Academic literature on the topic 'Olfactory search'

AbstractStriped skunks (Mephitis mephitis) which had been raised in captivity can increase their reaction distance to the smell of a given food. This reaction distance decreases after they find other types of foods, using either sound or smell. This decrease could be a result of skunks increasing preference for specific food, or shifting attention onto the smell of specific food. However, other experiments showed that skunks do not change prey preference. Therefore the decrease in reaction distance is likely due to skunks shifting attention to the smell of specific food. I suggest that this is the olfactory analogue to visual search images-i.e. olfactory search images.

Introduction: The olfactory system in chronic animal experiments is studied according to the records of bioelectric activity recorded with microelectrode arrays located on the dorsal surface of the olfactory bulb. It is believed that the response of the olfactory bulb bioelectric activity to the odorant presentation is associated with fluctuations synchronized by respiration and belonging to the range of so-called gamma rhythms. Purpose: To develop a method of automatic search for time boundaries of odor-induced gamma rhythm patterns in the bioelectric activity of an olfactory bulb. Results: The complexity of automatic search for odor-induced patterns are due to masking them by spontaneous oscillations of gamma rhythms unrelated to the olfactory system activity. Besides, the modal frequency of the patterns is a priori unknown and changes dynamically during an experiment on an anesthetized animal. The Hausdorff distance is used as a cost function of the search. In order to increase its sensitivity, an adaptive band-pass filter was synthesized based on a multichannel singular spectrum analysis. Its passband in the analyzed time sample corresponds best to the spectrum of the required patterns. The results of experiments on rats are presented. The use of band-pass filters based on the Fourier transform with parameters unchanged during the experiment due to the non-stationary nature of the frequency characteristics of the desired patterns does not ensure their effective search. In particular, when using the Butterworth band-pass filter in the search algorithm, significant errors were observed in determining the time boundaries of the epochs of patterns, and omissions of patterns. But the use of a synthesized adaptive band-pass filter provided reliable automatic search for patterns and determination of their time boundaries with a high accuracy. Algorithm failures in this case were observed only in rat motion artifacts. Practical relevance: The developed method extends the existing tools used to study the olfactory system of a living organism.

