Robert Pellegrino

Chemical complexity of odors increases reliability of olfactory threshold testing

Assessment of odor thresholds is a widely recognized method of measuring olfactory abilities in humans. To date no attempts have been made to assess whether chemical complexity of odors used can produce more reliable results. To this end, we performed two studies of repeated measures design with 121 healthy volunteers (age 19–62 years). In Study 1, we compared thresholds obtained from tests based on one odor presented in a pen-like odor dispensing device with three odors and six odors mixtures presented in glass containers. In study 2 we compared stimuli of one and three odors, both presented in glass containers. In both studies measurements were performed twice, separated by at least three days. Results indicate that the multiple odor mixtures produced more reliable threshold scores, as compared to thresholds based on a single substance.

Olfactory function in patients with hyposmia compared to healthy subjects - An fMRI study.

BACKGROUND Individuals with hyposmia, or the partial loss of smell, represent a large sector (15 %) of the population that is likely to grow with the current aging population; however, our understanding to how hyposmics centrally process odors is still not clear. One popular non-invasive tool for in vivo imaging of biological activity among human brains has been function magnetic resonance imaging (fMRI) which uses blood-oxygenation level dependent (BOLD) signal as an indirect measurement. Therefore, the aim of this study was to understand differences in olfaction processing between patients with hyposmia and healthy controls using functional magnetic resonance imaging (fMRI). METHODOLOGY Eleven hyposmic and 12 healthy, normosmic subjects were exposed to two different food-related odors (coffee and peach) during a block-designed fMRI session. Additionally, odor perception qualities were rated for each odor throughout the scanning session. RESULTS The activations of the normosmic group were localized in typical olfactory areas (insula, orbitofrontal cortex [OFC], limbic system and amygdala). The hyposmic group showed similar regions of activation (insula, OFC, limbic system), however, less activation was found in the amygdala, left anterior cingulate and right OFC, but higher activation was shown in the right parahippocampal and both the left and right posterior cingulate gyrus which are assumed to play an important role in the processing and remembrance of memories. CONCLUSIONS These results indicate similar central olfactory processing among groups, yet subjects with partial loss may attempt to compensate smell impairment with odor memory or higher motivation to smell.

Using Olfaction and Unpleasant Reminders to Reduce the Intention-behavior Gap in Hand Washing

Lack of hand washing is a leading cause of food borne illnesses. To successfully increase hand hygiene compliance, interventions must have continual engagement with employees. This study used a real-time prospective memory (PM) scenario to measure the effectiveness of a control and sensory reminders of disgust to influence hand washing behavior and performance. First, a model of hand washing performance was built by having six participants’ hands contaminated with GermGlo (a florescent micro-particle) and then washed their hands using predetermined protocols while monitored by an electronic hand hygiene verification (HHV) system. Next, eighty Hispanic/Latino participants, in a between-group experimental design, performed a PM experiment while one of four reminders were present (hand washing poster, disgusting image, disgusting sound, and disgusting odor) as the HHV recorded their hand washing performance. Visual cues, typical of hand washing campaigns, were not as effective at increasing hand hygiene compliance as disgust-induced sensory cues. Furthermore, olfactory disgust showed a significantly higher probability that individuals would engage in hand washing behaviors than all other conditions. This study provides new insight into the effectiveness of different senses and emotion to reduce the intention-behavior gap associated with modifying behaviors, and broadens current PM research to a real-time application.

Habituation and adaptation to odors in humans

Habituation, or decreased behavioral response, to odors is created by repeated exposure and several detailed characteristics, whereas adaptation relates to the neural processes that constitute this decrease in a behavioral response. As with all senses, the olfactory system continually encounters an enormous variety of odorants which is why mechanisms must exist to segment them and respond to changes. Although most olfactory habitation studies have focused on animal models, this non-systematic review provides an overview of olfactory habituation and adaptation in humans, and techniques that have been used to measure them. Thus far, psychophysics in combination with modern techniques of neural measurement indicate that habituation to odors, or decrease of intensity, is relatively fast with adaptation occurring more quickly at higher cerebral processes than peripheral adaptation. Similarly, it has been demonstrated that many of the characteristics of habitation apply to human olfaction; yet, evidence for some characteristics such as potentiation of habituation or habituation of dishabituation need more support. Additionally, standard experimental designs should be used to minimize variance across studies, and more research is needed to define peripheral-cerebral feedback loops involved in decreased responsiveness to environmental stimuli.

