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

Measuring the World: Olfaction as a Process Model of Perception

How much does stimulus input shape perception? The common-sense view is that our perceptions are representations of objects and their features and that the stimulus structures the perceptual object. The problem for this view concerns perceptual biases as responsible for distortions and the subjectivity of perceptual experience. These biases are increasingly studied as constitutive factors of brain processes in recent neuroscience. In neural network models the brain is said to cope with the plethora of sensory information by predicting stimulus regularities on the basis of previous experiences. Drawing on this development, this chapter analyses perceptions as processes. Looking at olfaction as a model system, it argues for the need to abandon a stimulus-centred perspective, where smells are thought of as stable percepts, computationally linked to external objects such as odorous molecules. Perception here is presented as a measure of changing signal ratios in an environment informed by expectancy effects from top-down processes

Interactions between cardiac activity and conscious somatosensory perception

Fluctuations in the heart's activity can modulate the access of external stimuli to consciousness. The link between perceptual awareness and cardiac signals has been investigated mainly in the visual and auditory domain. Here, we investigated whether the phase of the cardiac cycle and the prestimulus heart rate influence conscious somatosensory perception. We also tested how conscious detection of somatosensory stimuli affects the heart rate. Electrocardiograms (ECG) of 33 healthy volunteers were recorded while applying near‐threshold electrical pulses at a fixed intensity to the left index finger. Conscious detection was not uniformly distributed across the cardiac cycle but significantly higher in diastole than in systole. We found no evidence that the heart rate before a stimulus influenced its detection, but hits (correctly detected somatosensory stimuli) led to a more pronounced cardiac deceleration than misses. Our findings demonstrate interactions between cardiac activity and conscious somatosensory perception, which highlights the importance of internal bodily states for sensory processing beyond the auditory and visual domain

Olfaction-enhanced multimedia: Perspectives and challenges

This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2011 Springer VerlagOlfaction—or smell—is one of the last challenges which multimedia and multimodal applications have to conquer. Enhancing such applications with olfactory stimuli has the potential to create a more complex—and richer—user multimedia experience, by heightening the sense of reality and diversifying user interaction modalities. Nonetheless, olfaction-enhanced multimedia still remains a challenging research area. More recently, however, there have been initial signs of olfactory-enhanced applications in multimedia, with olfaction being used towards a variety of goals, including notification alerts, enhancing the sense of reality in immersive applications, and branding, to name but a few. However, as the goal of a multimedia application is to inform and/or entertain users, achieving quality olfaction-enhanced multimedia applications from the users’ perspective is vital to the success and continuity of these applications. Accordingly, in this paper we have focused on investigating the user perceived experience of olfaction-enhanced multimedia applications, with the aim of discovering the quality evaluation factors that are important from a user’s perspective of these applications, and consequently ensure the continued advancement and success of olfaction-enhanced multimedia applications

Gender and Age Related Effects While Watching TV Advertisements: An EEG Study

The aim of the present paper is to show how the variation of the EEG frontal cortical asymmetry is related to the general appreciation perceived during the observation of TV advertisements, in particular considering the influence of the gender and age on it. In particular, we investigated the influence of the gender on the perception of a car advertisement (Experiment 1) and the influence of the factor age on a chewing gum commercial (Experiment 2). Experiment 1 results showed statistically significant higher approach values for the men group throughout the commercial. Results from Experiment 2 showed significant lower values by older adults for the spot, containing scenes not very enjoyed by them. In both studies, there was no statistical significant difference in the scene relative to the product offering between the experimental populations, suggesting the absence in our study of a bias towards the specific product in the evaluated populations. These evidences state the importance of the creativity in advertising, in order to attract the target population

Agreeable Smellers and Sensitive Neurotics – Correlations among Personality Traits and Sensory Thresholds

Correlations between personality traits and a wide range of sensory thresholds were examined. Participants (N = 124) completed a personality inventory (NEO-FFI) and underwent assessment of olfactory, trigeminal, tactile and gustatory detection thresholds, as well as examination of trigeminal and tactile pain thresholds. Significantly enhanced odor sensitivity in socially agreeable people, significantly enhanced trigeminal sensitivity in neurotic subjects, and a tendency for enhanced pain tolerance in highly conscientious participants was revealed. It is postulated that varied sensory processing may influence an individual's perception of the environment; particularly their perception of socially relevant or potentially dangerous stimuli and thus, varied with personality

Conditioned sounds enhance visual processing

This psychophysics study investigated whether prior auditory conditioning influences how a sound interacts with visual perception. In the conditioning phase, subjects were presented with three pure tones ( =  conditioned stimuli, CS) that were paired with positive, negative or neutral unconditioned stimuli. As unconditioned reinforcers we employed pictures (highly pleasant, unpleasant and neutral) or monetary outcomes (+50 euro cents, −50 cents, 0 cents). In the subsequent visual selective attention paradigm, subjects were presented with near-threshold Gabors displayed in their left or right hemifield. Critically, the Gabors were presented in synchrony with one of the conditioned sounds. Subjects discriminated whether the Gabors were presented in their left or right hemifields. Participants determined the location more accurately when the Gabors were presented in synchrony with positive relative to neutral sounds irrespective of reinforcer type. Thus, previously rewarded relative to neutral sounds increased the bottom-up salience of the visual Gabors. Our results are the first demonstration that prior auditory conditioning is a potent mechanism to modulate the effect of sounds on visual perception

Emotional enhancement of error detection : the role of perceptual processing and inhibition monitoring in failed auditory stop trials

The first aim of the present study was to test whether arousing, aversive sounds can influence inhibitory task performance and lead to increased error monitoring relative to a neutral task condition. The second aim was to examine whether the enhancement of error monitoring in an affective context (if present) could be predicted from stop-signal-related brain activity. Participants performed an emotional stop-signal task that required response inhibition to aversive and neutral auditory stimuli. The behavioral data revealed that unpleasant sounds facilitated inhibitory processing by decreasing the stop-signal reaction time and increasing the inhibitory rate relative to neutral tones. Aversive sounds evoked larger N1, P3, and Pe components, indicating improvements in perceptual processing, inhibition, and conscious error monitoring. A first regression analysis, conducted regardless of the category of the stop signal, revealed that both selected indexes of stop-signal-related brain activity - the N1 and P3 amplitudes recorded in the unsuccessfully inhibited trials - significantly accounted for the Pe component variance, explaining a large amount of the observed variation (66%). A second regression model, focused on difference measures (emotional minus neutral), revealed that the affective increase in the P3 amplitude on failed stop trials was the only factor that significantly accounted for the emotional enhancement effect in the Pe amplitude. This suggests that, in general (regardless of stop - signal condition), error processing is stronger if the erroneous response directly follows the stimulus, which was effectively processed on both the perceptual and action - monitoring levels. However, only inhibition - monitoring evidence accounts for the emotional increase in conscious error detection