Thesis (Ph.D)--Biology, Georgia Institute of Technology, 2009.
Committee Chair: Weissburg, Marc; Committee Member: Hay, Mark; Committee Member: Kubanek, Julia; Committee Member: Webster, Donald; Committee Member: Yen, Jeannette. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Tese de doutoramento em Engenharia Electrotécnica e de Computadores, no ramo de especialização em Automação e Robótica, sob orientação do Professor Lino José Forte Marques, apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra.
Searching for olfactory targets with mobile robots has received much attention in the recent years due to its applications in chemical leak detection, environmental monitoring, pollution monitoring, inspection of landfills, and search and rescue operations. Some of these tasks are done in scenarios extremely dangerous for humans, making it more desirable to use robots instead. The use of autonomous robots to assist such tasks reduces the risks involved in these operations. This thesis aims to address the problem of searching for olfactory targets with a group of mobile robots. A group of robots with on-board sensors can actually form a mobile sensor network, so they can cover larger area in a shorter time and they show better performance in several scenarios (e.g., in the face of noisy and large environments) in comparison to a single robot. Two types of robotic groups are considered in this thesis; “multi-robot systems” and “swarm robotic systems.” For each of these systems a certain objective is defined to address several challenges in robotic olfactory search. “Olfactory search and exploration with multiple robots in structured unknown environments” and “swarm robotics olfactory search in unstructured unknown environments” are the two defined objectives of this thesis. In both objectives, the problem of “odor plume finding” that is the first step to localize odor sources is considered as the main problem. To fulfill the first objective, this thesis presents a multi-robot olfactory search and exploration method designed for structured environments. The method is a decentralized frontier based algorithm enhanced by a cost=utility evaluation function that considers the gas cues (odor concentration and airflow) at each frontier which makes the robots to try to find the odor sources as fast as possible. Several challenges namely “task sharing and cooperation”, “localization and multi-robot mapping”, “programming and processing” in addition to “olfactory search challenges” are addressed. The proposed method is evaluated in simulations and in small-scaled realistic structured environments. The results of real world experiments confirm the e ect of gas cues on the behavior of the robots and show that using the proposed algorithm, robots firstly explore the areas with higher probability of existence of odor sources. Simulation results show that having more robots is more advantageous in a complex environment than in a simple environment. We address the second objective, “swarm robotics olfactory search in unstructured unknown environments”, through an analytical optimization approach. Defining single and multiple (stationary and mobile) gas sensors coverage and finding the optimal configuration of N mobile sensors in di erent environmental conditions are among the main novelties of this thesis. We found that the topology of optimal solutions is in the form of line configuration, with equal distance between each pair of neighboring sensors. Regardless of number of sensors, the optimal distance between neighboring pairs depends on the wind speed. A mathematical function that can accurately estimate the optimal distances based on the wind speed was computed by nonlinear regression estimation. Moreover, based on the results of optimizations, we present and design a set of wind-biased virtual attractive/repulsive control forces for the swarm robots such that their emergent behavior converges to the optimal formations. The optimization results were validated and evaluated by experiments in realistic environments. Finally, this dissertation proposes a method for “swarm robotics odor plume tracking and source declaration.” We present the implementation of the proposed method in simulations and provide some preliminary results of its validations and discuss the future works of this work.
A procura de alvos olfactivos com recurso a robˆos m´oveis tem recebido bastante atenc¸ ˜ao por parte da comunidade cient´ıfica nos ´ultimos anos. Isto deve-se, em parte `as poss´ıveis aplicac¸ ˜oes em cen´arios tais como a detecc¸ ˜ao de fugas qu´ımicas, monitorizac¸ ˜ao ambiental, monitorizac¸ ˜ao de agentes poluentes, inspecc¸ ˜ao de aterros e operac¸ ˜oes de busca e salvamento. Algumas destas tarefas s˜ao realizadas em ambientes extremamente perigosos para os humanos, o que torna o recurso a robˆos ainda mais apelativo. A assistˆencia de robˆos aut´onomos em tarefas como estas reduz o risco envolvido para os humanos nestas operac¸ ˜oes. Esta tese tem como objectivo ir de encontro ao problema da busca de alvos olfactivos atrav´es do uso de um grupo de robˆos m´oveis, equipados com sensores de g´as. Este grupo pode formar uma rede de sensores m´ovel, permitindo a cobertura de ´areas mais extensas num per´ıodo de tempo mais curto, o que se traduz num melhor desempenho em diversos ambientes (e.g., na presenc¸a de ambientes ruidosos e amplos) quando comparado com uma soluc¸ ˜ao que utiliza apenas um robˆo. Nesta tese s˜ao considerados dois tipos de grupos de robˆos: “sistemas multirob ˆo” e “sistemas de enxames de robˆos”. Para cada um destes sistemas, define-se um objectivo de forma a ir ao encontro de v´arios desafios no ˆambito da busca olfactiva com robˆos m´oveis. “Busca olfactiva e explorac¸ ˜ao com recurso a m´ultiplos robˆos em ambientes desconhecidos e estruturados” e “busca olfactiva com recurso a enxames de robˆos em ambientes desconhecidos e n˜ao-estruturados” s˜ao os dois objectivos principais desta tese. Em ambos os objectivos o problema de “encontrar a pluma de odor”, o primeiro passo na localizac¸ ˜ao de fontes de odor, ´e considerado como o problema principal. Para cumprir o primeiro objectivo, esta tese apresenta um m´etodo multi-robˆo de procura olfactiva desenvolvido para ambientes estruturados. Este consiste num algoritmo de fronteira, descentralizado, optimizado por uma func¸ ˜ao de avaliac¸ ˜ao de custo/utilidade que considera pistas de odor (concentrac¸ ˜ao de odor e informac¸ ˜ao de correntes de ar) em cada fronteira, o que leva a que o robˆo tente encontrar fontes de odor o mais depressa poss´ıvel. Para al´em do desafio da “procura olfactiva”, v´arios desafios tais como a “cooperac¸ ˜ao e partilha de tarefas”, “localizac¸ ˜ao e mapeamento multi-robot” e “programac¸ ˜ao e processamento” foram abordados. O m´etodo proposto foi avaliado em simulac¸ ˜oes e num ambiente estruturado real de pequena escala. Os resultados das experiˆencias reais confirmam o efeito que as pistas de odor exercem no comportamento dos robˆos e mostram que ao utilizar o algoritmo proposto, os robˆos exploram primeiro as ´areas com maior probabilidade de existˆencia de fontes de odor. Os resultados das simulac¸ ˜oes confirmam a vantagem da utilizac¸ ˜ao de mais robˆos em ambientes mais complexos. O segundo objectivo, “busca olfactiva com recurso a enxames de robˆos em ambientes desconhecidos e n˜ao-estruturados”, ´e abordado atrav´es de um algoritmo de optimizac¸ ˜ao anal´ıtico. Definindo uma cobertura singular e m´ultipla (fixa e m´ovel) para os sensores de g´as, encontrou-se a configurac¸ ˜ao ´optima para N sensores m´oveis em diferentes ambientes, uma das principais contribuic¸ ˜oes desta tese. Descobriu-se que a topologia ´optima consiste numa configurac¸ ˜ao em linha, com os sensores equidistantes. Independentemente do n´umero de sensores, a distˆancia ´optima entre pares de sensores vizinhos depende da velocidade do vento. calculou-se uma func¸ ˜ao matem´atica capaz de estimar de forma ´optima a distˆancia entre pares vizinhos de sensores, com base na velocidade do vento atrav´es de estimac¸ ˜ao por regress˜ao n˜ao-linear. Com base nos resultados das optimizac¸ ˜oes, desenvolveram-se e apresentaram-se um conjunto de forc¸as de controlo de atracc¸ ˜ao/repuls˜ao para enxames de robots influenciadas pelo vento. O comportamento emergente, converge para as formac¸ ˜oes ´optimas. Os resultados das optimizac¸ ˜oes foram validados e avaliados por experiˆencias em ambientes realistas. Finalmente esta dissertac¸ ˜ao prop˜oe um m´etodo para o “seguimento de plumas de odor e declarac¸ ˜ao de fontes de odor com exames de robˆos”. Apresenta-se a implementac¸ ˜ao do m´etodo proposto em simulac¸ ˜oes e apresentam-se alguns resultados preliminares da sua validac¸ ˜ao bem como a discuss˜ao de trabalho futuro nesta ´area.

