The impact of chemosensory dysfunctions on weight loss

Background: The role of chemosensory senses (olfaction, taste, and trigeminal) is crucial, and their dysfunctions profoundly affect the quality of life, potentially impacting eating behaviors. However, it is unclear which chemosensory symptoms could lead to undernutrition. This study aims to investigate which findings in patients' smell and taste workup are predictors of weight loss. Methods: This is a retrospective study based on a validated questionnaire consecutively given to adult patients presented in smell and taste consultations during a 10-year period. Psychophysical tests were used to measure chemosensory function (Sniffin' Sticks, taste powder, and Taste Strips tests). Results: We included 555 patients (307 females) with a median age of 51 years (IQR 23). Among them, 76 (13.7%) reported involuntary weight loss due to chemosensory disorders occurred over periods ranging from 3 to 36 months. We found that the odds of losing weight were 2.1 times higher when patients reported changes in aroma perception (p-value=0.012; 95% CI 1.15 - 3.83). Parosmia, but not phantosmia nor smell loss, was a significant predictor of weight loss (OR 2.22; p-value=0.015; 95% CI 1.17 - 4.2). Furthermore, the duration of symptoms for more than two years was protective for weight loss (OR 0.44; p-value=0.014; 95% CI 0.23 - 0.85). Regarding putative etiologies, post-traumatic chemosensory dysfunction was also a significant predictor (OR 2.08; p-value=0.039; 95% CI 1.04 - 4.16). Concerning psychophysical tests, we found that the probability of a patient to present weight loss increased by 8% for every 1-unit reduction in Taste Strips score (p-value=0.006; 95% CI 0.87 - 0.98). Conclusion: We recommend investigating weight loss in smell and taste consultations, especially when patients report changes in aroma perception, parosmia, duration of symptoms for less than two years, head injury, and when low Taste Strips score is measured.

Scaffolding depth cues and perceptual learning in VR to train stereovision: a proof of concept pilot study

Stereopsis is a valuable feature of human visual perception, which may be impaired or absent in amblyopia and/or strabismus but can be improved through perceptual learning (PL) and videogames. The development of consumer virtual reality (VR) may provide a useful tool for improving stereovision. We report a proof of concept study, especially useful for strabismic patients and/or those with reduced or null stereoacuity. Our novel VR PL strategy is based on a principled approach which included aligning and balancing the perceptual input to the two eyes, dichoptic tasks, exposure to large disparities, scaffolding depth cues and perception for action. We recruited ten adults with normal vision and ten with binocular impairments. Participants played two novel PL games (DartBoard and Halloween) using a VR-HMD. Each game consisted of three depth cue scaffolding conditions, starting with non-binocular and binocular cues to depth and ending with only binocular disparity. All stereo-anomalous participants improved in the game and most (9/10) showed transfer to clinical and psychophysical stereoacuity tests (mean stereoacuity changed from 569 to 296 arc seconds, P < 0.0001). Stereo-normal participants also showed in-game improvement, which transferred to psychophysical tests (mean stereoacuity changed from 23 to a ceiling value of 20 arc seconds, P = 0.001). We conclude that a VR PL approach based on depth cue scaffolding may provide a useful method for improving stereoacuity, and the in-game performance metrics may provide useful insights into principles for effective treatment of stereo anomalies.This study was registered as a clinical trial on 04/05/2010 with the identifier NCT01115283 at ClinicalTrials.gov.

Ophthalmic examination in the debut and during progression of neurodegenerative diseases

Neurodegenerative diseases (NDD) are a group of nosological forms, caused by excessive formation of protein molecules and their aggregates and leading to the death of brain cells. Classical pathophysiological mechanisms are associated with the accumulation of extracellular amyloid b -protein (A b) in Alzheimer's disease (AD) and a -synuclein protein in Parkinson's disease (PD), which are markers of neurodegenerative process. Signs of functional disorders in NDD include decreasing visual acuity, lower contrast light sensitivity with the most significant changes at the highest spatial frequencies (18 and 12 cycles per degree), and reduced color vision. These disorders correlate with the severity of cognitive impairment and duration of the disease. Changes in the indicators of psychophysical tests are accompanied by lower central retinal thickness (CRT), which is a consequence of inner layers degeneration. NDD progression is characterized by the stability of psychophysical tests, significant thinning of the peripapillary retinal nerve fiber layer (RNFL) and CRT thickening, which correlates with cognitive disfunction. A b and a -synuclein deposits in artery walls cause lumen narrowing and occlusion of blood vessels, reduced optic nerve disk perfusion density, superficial and deep capillary plexus depletion, expansion of the avascular foveolar zone. Microcirculatory disorders lead to retinal changes, which were proven to correlate negatively with the thickness of inner retinal layers and duration of the disease. An ever-growing need in the identification of specific and sensitive biomarkers at the preclinical stage of NDDs, differentiation of their causes, precise subtype classification, and assessment of progression risk is an evidence of the relevance of studying and identifying functional and structural changes in retinal neurons and axons. Non-invasive and informative methods of multimodal imaging appear to be valuable for NDD diagnosis and monitoring.

