Improved low-cost, MR-compatible olfactometer to deliver tobacco smoke odor

Development and Study of Ezzence: A Modular Scent Wearable to Improve Wellbeing in Home Sleep Environments

Ezzence is the first smartphone-controlled olfactometer designed for both day and night conditions. We discuss the design and technical implementation of Ezzence and report on a study to evaluate the feasibility of using the device in home-based sleep environments. The study results (N = 40) show that participants were satisfied with the device and found it easy to use. Furthermore, participants reported a significant improvement in sleep quality when using the device with scent in comparison to the control condition (p = 0.003), as well as better mood the following morning (p = 0.038) and shorter time to sleep onset (p = 0.008). The device is integrated with a wearable EEG and real-time sleep staging algorithm to release scent during specific sleep stages (N1, N2, N3, and REM), which is important for certain use cases (e.g., to study the effect of scent on REM dreams, or to improve memory consolidation with a re-exposure of scent during N2 and N3). Ezzence can be used for several applications, including those that require scent triggered day and night. They include targeted memory reactivation, longitudinal health treatments, therapy, and mental or physical exercises. Finally, this article proposes an interaction framework to understand relationships between scents and environments based on proxemic dimensions and passive or active interactions during sleep.

Odor Canopy: A Method for Comfortable Odorant Delivery in MRI

Functional magnetic resonance imaging (fMRI) has become the leading method for measuring the human brain response to sensory stimuli. However, olfaction fMRI lags behind vision and audition fMRI for 2 primary reasons: First, the olfactory brain areas are particularly susceptible to imaging artifacts, and second, the olfactory stimulus is particularly difficult to control in the fMRI environment. A component of the latter is related to the odorant delivery human–machine interface, namely the point where odorants exit the dispensing apparatus to reach at the nose. Previous approaches relied on either nasal cannulas or nasal masks, each associated with particular drawbacks and discomforts. Here, we provide detailed descriptions and instructions for transforming the MRI head-coil into an olfactory microenvironment, or odor canopy, where odorants can be switched on and off in less than 150 ms without cannula or mask. In a proof-of-concept experiment, we demonstrate that odor canopy provides for clearly dissociable odorant presence and absence, with no nonolfactory cues. Moreover, we find that odor canopy is rated more comfortable than nasal mask, and we demonstrate that using odor canopy in the fMRI generates a typical olfactory brain response. We conclude in recommending this approach for minimized discomfort in fMRI of olfaction.

A multimodal MR-compatible olfactometer with real-time controlling capability

Design of an MR-compatible and computer-controlled odour stimuli system is essential in the studies of human olfactory function. Olfactometers are used to deliver odours to the subjects in an objective manner. We present a portable, computer-controlled eight channels olfactometer able to stimulate olfaction by employing liquid odorant stimuli. We used a high-pressure pump to generate medical grade airflow. After passing through solenoid valve-controlled odour reservoirs, odorant stimulus is conveyed to the nasal mask. The odour delivery delay of the device was measured using photo-ionisation detectors. To assess the application of the designed olfactometer, an fMRI experiment was done with 9 healthy subjects. Two odour stimuli (Vanillin and Rose) were presented to each subject in an alternating block design task of odour and non-odour conditions. The response time of each subject was gathered using the response box. Group analysis revealed a significant BOLD signal change in some regions of olfactory and trigeminal networks including the orbitofrontal cortex, insula, inferior frontal gyrus, hippocampus, cingulate gyrus and piriform cortex. The odour delivery delay measured by photo-ionisation detector was 190 ms, and the subjects' response showed 205 ms for the Vanillin and 243 ms for the Rose odour stimuli. Our portable MR-compatible olfactometer as a stimulation device is capable of creating adequate stimulation suitable for olfactory fMRI experiments.

Continuous Theta Burst Stimulation Over the Right Orbitofrontal Cortex Impairs Conscious Olfactory Perception

The right orbitofrontal cortex (rOFC) has been proposed as the region where conscious olfactory perception arises; however, evidence supporting this hypothesis has all been collected from neuroimaging and lesion studies in which only correlation and not a temporal pattern can be established. Continuous theta burst stimulation (cTBS) causes a reversible disruption of cortical activity and has been used successfully to disrupt orbitofrontal activity. To overcome intrinsic limitations of current experimental research, a crossover, double-blind, prospective and longitudinal study was carried out in which cTBS was applied over the rOFC to evaluate its effect on odorant stimuli detection. All subjects received real and sham cTBS. Experimental procedures were done in two different sessions with a separation of at least one week between them to avoid carryover and learning effects. A total of 15 subjects completed the experiment, and their data were included in the final analysis (10 women, 5 men, mean age 22.40 ± 3.41). Every session consisted of two different measures of the conscious olfactory perception task: A baseline measure and one 5 min after cTBS/sham. Compared to baseline, marks in the olfactory task during the sham cTBS session increased (p = 0.010), while marks during the real cTBS session decreased (p = 0.017). Our results support the hypothesis that rOFC is an important node of a complex network required for conscious olfactory perception to arise. However, the exact mechanism that explains our results is unclear and could be explained by the disruption of other cognitive functions related to the rOFC.

Multisensory Environments to Measure Craving During Functional Magnetic Resonance Imaging

There are limited functional magnetic resonance imaging (fMRI) studies that measure alcohol craving with multisensory environments. Researchers are faced with a two-fold challenge: to recreate a naturalistic environment during an MRI scan and to produce paradigms that mimic real-life conditions involved with craving. Craving is a multifaceted psychological construct and techniques such as fMRI provide an alternative way to measure craving and to have a better understanding of its complexity. Most studies to date have implemented visual stimuli to measure craving and only a few studies have investigated gustation and olfaction. Moving forward, there needs to be greater attention on the ways in which we measure craving and the use of multisensory environments during fMRI. By going beyond examining subjective craving responses, and investigating neurobiological responses such as brain activity during fMRI, can potentially lead to better treatments for alcohol use disorder. Further, there needs to be additional consideration on standardizing how we measure craving, which will allow for a more unified approach amongst researchers.

Investigating the neural correlates of smoking: Feasibility and results of combining electronic cigarettes with fMRI

Cigarette addiction is driven partly by the physiological effects of nicotine, but also by the distinctive sensory and behavioural aspects of smoking, and understanding the neural effects of such processes is vital. There are many practical difficulties associated with subjects smoking in the modern neuroscientific laboratory environment, however electronic cigarettes obviate many of these issues, and provide a close simulation of smoking tobacco cigarettes. We have examined the neural effects of 'smoking' electronic cigarettes with concurrent functional Magnetic Resonance Imaging (fMRI). The results demonstrate the feasibility of using these devices in the MRI environment, and show brain activation in a network of cortical (motor cortex, insula, cingulate, amygdala) and sub-cortical (putamen, thalamus, globus pallidus, cerebellum) regions. Concomitant relative deactivations were seen in the ventral striatum and orbitofrontal cortex. These results reveal the brain processes involved in (simulated) smoking for the first time, and validate a novel approach to the study of smoking, and addiction more generally.