The effect of verbal context on olfactory neural responses

Abstract

Odor names refer usually to "source" object categories. For example, the smell of rose is often described with its source category (flower). However, linguistic studies suggest that odors can also be named with labels referring to categories of "practices". This is the case when rose odor is described with a verbal label referring to its use in fragrance practices ("body lotion," cosmetic for example). It remains unknown whether naming an odor by its practice category influences olfactory neural responses differently than that observed when named with its source category. The aim of this study was to investigate this question. To this end, functional MRI was used in a within-subjects design comparing brain responses to four different odors (peach, chocolate, linden blossom, and rose) under two conditions whereby smells were described either (1) with their source category label (food and flower) or (2) with a practice category label (body lotion). Both types of labels induced activations in secondary olfactory areas (orbitofrontal cortex), whereas only the source label condition induced activation in the cingulate cortex and the insula. In summary, our findings offer a new look at olfactory perception by indicating differential brain responses depending on whether odors are named according to their source or practice category.

Keywords: context; fMRI; olfaction; smell; verbal.

Figure 1

Experimental design and protocol. (a) The experimental design included four olfactory stimuli (linden blossom, rose, peach, and chocolate) presented under two label conditions (source or practice). (b) Schematic representation of the experimental protocol used during the scanning sessions. [Color figure can be viewed in the online issue, which is available at http://wileyonlinelibrary.com.]

Figure 2

Effect on verbal labeling on sniffing. (a) Odorant tubing and nasal sniffing cannula used to record sniffing. (b) Typical sniffing trace for a subject during an ON period. Sniff duration (c) and sniff volume (d) under the practice label condition and the source label condition. Each circle corresponds to a subject. No significant differences in sniff duration or sniff volume were observed between the two conditions (P > 0.05). [Color figure can be viewed in the online issue, which is available at http://wileyonlinelibrary.com.]

Figure 3

Perceptual ratings and brain activations during the source label condition and the practice label condition. Odor pleasantness (a) and intensity (b) ratings under the practice label condition and the source label condition. Each circle corresponds to a subject. No differences in pleasantness or intensity were observed between the two conditions (P > 0.05). (c) Activation patterns to the source label condition: brain activations were observed in medial orbitofrontal gyrus (OFC), anterior cingulate cortex (CIN), and insula (INS). (d) Activation patterns to the practice label condition: brain activations were observed in medial orbitofrontal gyrus.

Figure 4

Activation pattern to the source label condition vs. the practice label condition. (a) Brain activations were observed in anterior cingulate cortex (CIN). Fitted (b) and raw (c) event related responses in the functionally activated voxels in anterior cingulate gyrus for the source label condition (blue line) and the practice label condition (red line).

Figure 5

Brain activations during the source label condition and the practice label condition for both food odors and flower odors. (a) Activation patterns to the source label condition for the food odors: brain responses were seen in medial orbitofrontal gyrus (OFC), anterior cingulate cortex (CIN) and insula (INS). (b) medial orbitofrontal activation (OFC) in response to the practice label for the food odors. (c) medial orbitofrontal (OFC) and cingulate cortex (CIN) activations in response to the source label for the flower odors.