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

Olfaction and gustation in blindness: a state of the art of the literature

To date, there are quite a few studies assessing olfaction and gustation in blindness, with great variability in sample size, participants' age, blindness onset and smell and taste evaluation methods. Indeed, the evaluation of olfactory and gustatory performance can differ depending on several factors, including cultural differences. Therefore, here we analysed through a narrative review, all the works reporting a smell and taste assessment in blind individuals during the last 130 years, trying to summarize and address the knowledge in this field

Measurement of BOLD changes due to cued eye-closure and stopping during a continuous visuomotor task via model-based and model-free approaches

As a precursor for investigation of changes in neural activity underlying lapses of responsiveness, we set up a system to simultaneously record functional magnetic resonance imaging (fMRI), eye-video, EOG, and continuous visuomotor response inside an MRI scanner. The BOLD fMRI signal was acquired during a novel 2-D tracking task in which participants (10 males, 10 females) were cued to either briefly stop tracking and close their eyes (Stop Close) or to briefly stop tracking (Stop) only. The onset and duration of eye-closure and stopping were identified post hoc from eye-video, EOG, and visuomotor response. fMRI data were analyzed using a general linear model (GLM) and tensorial independent component analysis (TICA). The GLM-based analysis identified predominantly increased blood oxygenation level dependent (BOLD) activity during eye-closure and stopping in multisensory areas, sensory-motor integration areas, and default-mode regions. Stopping during tracking elicited increased activity in visual processing areas, sensory-motor integration areas, and premotor areas. TICA separated the spatio-temporal pattern of activity into multiple task-related networks including the 1) occipito-medial frontal eye-movement network, 2) sensory areas, 3) left-lateralized visuomotor network, and 4) fronto-parietal visuomotor network, which were modulated differently by Stop Close and Stop. The results demonstrate the merits of using simultaneous fMRI, behavioral, and physiological recordings to investigate the mechanisms underlying complex human behaviors in the human brain. Furthermore, knowledge of widespread modulations in brain activity due to voluntary eye-closure or stopping during a continuous visuomotor task is important for studies of the brain mechanisms underlying involuntary behaviors, such as microsleeps and attention lapses, which are often accompanied by brief eye-closure and/or response failures

The Effect of Eye Closure on Empathic Accuracy and Motor Mimicry

Two experiments were conducted to test the hypothesis if eye closure facilitates bottom-up processing, then empathic accuracy in emotional contagion and the frequency of draws in paperrock-scissors would increase. Participants (study 1: N = 94, study 2: N = 84) were asked to pair with partners and report how much they (themselves and partners) currently felt lonely, hungry, and tired on a 7-point scale with eyes-closed or eyes-open conditions. After that, they played rock-paper-scissors twelve times. Results showed that the frequency of draws and the score of empathic accuracy did not increased in eyes-closed condition, however, some of theresults suggested a possibility of eye closure effect. The relevance of eye closure, empathic accuracy, and motor mimicry were discussed.もし閉眼がボトムアップ処理を促進するなら，目を閉じることで，共感の正確性が上がり，じゃんけんで引き分けやすくなるだろう，という仮説を検証するため，2つの実験を実施した。大学生の参加者（研究1 : N＝94, 研究2 : N＝84）が二人組を作り，閉眼または開眼で，現在の孤独・空腹・疲労の程度を，お互いに7段階で評定した。その後，じゃんけんを12回行った。閉眼は共感の正確性や動作の模倣を直接促さなかったが，一部の結果はその可能性を示唆した。閉眼・共感の正確性・動作模倣のモデルについて考察した

Development of a functional MRI Olfactory Protocol

Many people can spend a few days with an acute form of sinusitis, a stuffy nose, or sinus congestion that inhibits their ability to smell, but there are fourteen million Americans over the age of fifty that suffer from some form of chronic olfactory dysfunction. Some neurological disorders such as Parkinson\u27s disease and Alzheimer\u27s disease have demonstrated that olfactory dysfunction is a frequent and early sign. While these diseases have no known cure, there are medicines that exist to slow the progression of such debilitating illnesses. By identifying such diseases in their early stages, we can improve the quality of life for millions of people throughout the world. This research project will begin to open the doors for more investigation into the relationship of olfaction and Parkinson\u27s disease, Alzheimer\u27s disease, and even epilepsy by the development of an fMRI olfactory stimulation protocol. This protocol successfully identified the olfactory regions of the brain of normal patients

Systemic physiology augmented functional near-infrared spectroscopy hyperscanning: a first evaluation investigating entrainment of spontaneous activity of brain and body physiology between subjects.