Part I of the thesis describes the olfactory searching and scanning behaviors of rats in a wind tunnel, and a detailed movement analysis of terrestrial arthropod olfactory scanning behavior. Olfactory scanning behaviors in rats may be a behavioral correlate to hippocampal place cell activity.

Part II focuses on the organization of olfactory perception, what it suggests about a natural order for chemicals in the environment, and what this in tum suggests about the organization of the olfactory system. A model of odor quality space (analogous to the "color wheel") is presented. This model defines relationships between odor qualities perceived by human subjects based on a quantitative similarity measure. Compounds containing Carbon, Nitrogen, or Sulfur elicit odors that are contiguous in this odor representation, which thus allows one to predict the broad class of odor qualities a compound is likely to elicit. Based on these findings, a natural organization for olfactory stimuli is hypothesized: the order provided by the metabolic process. This hypothesis is tested by comparing compounds that are structurally similar, perceptually similar, and metabolically similar in a psychophysical cross-adaptation paradigm. Metabolically similar compounds consistently evoked shifts in odor quality and intensity under cross-adaptation, while compounds that were structurally similar or perceptually similar did not. This suggests that the olfactory system may process metabolically similar compounds using the same neural pathways, and that metabolic similarity may be the fundamental metric about which olfactory processing is organized. In other words, the olfactory system may be organized around a biological basis.

The idea of a biological basis for olfactory perception represents a shift in how olfaction is understood. The biological view has predictive power while the current chemical view does not, and the biological view provides explanations for some of the most basic questions in olfaction, that are unanswered in the chemical view. Existing data do not disprove a biological view, and are consistent with basic hypotheses that arise from this viewpoint.

Abstract The evolution of the nervous system enabled better guidance for movements essential for life. Initially the guidance was provided by the memory of olfactory clues. The proposal is made that activation of such memory generated a basic consciousness.

Abstract During evolution of the mammalian hippocampus place cells may have increased their range of activity by coding for ‘what’ regardless of ‘where,’ thereby creating semantic memory. Is the hippocampus continually creating ever-changing spatial maps? Are the arrays of grid cells in the entorhinal cortex related to the map of odour-specific glomeruli in the olfactory bulb?

Abstract In 19th-century Paris, Paul Broca recognizes a ‘great limbic lobe’ at the base of each cerebral hemisphere in mammals. Subsequently, Charles Judson Herrick points out prominence of the olfactory system in ‘lower’ animals, with other sensory systems occupying more and more of the cortex during evolution of the brain. Paul MacLean proposes that the mammalian brain comprises three functional entities—the ‘triune brain.’

