Smelling the space around us: Odor pleasantness shifts visuospatial attention in humans (original) (raw)
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Pleasant or Unpleasant: Attentional Modulation of Odor Perception
Chemosensory Perception, 2012
Using positron emission tomography, we investigated whether regional brain activations differ as a function of attending to pleasant versus unpleasant components of odors. There were two experimental (attention to pleasantness and attention to unpleasantness) and one control (baseline) condition. The stimuli presented during the two experimental conditions were exactly the same (three binary mixtures, each consisting of one pleasant and one unpleasant compound), but the affective property to which participants' attention was directed was different: They indicated with a mouse click whether each stimulus contained a pleasant (during attention to pleasantness) or unpleasant (during attention to unpleasantness) odor. During baseline, odorless stimuli were presented, and participants pressed the mouse button randomly after each one. Several brain regions were involved in both types of attention, and these included ventral striatum, right orbitofrontal cortex, and anterior cingulate cortex. Subtle differences were also revealed: Attending to pleasantness was associated preferentially with a sensory/perceptual network (piriform cortex and amygdala), whereas attending to unpleasantness engaged a component of the attentional (right parietal) network. Thus, we delineate neural substrates of attending to olfactory pleasantness and unpleasantness, some of which are common to both and others that are specific to pleasantness or to unpleasantness. Our results suggest that the view of the mesolimbic dopaminergic system as the reward network that responds selectively to positive reinforcers is somewhat limited: Our findings are more in keeping with a view of this set of structures as the salience system of the brain.
Ambient odors modulate visual attentional capture
Neuroscience Letters, 2003
Sudden visual events capture attention involuntarily because they may signal potential threats. Some theoretical accounts consider that the biological significance of these events is established through the limbic structures. Thus, the manipulation of the limbic activity would affect attentional capture. Since these structures are directly linked to the olfactory system, we have tended to modulate their activity with olfactory stimulations. We have examined behavioral performance in a task of attentional capture by luminance under conditions of ambient odors. Our results show that attentional capture is indeed modulated by ambient odors, and that this modulation may depend on the odor's properties.
2013
Crossmodal correspondences between odors and visual stimuli—particularly colors—are well-established in the literature, but there is a paucity of research involving visual shape correspondences. Crossmodal associations between 20 odors (a selection of those commonly found in wine) and visual shape stimuli (“kiki”/“bouba ” forms—Köhler W. 1929. Gestalt psychology. New York: Liveright.) were investigated in a sample of 25 participants (mean age of 21 years). The odors were rated along a form scale anchored by 2 shapes, as well as several descriptive adjective scales. Two of the odors were found to be signifi-cantly associated with an angular shape (lemon and pepper) and two others with a rounded shape (raspberry and vanilla). Principal component analysis indicated that the hedonic value and intensity of odors are important in this crossmodal asso-ciation, with more unpleasant and intense smells associated with more angular forms. These results are discussed in terms of their practical...
Psychonomic Bulletin & Review, 2013
Olfactory experiences represent a domain that is particularly rich in crossmodal associations. Whereas associations between odors and tastes, or other properties of their typical sources such as color or temperature, can be straightforwardly explained by associative learning, other matchings are much harder to explain in these terms, yet surprisingly are shared across individuals: The majority of people, for instance, associate certain odors and auditory features, such as pitch (
Brain Mechanisms for Extracting Spatial Information from Smell
Neuron, 2005
put across nostrils was supported by von Békésy 1 Program in Biophysics (1964), who, in an elegant study, found that differences 2 Program in Bioengineering in odorant concentration or in time of stimulus arrival 3 Helen Wills Neuroscience Institute across the two nostrils enable humans to spatially lo-4 Department of Psychology calize an odorant (1964). University of California, Berkeley To investigate the neural substrates that subserve the Berkeley, California 94720 behavioral mechanism described by von Békésy, we set out to conduct a left versus right odorant localization study within the functional magnetic resonance (fMRI) scanner. The following considerations guided us Summary in the selection of odorants for this task. Odor perception results from the combination of inputs from odor-Forty years ago, von Békésy demonstrated that the ant transduction at a number of different nerves (Bojspatial source of an odorant is determined by comsen-Moller, 1975). Whereas high concentrations of paring input across nostrils, but it is unknown how most known odorants will excite the trigeminal and olthis comparison is effected in the brain. To address factory nerves ("trigeminal odorants"), a very small this, we delivered odorants to the left or right of the number of odorants will excite the olfactory nerve only nose, and contrasted olfactory left versus right local-("pure olfactants"). Although these nerve pathways are ization with olfactory identification during brain imlinked at both peripheral (Bouvet et al., 1987; Schaefer aging. We found nostril-specific responses in primary et al., 2002) and central (Macrides and Chorover, 1972; olfactory cortex that were predictive of the accuracy Stone and Rebert, 1970; Stone et al., 1968) aspects