Involvement of the left anterior insula and frontopolar gyrus in odor discrimination

Abstract

Discriminating between successively presented odors requires brief storage of the first odor's perceptual trace, which then needs to be subsequently compared to the second odor in the pair. This study explores the cortical areas involved in odor discrimination and compares them with findings from studies of working-memory, traditionally investigated with n-back paradigms. Sixteen right-handed subjects underwent H(2) (15)O positron emission tomography during counterbalanced conditions of odorless sniffing, repeated single odor detection, multiple odor detection, and conscious successive discrimination between odor pairs. Eight odorants were delivered using a computer-controlled olfactometer through a birhinal nasal cannula. Conscious successive odor discrimination evoked significantly greater activity in the left anterior insula and frontopolar gyrus when compared to reported sensory detection of the identical odors. Additional activation was found in the left lateral orbital/inferior frontal and middle frontal gyri when discrimination was compared to the odorless condition. The left anterior insula is likely involved in the evaluation of odor properties. Consistent with other studies, frontopolar and middle frontal gyrus activation is more likely related to working memory during odor discrimination.

Neuroleptic-induced parkinsonism is associated with olfactory dysfunction

“…While odor threshold and identification processing is reported to involve the basal ganglia, especially the caudate nucleus [14], odor discrimination has been reported to be modulated in left anterior insula, frontopolar and temporal gyri [34]. D2-blocking agents exert their mechanism of action also via the nigrostriatal pathways.…”

How Pleasant and Unpleasant Stimuli Combine in Different Brain Regions: Odor Mixtures

“…However, these studies have not explicitly investigated interactions between pleasant and unpleasant odors in parts of the olfactory system where the affective value of odors is represented. Furthermore, although neuroimaging studies have provided important insights into the processing of olfactory information in the human brain (Zatorre et al, 1992;Zald and Pardo, 2000;Poellinger et al, 2001;Small et al, 2005;Gottfried et al, 2006;Li et al, 2006;Plailly et al, 2007), including the representation of the hedonic value of odors (Zatorre et al, 2000;Savic et al, 2001;Anderson et al, 2003;Rolls et al, 2003;Royet et al, 2003;de Araujo et al, 2005;Winston et al, 2005), we know of no previous neuroimaging studies in humans that have compared the effects of a mixture with those of its components. Overall, little is known about the interactions between the pleasant and unpleasant components of stimuli in any modality, and how these influence de-cision making, and olfaction provides a good model for investigation because it has been shown that affectively positive odors are represented in different brain subregions than affectively unpleasant odors (Anderson et al, 2003;Rolls et al, 2003).…”

Selective Attention to Affective Value Alters How the Brain Processes Olfactory Stimuli

“…In humans, functional magnetic resonance imaging (fMRI) studies of olfaction have shown activations of the pyriform cortex and the orbitofrontal cortex (Plailly, Radnovich, Sabri, Royet, & Kareken, 2007;Gottfried, Winston, & Dolan, 2006;Li, Luxenberg, Parrish, & Gottfried, 2006;de Araujo, Rolls, Velazco, Margot, & Cayeux, 2005;Small, Gerber, Mak, & Hummel, 2005;Winston, Gottfried, Kilner, & Dolan, 2005;Anderson et al, 2003;Royet, Plailly, Delon-Martin, Kareken, & Segebarth, 2003;Poellinger et al, 2001;Savic, Berglund, Gulyas, & Roland, 2001;Zald & Pardo, 2000;Zatorre, Jones-Gotman, & Rouby, 2000). In particular, it has been shown that activations of the medial orbitofrontal cortex are correlated with the subjective pleasantness of olfactory stimuli, and of the lateral orbitofrontal cortex with unpleasantness, whereas activations of the pyriform cortex are correlated with the intensity but not the pleasantness of olfactory stimuli .…”