Perceiving Smellscapes

We perceive smells as perduring complex entities within a distal array that might be conceived of as smellscapes. However, the philosophical orthodoxy of Odor Theories has been to deny that smells are perceived as having a distal location. Recent challenges have been mounted to Odor Theories’ veracity in handling the timescale of olfactory perception, how it individuates odors as a distal entities, and their claim that olfactory perception is not spatial. The paper does not aim to dispute these criticisms. Rather, what will be shown is that Molecular Structure Theory, a refinement of Odor Theory, can be further developed to handle these challenges. The theory is further refined by focusing on distal perception that requires considering the perceptual object as mereologically complex persisting odor against a background scene conceived of as a smellscape. What will be offered is an expansion of Molecular Structure Theory to account for distal smell perception within natural environments

Odors: from chemical structures to gaseous plumes

We are immersed within an odorous sea of chemical currents that we parse into individual odors with complex structures. Odors have been posited as determined by the structural relation between the molecules that compose the chemical compounds and their interactions with the receptor site. But, naturally occurring smells are parsed from gaseous odor plumes. To give a comprehensive account of the nature of odors the chemosciences must account for these large distributed entities as well. We offer a focused review of what is known about the perception of odor plumes for olfactory navigation and tracking, which we then connect to what is known about the role odorants play as properties of the plume in determining odor identity with respect to odor quality. We end by motivating our central claim that more research needs to be conducted on the role that odorants play within the odor plume in determining odor identity

Smell's puzzling discrepancy: Gifted discrimination, yet pitiful identification

Mind &Language, Volume 35, Issue 1, Page 90-114, February 2020

Active sensing in a dynamic olfactory world

© The Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.This Perspective highlights the shift from the classic picture of olfaction as slow and static to a view in which dynamics play a critical role at many levels of sensing and behavior. Olfaction is now increasingly seen as a “wide-bandwidth temporal sense” (Ackels et al., 2021; Nagel et al., 2015). A parallel transition is occurring in odor-guided robot navigation, where it has been discovered that sensors can access temporal cues useful for navigation (Schmuker et al., 2016). We are only beginning to understand the implications of this paradigm-shift on our view of olfactory and olfactomotor circuits. Below we review insights into the information encoded in turbulent odor plumes and shine light on how animals could access this information. We suggest that a key challenge for olfactory neuroscience is to re-interpret work based on static stimuli in the context of natural odor dynamics and actively exploring animals.Peer reviewedFinal Published versio

An Experimental Biomimetic Platform for Artificial Olfaction

Artificial olfactory systems have been studied for the last two decades mainly from the point of view of the features of olfactory neuron receptor fields. Other fundamental olfaction properties have only been episodically considered in artificial systems. As a result, current artificial olfactory systems are mostly intended as instruments and are of poor benefit for biologists who may need tools to model and test olfactory models. Herewith, we show how a simple experimental approach can be used to account for several phenomena observed in olfaction

Spatial information from the odour environment in mammalian olfaction

The sense of smell is an essential modality for many species, in particular nocturnal and crepuscular mammals, to gather information about their environment. Olfactory cues provide information over a large range of distances, allowing behaviours ranging from simple detection and recognition of objects, to tracking trails and navigating using odour plumes from afar. In this review, we discuss the features of the natural olfactory environment and provide a brief overview of how odour information can be sampled and might be represented and processed by the mammalian olfactory system. Finally, we discuss recent behavioural approaches that address how mammals extract spatial information from the environment in three diferent contexts: odour trail tracking, odour plume tracking and, more general, olfactory-guided navigation. Recent technological developments have seen the spatiotemporal aspect of mammalian olfaction gain signifcant attention, and we discuss both the promising aspects of rapidly developing paradigms and stimulus control technologies as well as their limitations. We conclude that, while still in its beginnings, research on the odour environment ofers an entry point into understanding the mechanisms how mammals extract information about space

Orientation in space using the sense of smell

Several studies reported that respiration interacts with olfactory perception. Therefore, in the pilot study of this experiment series human breathing was investigated during an olfactory experiment. Breathing parameters (respiratory minute volume, respiratory amplitude, and breathing rate) were quantified in response to odor stimulation and olfactory imagery. We provide evidence that respiration changed during smelling and during olfactory imagery in comparison to the baseline condition. In conclusion, olfactory perception and olfactory imagery both have an impact on the human respiratory profile, which is hypothesized to be based on a common underlying mechanism named sniffing. Our findings underline that for certain aspects of olfactory research it may be necessary to control and/or monitor respiration during olfactory stimulation. The human ability to localize odors has been investigated in a limited number of studies, but the findings are contradictory. We hypothesized that this was mainly due to differential effects of olfactory and trigeminal stimulation. Only few substances excite selectively the olfactory system. One of them is hydrogen sulphide (H2S). In contrast, most odorants stimulate both olfactory and trigeminal receptors of the nasal mucosa. The main goal of this study was to test the human ability to localize substances, which excite the olfactory system selectively. For this purpose we performed localization experiment using low and high concentrations of the pure odorant H2S, the olfactory-trigeminal substance isoamyl acetate (IAA), and the trigeminal substance carbon dioxide (CO2). In preparation for the localization study a detection experiment was carried out to ensure that subjects perceived the applied stimuli consciously. The aim of the detection study was to quantify the human sensitivity in response to stimulation with H2S, IAA, and CO2. We tested healthy subjects using an event-related experimental design. The olfactory stimulation was performed using an olfactometer. The results showed that humans are able to detect H2S in low concentration (2 ppm) with moderate sensitivity, and possess a high sensitivity in response to stimulation with 8ppm H2S, 50% v/v CO2, and 17.5% v/v IAA. The localization experiment revealed that subjects can localize H2S neither in low nor in high concentrations. In contrast to that, subjects possess an ability to localize both IAA and CO2 stimuli. These results clearly demonstrate that humans are able to localize odorants which excite the trigeminal system, but they are not able to localize odors that stimulate the olfactory system exclusively, in spite of consciously perceiving the stimuli