of the of left versus right localization, thus providing a neuolfactory system, they nevertheless induce dissociable ral substrate for the behavior described by von neural responses (Hummel et al., 1992; Savic, 2002; Savic Békésy. Additionally, left versus right localization et al., 2002), and more pertinently, may contribute difpreferentially engaged a portion of the superior temferently to odorant localization. Most attempts to replicate poral gyrus previously implicated in visual and audithe result obtained by von Békésy have suggested that tory localization, suggesting that localization informaspatial localization of an odorant is possible only when tion extracted from smell was then processed in a the odorant is trigeminal (Kobal et al., 1989; Radil and convergent brain system for spatial representation of Wysocki, 1998; Schneider and Schmidt, 1967), although multisensory inputs. some have not ruled out pure olfactory localization under some circumstances (Schneider and Schmidt, 1967). In
The structure of human olfactory space
2009
We analyze the psychophysical responses of human observers to an ensemble of monomolecular odorants. Each odorant is characterized by a set of 146 perceptual descriptors obtained from a database of odor character profiles. Each odorant is therefore represented by a point in highly multidimensional sensory space. In this work we study the arrangement of odorants in this perceptual space. We argue that odorants densely sample a two-dimensional curved surface embedded in the multidimensional sensory space. This surface can account for more than half of the variance of the psychophysical data. We also show that only 12% of experimental variance cannot be explained by curved surfaces of substantially small dimensionality (<10). We suggest that these curved manifolds represent the relevant spaces sampled by the human olfactory system, thereby providing surrogates for olfactory sensory space. For the case of 2D approximation, we relate the two parameters on the curved surface to the physicochemical parameters of odorant molecules. We show that one of the dimensions is related to eigenvalues of molecules' connectivity matrix, while the other is correlated with measures of molecules' polarity. We discuss the behavioral significance of these findings.
Odor lateralization and spatial localization: Null effects of blindness
Attention, Perception, & Psychophysics
People can navigate through an environment using different sensory information, including olfactory cues. Correct intranasal localization and external location of odors can be learned, and some people are able to lateralize olfactory stimuli above chance, which raises the question: What determines the spectrum of olfactory localization abilities. Here, we explored whether odor lateralization and localization abilities are increased in the course of sensory compensation. In a series of studies, we combined two different aspects of odor localization. Study 1 compared abilities of 69 blind people (M age = 41 ± 1.6 years; 32 females) and 45 sighted controls (M age = 38.3 ± 2.1 years; 25 females) to correctly lateralize eucalyptol, an odorant with a strong trigeminal component, presented to either nostril. Studies 2 and 3 involved a more ecologically valid task, namely spatial localization of olfactory stimuli. In Study 2, 13 blind individuals (M age = 28.5 ± 3.5 years; seven females) and 16 sighted controls (M age = 34.9 ± 3.2 years; ten females) tried to localize a single odorant, while in Study 3, 97 blind individuals (M age = 43.1 ± .5 years; 48 females) and 47 sighted controls (M age = 38.7 ± .7 years; 27 females) attempted to localize a single target odor in an experimental olfactory space comprising four different odorants. Blind and sighted subjects did not differ in their abilities to lateralize and to localize odors, and their performance across all tasks suggests that odor lateralization and localization are important for navigation in an environment regardless of visual status.
Spatial aspects of olfactory experience
Canadian Journal of Philosophy, 2019
Several theorists argue that one does not experience something as being at or coming from a distance or direction in olfaction. In contrast to this, I suggest that there can be a variety of spatial aspects of both synchronic and diachronic olfactory experiences, including spatial distance and direction. I emphasise, however, that these are not aspects of every olfactory experience. Thus, I suggest renouncing the widespread assumption there is a uniform account of the nature, including the spatial nature, of what is experienced in olfactory experience.
Olfactory Discrimination: When Vision Matters
Chemical Senses, 2008
Many previous studies have attempted to investigate the effect of visual cues on olfactory perception in humans. The majority of this research has only looked at the modulatory effect of color, which has typically been explained in terms of multisensory perceptual interactions. However, such crossmodal effects may equally well relate to interactions taking place at a higher level of information processing as well. In fact, it is well-known that semantic knowledge can have a substantial effect on people's olfactory perception. In the present study, we therefore investigated the influence of visual cues, consisting of color patches and/or shapes, on people's olfactory discrimination performance. Participants had to make speeded odor discrimination responses (lemon vs. strawberry) while viewing a red or yellow color patch, an outline drawing of a strawberry or lemon, or a combination of these color and shape cues. Even though participants were instructed to ignore the visual stimuli, our results demonstrate that the accuracy of their odor discrimination responses was influenced by visual distractors. This result shows that both color and shape information are taken into account during speeded olfactory discrimination, even when such information is completely task irrelevant, hinting at the automaticity of such higher level visual-olfactory crossmodal interactions.