Attentional modulation of desensitization to odor

Nicholas Fallon,Andrej Stancak,Timo Giesbrecht

doi:10.3758/s13414-018-1539-2

Nicholas Fallon, Andrej Stancak + Show 1 more

Open Access

https://doi.org/10.3758/s13414-018-1539-2

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Abstract

Subjective and behavioral responsiveness to odor diminishes during prolonged exposure. The precise mechanisms underlying olfactory desensitization are not fully understood, but previous studies indicate that the phenomenon may be modulated by central-cognitive processes. The present study investigated the effect of attention on perceived intensity during exposure to a pleasant odor. A within-subjects design was utilized with 19 participants attending 2 sessions. During each session, participants continuously rated their perceived intensity of a 10-minute exposure to a pleasant fragrance administered using an olfactometer. An auditory oddball task was implemented to manipulate the focus of attention in each session. Participants were instructed to either direct their attention toward the sounds, but still to rate odor, or to focus entirely on rating the odor. Analysis revealed three 50-second time windows with significantly lower mean intensity ratings during the distraction condition. Curve fitting of the data disclosed a linear function of desensitization in the focused attention condition compared with an exponential decay function during distraction condition, indicating an increased rate of initial desensitization when attention is distracted away from the odor. In the focused-attention condition, perceived intensity demonstrated a regular pattern of odor sensitivity occurring at approximately 1−2 minutes intervals following initial desensitization. Spectral analysis of low-frequency oscillations confirmed the presence of augmented spectral power in this frequency range during focused relative to distracted conditions. The findings demonstrate for the first time modulation of odor desensitization specifically by attentional factors, exemplifying the relevance of top-down control for ongoing perception of odor.

Highlights

Subjective and behavioral responsiveness to odor diminishes during prolonged exposure
Attention can be directed toward olfaction in a similar fashion to other sensory modalities (Keller, 2011), and the composition of perceived Bodor objects^ can be influenced by top-down processes (Wilson & Sullivan, 2011)
The findings demonstrate the effects of focused attention on odor desensitization, comprising a slower and linear decrease in perceived odor intensity during the first minute of odor exposure when attention was focused toward the odor, compared with a steeper, exponential decay seen in the distraction condition

Summary

Introduction

Subjective and behavioral responsiveness to odor diminishes during prolonged exposure. Eletro-olfactogram recordings directly from olfactory receptors demonstrated that behavioral desensitization is independent from adaptation in the periphery (Hummel et al, 1996), and functional magnetic resonance imaging (fMRI) studies revealed blood-oxygen-level-dependent (BOLD) signal changes associated with desensitization to odor stimuli that were predominantly encoded in primary olfactory cortices (Poellinger et al, 2001) Despite this functional and semantic demarcation, it is clear that central and peripheral processes occur in parallel and share a complex relationship (Pellegrino, Sinding, de Wijk, & Hummel, 2017), and it is their cumulative effects that determine subjective changes in perception (Dalton, 2000). A within-subjects design was utilized, and an auditory oddball task was employed to manipulate focus of attention during the period of olfactory desensitization

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