Significance: Functional near-infrared spectroscopy (fNIRS) enables measuring the brain activity of two subjects while they interact, i.e., the hyperscanning approach. Aim: In our exploratory study, we extended classical fNIRS hyperscanning by adding systemic physiological measures to obtain systemic physiology augmented fNIRS (SPA-fNIRS) hyperscanning while blocking and not blocking the visual communication between the subjects. This approach enables access brain-to-brain, brain-to-body, and body-to-body coupling between the subjects simultaneously. Approach: Twenty-four pairs of subjects participated in the experiment. The paradigm consisted of two subjects that sat in front of each other and had their eyes closed for 10 min, followed by a phase of 10 min where they made eye contact. Brain and body activity was measured continuously by SPA-fNIRS. Results: Our study shows that making eye contact for a prolonged time causes significant changes in brain-to-brain, brain-to-body, and body-to-body coupling, indicating that eye contact is followed by entrainment of the physiology between subjects. Subjects that knew each other generally showed a larger trend to change between the two conditions. Conclusions: The main point of this study is to introduce a new framework to investigate brain-to-brain, body-to-body, and brain-to-body coupling through a simple social experimental paradigm. The study revealed that eye contact leads to significant synchronization of spontaneous activity of the brain and body physiology. Our study is the first that employed the SPA-fNIRS approach and showed its usefulness to investigate complex interpersonal physiological changes

Zentrale Verarbeitung multimodaler sensorischer Reize nach Stimulation der Nasenschleimhaut mit Nikotin

Zum heutigen Stand der Forschung gibt es, außer der vorliegenden Arbeit, keine funktionellen Kernspinstudien über kortikale Aktivierungen, welche durch Effekte des multimodalen Stimulus Nikotin auf das olfaktorische und das trigeminale System hervorgerufen werden. Appliziert man Nikotindampf in niedrigen Konzentrationen auf die nasale Mukosa, so ruft es Geruchsempfindungen, die durch das olfaktorische System vermittelt werden, hervor. In höheren Konzentrationen ruft Nikotin zusätzlich ein Brennen oder Stechen in der Nase hervor, welches durch das trigeminale System vermittelt wird. Das Ziel der vorliegenden Arbeit war, die Hirnaktivierungen nach intranasaler Stimulation von S(-)-Nikotin in niedrigen, olfaktorisch leicht überschwelligen versus hohen, trigeminal leicht überschwelligen Konzentrationen zu vergleichen. Zuerst wurden die individuellen Geruchs- und Schmerzschwellen von Nikotin von jeweils 30 gesunden Gelegenheitsrauchern mittels PC-kontrolliertem Olfaktometer bestimmt. Danach wurden funktionelle Kernspinuntersuchungen mit einem 1,5 Tesla Magnetresonanztomographen während der Applikation von intranasalen Nikotinreizen in olfaktorisch und trigeminal leicht überschwelligen Konzentrationen durchgeführt. Nach den Bildgebungsexperimenten nahm ein Teil der Probanden an einem weiteren Experiment teil. Während dieses Experiments sollten die Probanden die Intensität der olfaktorischen und trigeminalen Wahrnehmung während intranasaler Nikotinstimulation außerhalb des Magnetresonanztomographen bewerten. Dabei wurden die gleichen Stimulationsparadigmen verwendet wie während der Bildgebungsexperimente. Obwohl die subjektive Wahrnehmung von Nikotindampf in niedrigen und hohen Konzentrationen sich deutlich voneinander unterschied, konnten Aktivierungen in nahezu gleichen Hirnarealen in beiden Experimenten gefunden werden. Diese Hirnareale entsprachen Arealen, von denen bekannt ist, dass sie für die olfaktorische Informationsverarbeitung zuständig sind, aber auch Arealen, die spezifisch für die Verarbeitung von schmerzhaften Reizen sind. Die Ergebnisse zeigen, dass sowohl das olfaktorische, als auch das trigeminale System während chemosensorischer Wahrnehmung von Nikotindampf aktiviert werden und dass es nicht möglich ist, olfaktorische von trigeminalen Effekten zu trennen, indem man die Stimuluskonzentration variiert. Die Aktivierungen von olfaktorischen und trigeminalen Arealen nach chemosensorischer Stimulation mit verschiedenen Nikotinkonzentrationen sind weitgehend unabhängig von der wahrgenommenen Intensität der Stimuli.Besides the present study no neuroimaging data are available on cortical activations induced by the effects of the multimodal stimulus nicotine on the olfactory or the trigeminal system. Applied to the nasal mucosa in low concentrations, nicotine vapor evokes odorous sensations (mediated by the olfactory system). At higher concentrations, nicotine vapor produces burning and stinging sensations in the nose (mediated by the trigeminal system). The aim of this study was to compare brain areas activated by intranasal stimulation with S(-)-nicotine vapor in low versus high concentrations using functional magnetic resonance imaging (fMRI). Olfactory detection thresholds and sensory irritation thresholds for nicotine vapor were determined in thirty healthy occasional smokers respectively using a computer-controlled air-dilution olfactometer. Following this, functional magnetic resonance images were acquired using a 1.5T MR scanner with application of concentrations of nicotine vapor just above the individual’s olfactory detection threshold and just above the individual’s sensory irritation threshold. After the scanning sessions a part of the subjects participated in a further session. They were lying outside the MR scanner and were instructed to evaluate the intensity of the olfactory and the trigeminal percept during the stimulation paradigms used before. Although perceptions of nicotine vapor in low and high concentrations completely differed, activations in basically the same brain areas were found in both fMRI experiments. These brain areas correspond to areas known to be activated following olfactory stimulation of the nasal mucosa, as well as areas specific to processing of painful stimuli. These findings indicate that the olfactory and trigeminal systems are both activated during chemosensory perception of nicotine vapor and it is not possible to separate olfactory from trigeminal effects by varying the concentration of the applied nicotine vapor. Brain activation of olfactory and trigeminal areas related to chemosensory stimulation with different concentrations of nicotine vapor is independent of perceptual strength

