emission tomography brain activations evoked by AND when the VNO was either occluded or left open. In addition, we compared sensitivity to AND in subjects with an identifiable VNO to those in whom no VNO could be detected. Thus we could examine the effects of the VNO at several different levels of processing. Occlusion or absence of the VNO did not affect either the perceptual measurements or the functional processing of the putative human pheromone, AND. These results provide strong evidence that the human VNO has no obvious function. Pheromonal communication in humans may be conveyed via the main olfactory system.

Figures

Figure 1
Figure 1
Threshold measurements: mean threshold for AND and CON in subjects with VNO (black bars) and subjects in whom no VNO could be detected (white bars) when the VNO was left open (open) and when the VNO was covered (occluded). Error bars indicate standard error of the mean.
Figure 2
Figure 2
Schematic drawing of the PET procedure: First, under endoscopic control, the patch was placed either on the VNO (VNO occluded) or on the lateral nasal wall (VNO open). Then, after injection of H2O15, subjects were instructed to sniff for 3 s, during which the odor (CON, AND or, in the baseline condition, a blank) was presented by holding a bottle under their nose. Then subjects were instructed to exhale for 5 s, after which the next stimulation cycle began. The whole stimulation period lasted 60 s. After this, subjects rated the odors with regard to intensity, pleasantness, and familiarity.
Figure 3
Figure 3
Global contrasts: Statistical parametric maps (t-statistics as represented by the color scale; note that color scale is inversed in C) superimposed on group averaged anatomical MRI showing group regional CBF response to the processing of (A) the control odor (contrast CON–baseline), (B) androstadienone (contrast AND–baseline). Figure C represents the contrast between regional CBF response to CON and AND (contrast CON– AND). Significant regions are highlighted by colored circles. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

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