This chapter discusses the sense of smell of animals. One way of acquiring information from chemicals in the world is through smell. Just as with the other senses, smell is used for many things, from finding food, judging relatedness and kin, locating and assessing potential mates, marking and defending territories, and much more. The chapter focuses first on ants, which are quite representative of how olfaction broadly works in nature. Located on the antennae of many insects are the main sensory receptors for encoding aspects of the world, from temperature and humidity through to pressure. In insect olfaction, the organs in which the receptors are housed are the olfactory sensilla. Meanwhile, the sense of smell of dogs has contributed to their long working relationship with humans, from help in hunting to search and rescue. After being domesticated for so long, dogs are also extremely good at reading humans, and this has clearly been a valuable trait for breeders in producing a variety of working and companion dogs. Finally, the chapter looks at the eastern American mole, which is one of the several mammals that has been shown to smell in stereo. The findings in the stereo mole essentially parallel some of the features of sound detection, rather like the way in which owls zero in on hidden prey based on the noises they make.

Introduction: Parkinson’s disease is a progressive neurodegenerative disease that affects millions of people worldwide. Although Parkinson’s disease has traditionally been described as a disorder of the motor system, it is now recognized as a complex disease with several clinical features that include neuropsychiatric and non-motor manifestations. Studies show that 97% of patients with Parkinson’s disease report non-motor symptoms, in addition to motor symptoms, and some non-motor characteristics may appear before classic motor signs. Objectives: To list the main non-motor clinical manifestations of Parkinson’s disease and analyze its importance in establishing an accurate and early clinical diagnosis. Methods: This is an integrative review, carried out based on the search of scientific publications indexed in the datebase MEDLINE via PubMed, Lilacs and SciELO. At the end of the searches, 66 publications met the eligibility criteria and were selected to compose the study. Results: Within the non-motor clinical manifestations, there may be present: cognitive dysfunction and dementia, psychosis and hallucinations, mood disorders, sleep disorders, fatigue, autonomic dysfunction, olfactory dysfunction, gastrointestinal dysfunction, pain, sensory disorders and dermatological manifestations. Of these, olfactory dysfunction, constipation, depression and sleep disorders stand out because they often precede the motor symptoms of Parkinson’s disease. Conclusion: In this perspective, it is up to the general practitioner and the neurologist or geriatrician to carry out, whenever possible, screening tests to identify early changes that may precede Parkinson’s disease, guaranteeing patients an early multiprofessional treatment and consequently a better prognosis in the course of the disease.

Background: Clinical practice throughout the pandemic has generated a debate about the existence of neurotropism and the neuropathogenic capacity of the new coronavirus. Medical professionals have noted that there is a wide spectrum of neurological manifestations associated with SARS-CoV-2 infections; from hyposmia to encephalopathy. The interaction of the viral protein spike (S) with the ACE2 gene present in endothelial and nerve cells and the cytokine storm triggered by COVID-19 are explanatory bases for a series of mechanisms proposed in recent literature. Objectives: To establish a direct connection, or not, between neurological manifestations and SARS-CoV-2 infection. Design and setting: Analysis of the current literature present in medical databases. Methods: To select the studies, the Medline (Pubmed), LILACS and SciELO databases were used with the keywords “neurology” and “covid” and “mechanism”. The search period for the articles covered the last 10 months (since June 2020). The selection and design criteria of the studies were descriptive, crosssectional, cohort, case report and randomized clinical study. Results: Thirty-eight articles with potential for inclusion were retrieved, but only seventeen of them declared no conflict of interest and answered the inclusion criteria and the guiding question, which consisted of assessing the association between neurological disorders and COVID-19. Conclusion: Eight studies defend the indirect invasion, due to the imaging exams presenting an olfactory bulb without any alteration. Through infection of the endothelial cells, vascular alterations and wear of the BBB by the cytokine storm. In parallel, the other nine studies advocate direct invasion, where the virus infects the olfactory bulb and reaches the rhinencephalon and midbrain through the axons, generating, for example, the lack of symptoms in the so-called happy hypoxia of the coronavirus. Neuroinvasion in COVID-19 is still unclear, but hypotheses show 2 possible pathways for the virus to access the CNS: hematogenous and retrograde neuronal pathways. To elucidate these pathogenic pathways, larger and more systematic studies will be needed.