Optimization of Functional MRI methods for olfactory interventional studies at 3T

Functional MRI technique is vital in investigating the effect of an intervention on cortical activation in normal and patient population. In many such investigations, block stimulation paradigms are still the preferred method of inducing brain activation during functional imaging sessions because of the high BOLD response, ease in implementation and subject compliance especially in patient population. However, effect of an intervention can be validly interpreted only after reproducibility of a detectable BOLD response evoked by the stimulation paradigm is first verified in the absence of the intervention. Detecting a large BOLD response that is also reproducible is a difficult task particularly in olfactory Functional MRI studies due to the factors such as (a) susceptibility-induced signal loss in olfactory related brain areas and (b) desensitization to odors due to prolonged odor stimulation, which is typical when block paradigms are used. Therefore, when block paradigms are used in olfactory interventional Functional MRI studies, the effect of the intervention may not be easily interpretable due to the factors mentioned above. The first task of this thesis was to select a block stimulation paradigm that would produce a large and reproducible BOLD response. It was hypothesized that a BOLD response of this nature could be produced if within-block and across-session desensitization could be minimized and further, that desensitization could be minimized by reducing the amount of odor by pulsing the odor stimulus within a block instead of providing a continuous odor throughout the block duration. Once the best paradigm was selected, the second task of the thesis was to select the best model for use in general linear model (GLM) analysis of the functional data, so that robust activation is detected in olfactory related brain areas. Finally, the third task was to apply the paradigm and model that were selected as the best among the ones tested in this thesis, to an olfactory interventional Functional MRI study investigating the effect of food (bananas) eaten to satiety on the brain activation to the odor related to that food. The methods used in this thesis to ensure valid interpretation of an interventional effect, can serve as a template for the experimental design of future interventional Functional MRI studies

Der Einfluss von trauriger Stimmungsinduktion auf die Riech- und Schmeckschwellen gesunder Frauen

Der Geruch- und der Geschmacksinn sind eng mit Gefühlen verbunden und stehen unter dem Einfluss unserer Stimmung. Depressive Patienten besitzen eine verminderte olfaktorische Sensibilität. Gleichsam konnte für den Geschmackssinn eine veränderte Wahrnehmung bei Depressiven dargestellt werden. Aber auch gesunde Menschen sind in ihrem Riechvermögen durch eine traurige Stimmung, welche experimentell induziert wird, beeinflussbar. Wir stellten in dieser Arbeit die Hypothese auf, dass eine traurige Stimmung sowohl die olfaktorische als auch die gustatorische Sensibilität vermindern kann. Dazu induzierten wir mithilfe der Stimmungsinduktion nach Velten eine traurige und zum Vergleich neutrale Stimmung bei gesunden Probanden. Anhand von Wahrnehmungsschwellentestungen untersuchten wir die Geschmacks- und Geruchsperzeption vor und nach der induzierten Stimmung. Im Gegensatz zu unserer aufgestellten Hypothese verringerte sich nicht die olfaktorische Sensibilität der Probanden, die die traurige Stimmungsinduktion erhielten. Vielmehr konnten wir eine signifikante Abnahme der Wahrnehmungsschwellen für die beiden Geruchsstoffe n-Butanol und Phenylethylalkohol im traurigen Affekt darstellen, welche eine Zunahme der Geruchsempfindung bedeutet. Für die Perzeption des süßen und sauren Geschmacksstoffes ließ sich keine signifikante Änderung nach der traurigen Stimmungsinduktion verzeichnen. Unsere Ergebnisse stehen im Widerspruch zu den Untersuchungen, die mit depressiven Patienten durchgeführt wurden. Wir nehmen an, dass eine induzierte traurige Stimmung einen anderen Einfluss auf die Geruchs- und Geschmackswahrnehmung hat als eine Depression. Auf welche Art und Weise eine traurige Stimmung jedoch die Perzeption beeinflusst, kann nur spekuliert werden. Vermutlich kommt veränderten Aufmerksamkeitsaspekten bei einer induzierten traurigen Stimmung eine wesentliche Bedeutung zu