Olfaction Modulates Inter-Subject Correlation of Neural Responses

Naturalistic approach to investigate the neural correlates of a laundry cycle with and without fragrance

Advancements in brain imaging technologies have facilitated the development of "real-world" experimental scenarios. In this study, participants engaged in a household chore - completing a laundry cycle - while their frontal lobe brain activity was monitored using fNIRS. Participants completed this twice using both fragranced and unfragranced detergent, to explore if fNIRS is able to identify any differences in brain activity in response to subtle changes in stimuli. Analysis was conducted using Automatic IDentification of functional Events (AIDE) software and fNIRS correlation-based signal improvement (CBSI). Results indicated that brain activity, particularly in the right frontopolar and occasionally the left dorsolateral prefrontal cortex, was more pronounced and frequent with the unfragranced detergent than the fragranced. This suggests that completing tasks in an environment where a pleasant and relaxing fragrance is present might be less effortful compared to an odourless environment.

Consistent movement of viewers' facial keypoints while watching emotionally evocative videos

Neuropsychological research aims to unravel how diverse individuals' brains exhibit similar functionality when exposed to the same stimuli. The evocation of consistent responses when different subjects watch the same emotionally evocative stimulus has been observed through modalities like fMRI, EEG, physiological signals and facial expressions. We refer to the quantification of these shared consistent signals across subjects at each time instant across the temporal dimension as Consistent Response Measurement (CRM). CRM is widely explored through fMRI, occasionally with EEG, physiological signals and facial expressions using metrics like Inter-Subject Correlation (ISC). However, fMRI tools are expensive and constrained, while EEG and physiological signals are prone to facial artifacts and environmental conditions (such as temperature, humidity, and health condition of subjects). In this research, facial expression videos are used as a cost-effective and flexible alternative for CRM, minimally affected by external conditions. By employing computer vision-based automated facial keypoint tracking, a new metric similar to ISC, called the Average t-statistic, is introduced. Unlike existing facial expression-based methodologies that measure CRM of secondary indicators like inferred emotions, keypoint, and ICA-based features, the Average t-statistic is closely associated with the direct measurement of consistent facial muscle movement using the Facial Action Coding System (FACS). This is evidenced in DISFA dataset where the time-series of Average t-statistic has a high correlation (R2 = 0.78) with a metric called AU consistency, which directly measures facial muscle movement through FACS coding of video frames. The simplicity of recording facial expressions with the automated Average t-statistic expands the applications of CRM such as measuring engagement in online learning, customer interactions, etc., and diagnosing outliers in healthcare conditions like stroke, autism, depression, etc. To promote further research, we have made the code repository publicly available.

Kokedama and essential oils had a relaxing psychophysiological effect on Taiwanese women during the COVID-19 pandemic

BACKGROUND

During the COVID-19 pandemic, we designed an indoor nature activity program for citizens with a relaxing effect similar to forest bathing to promote their physical and mental health. We integrated an indoor horticultural activity (Kokedama) with the breathing of Pseudotsuga menziesii (P. menziesii) and Lavandula angustifolia (L. angustifolia) essential oils (EOs) with the goal of creating a nature-inspired environment in an indoor setting where participants would feel as if immersed in a forest atmosphere.

METHODS

Taiwanese women participated in the experiment, using two Saturday mornings, one Saturday in a university classroom in the city center; and the other Saturday in a workshop in a Suburban Park. Intra-group comparisons were used to assess the Physiological responses to urban and suburban environmental stimuli and measured self-reported psychological responses. We recorded parameters associated with heart-rate variability and brainwaves. We also administered the State-Trait Anxiety Inventory-State (STAI-S) questionnaire before and after the participants had completed the entire program.

RESULTS

After the participants had breathed the P. menziesii and L. angustifolia EOs, the levels of some physiological parameters increased (standard deviation of normal-to-normal intervals, normalized high frequency, and high alpha wave) and those of others decreased (normalized low frequency, low- to high-frequency ratio power, high beta wave, and gamma wave). These findings were corroborated by the data from the STAI-S questionnaires.

CONCLUSIONS

The psychophysiological data from this study provide significant scientific evidence for the health benefits of an indoor nature activity program in women.

Relaxing Effects of Breathing Pseudotsuga menziesii and Lavandula angustifolia Essential Oils on Psychophysiological Status in Older Adults

We evaluated the effects of breathing Pseudotsuga menziesii (P. menziesii) and Lavandula angustifolia (L. angustifolia) essential oils (EOs) during a horticultural activity on older adults. A total number of 92 older adult (71.2 ± 7.7 years old) participants were guided through a leaf printing procedure. In the meantime, water vapor and EOs were diffused in an orderly manner. The heart rate variability-related parameters as well as the brain waves were recorded. In addition, we also collected data for the State-Trait Anxiety Inventory-State (STAI-S) questionnaires before and after the whole indoor natural activity program. The physiological parameters including standard deviation of normal to normal intervals, normalized high frequency (nHF), and high alpha wave increased while the normalized low frequency (nLF), the ratio of LF-to-HF power, high beta wave, and gamma wave decreased following the breathing of P. menziesii and L. angustifolia EOs. These changes indicated a relaxing effect of breathing both EOs during a horticultural activity on older adults. Our results demonstrated a beneficial effect of P. menziesii EO which is as good as a well-known relaxant L. angustifolia EO. This notion was supported by the results of STAI-S. Here we developed an indoor natural activity program for older adults to promote physical and mental health.

Olfactory Virtual Reality: A New Frontier in the Treatment and Prevention of Posttraumatic Stress Disorder

This perspective piece reviews the clinical condition of posttraumatic stress disorder (PTSD), which is currently increasing due to the COVID-19 pandemic, and recent research illustrating how olfaction is being incorporated into virtual reality (VR) platforms. I then discuss the latest work examining the potential of olfactory virtual reality (OVR) for the treatment of PTSD. From this foundation I suggest novel ways in which OVR may be implemented in PTSD therapy and harnessed for preventing the development of PTSD. Perceptual and chemical features of olfaction that should be considered in OVR applications are also discussed.