Time frequency analysis of olfactory induced EEG-power change

Objectives The objective of the present study was to investigate the usefulness of time-frequency analysis (TFA) of olfactory-induced EEG change with a low-cost, portable olfactometer in the clinical investigation of smell function. Materials & methods A total of 78 volunteers participated. The study was composed of three parts where olfactory stimuli were presented using a custom-built olfactometer. Part I was designed to optimize the stimulus as well as the recording conditions. In part II EEG-power changes after olfactory/trigeminal stimulation were compared between healthy participants and patients with olfactory impairment. In Part III the test-retest reliability of the method was evaluated in healthy subjects. Results Part I indicated that the most effective paradigm for stimulus presentation was cued stimulus, with an interstimulus interval of 18-20s at a stimulus duration of 1000ms with each stimulus quality presented 60 times in blocks of 20 stimuli each. In Part II we found that central processing of olfactory stimuli analyzed by TFA differed significantly between healthy controls and patients even when controlling for age. It was possible to reliably distinguish patients with olfactory impairment from healthy individuals at a high degree of accuracy (healthy controls vs anosmic patients: sensitivity 75%; specificity 89%). In addition we could show a good test-retest reliability of TFA of chemosensory induced EEG-power changes in Part III. Conclusions Central processing of olfactory stimuli analyzed by TFA reliably distinguishes patients with olfactory impairment from healthy individuals at a high degree of accuracy. Importantly this can be achieved with a simple olfactometer.

Investigation of chemosensitivity during and after an acute cold

Viral rhinitis (the “common” cold) is a frequent worldwide disease. Olfactory dysfunction is one complication that arises during infection, which in most cases heals up spontaneously upon recovery, whereas in some cases it may persist as a partial or total loss of olfaction. The aim of this prospective study was to investigate the change of other chemosensory systems during a cold.

Temporal Encoding During Unimodal and Bimodal Odor Processing in the Human Brain

IntroductionIn daily life, people encounter a wide range of odors, most of which contain multiple chemical substances. So-called bimodal odors stimulate both the olfactory and trigeminal nerve, and the interaction between these two systems shapes the perception of the odor. However, temporal encoding of these sensory systems during bimodal odor processing has received limited scientific attention.MethodsTo investigate this, we recorded the electrophysiological response in 17 participants to relatively unimodal olfactory (strawberry), trigeminal (l-isopulegol) and strongly bimodal (strawberry and l-isopulegol) stimuli.ResultsERP amplitudes and intensity ratings were significantly bigger for bimodal stimulation, as compared to unimodal stimulations. No significant difference was observed between N1 and P2 response latencies to olfactory and bimodal stimuli while responses to both stimuli showed longer latencies compared to the response of the trigeminal stimulus.ConclusionsResults provide further evidence of interaction between olfactory and trigeminal systems; additional activation of the olfactory system results in more vigorous electrophysiological responses and the experience of higher intensity. In addition, results indicate that the trigeminal system is faster to react to stimulation.ImplicationsThe current study offers a view on the temporal processing of bimodal odorants that are most likely to be encountered in the environment. We link the more vigorous electrophysiological response to a more complex odorant with activation of different neural structures.

The influence of condiment availability on cuisine selection

Purpose In most restaurants or dining facilities, even though a set of condiments such as salt, black pepper, ketchup, and mustard, is placed on the tables, and such condiments are a staple of many cuisines, they have been largely ignored with respect to understanding their effects on food choice. The purpose of this study is to determine whether condiments placed on tables at dining facilities can affect consumers’ cuisine selection. Design/methodology/approach Four individual booths were set up with four different condiment configurations: 1) branded ketchup and mustard, 2) unbranded ketchup and mustard, 3) unbranded soy sauce and chili-garlic sauce, and 4) no condiment. In all, 68 participants were assigned in random sequence to all booths, with each given a menu listing nine different cuisines (three North American, three Asian, and three Hispanic cuisines) in a random order, and asked to identify their top three preferred cuisines at each booth. Findings Participants chose Asian cuisines with higher priority than Mexican and North American selections when Asian condiments were placed on the table. Interestingly, this effect occurred only when the participants had noticed the condiment setting, but not when they had unnoticed it. Such Asian condiment availability-induced cuisine selection was also more pronounced for external eaters. Research limitations/implications Food service professionals and business owners, especially in food courts comprised of a variety of ethnic food vendors, should perhaps consider placing a set of condiments associated with their target cuisines at visible table spaces at dining facilities, thereby leading customers to select their cuisine items. Originality/value This study provides new empirical evidence that consumers are more likely to select cuisines congruent to the choice of condiment setting placed on their dining table.