­Scaffolding Depth Cues and Perceptual Learning in VR to Train Stereovision: A Proof of Concept Pilot Study

Stereopsis is a valuable feature of human visual perception, which may be impaired or absent in amblyopia and/or strabismus but can be improved through perceptual learning (PL) and videogames. The development of consumer virtual reality (VR) may provide a useful tool for improving stereovision. We report a proof of concept study, especially useful for strabismic patients and/or those with reduced or null stereoacuity. Our novel VR PL strategy is based on a principled approach which included aligning and balancing the perceptual input to the two eyes, dichoptic tasks, exposure to large disparities, scaffolding depth cues and perception for action. We recruited ten adults with normal vision and ten with binocular impairments. Participants played two novel PL games (DartBoard and Halloween) using a VR-HMD. Each game consisted of three depth cue scaffolding conditions, starting with non-binocular and binocular cues to depth and ending with only binocular disparity. All stereo-anomalous participants improved in the game and most (9/10) showed transfer to clinical and psychophysical stereoacuity tests (mean stereoacuity changed from 569 to 296 arc seconds, p<0.0001). Stereo-normal participants also showed in-game improvement, which transferred to psychophysical tests (mean stereoacuity changed from 23 to a ceiling value of 20 arc seconds, p=0.001). We conclude that a VR PL approach based on depth cue scaffolding may provide a useful method for improving stereoacuity, and the in-game performance metrics may provide useful insights into principles for effective treatment of stereo anomalies.

Comparison of COVID-19 and common cold chemosensory dysfunction

Anosmia constitutes a prominent symptom of COVID-19. However, anosmia is also a common symptom of acute colds of various origins. In contrast to an acute cold, it appears from several questionnaire-based studies that in the context of COVID-19 infection, anosmia is the main rhinological symptom and is usually not associated with other rhinological symptoms such as rhinorrhoea or nasal obstruction. Until now, no study has directly compared smell and taste function between COVID-19 patients and patients with other causes of upper respiratory tract infection (URTI) using valid and reliable psychophysical tests. In this study, we aimed to objectively assess and compare olfactory and gustatory functions in 10 COVID-19 patients (PCR diagnosed, assessed on average 2 weeks after infection), 10 acute cold (AC) patients (assessed before the COVID-19 outbreak) and 10 healthy controls, matched for age and sex. Smell performance was assessed using the extended "Sniffin' Sticks" test battery (4), while taste function was assessed using "taste strips" (5). Receiver Operating Characteristic (ROC) curves were built to probe olfactory and gustatory scores in terms of their discrimination between COVID-19 and AC patients. Our results suggest that mechanisms of COVID-19 related olfactory dysfunction are different from those seen in an AC and may reflect, at least to some extent, a specific involvement at the level of central nervous system in some COVID-19 patients. In the future, studies to assess the prevalence of persistent anosmia and neuroanatomical changes on MRI correlated to chemosensory function, will be useful to understand these mechanisms.

Tactile display of softness on fingertip

Multi-sensory human–machine interfaces are currently challenged by the lack of effective, comfortable and affordable actuation technologies for wearable tactile displays of softness in virtual- or augmented-reality environments. They should provide fingertips with tactile feedback mimicking the tactual feeling perceived while touching soft objects, for applications like virtual reality-based training, tele-rehabilitation, tele-manipulation, tele-presence, etc. Displaying a virtual softness on a fingertip requires the application of quasi-static (non-vibratory) forces via a deformable surface, to control both the contact area and the indentation depth of the skin. The state of the art does not offer wearable devices that can combine simple structure, low weight, low size and electrically safe operation. As a result, wearable softness displays are still missing for real-life uses. Here, we present a technology based on fingertip-mounted small deformable chambers, which weight about 3 g and are pneumatically driven by a compact and cost-effective unit. Weighting less than 400 g, the driving unit is easily portable and can be digitally controlled to stimulate up to three fingertips independently. Psychophysical tests proved ability to generate useful perceptions, with a Just Noticeable Difference characterised by a Weber constant of 0.15. The system was made of off-the-shelf materials and components, without any special manufacturing process, and is fully disclosed, providing schematics and lists of components. This was aimed at making it easily and freely usable, so as to turn tactile displays of softness on fingertips into a technology ‘at fingertips’.

StimuliApp: Psychophysical tests on mobile devices

Psychophysical tests are commonly carried out using software applications running on desktop or laptop computers, but running the software on mobile handheld devices such as smartphones or tablets could have advantages in some situations. Here, we present StimuliApp, an open-source application in which the user can create psychophysical tests on the iPad and the iPhone by means of a system of menus. A wide number of templates for creating stimuli are available including patches, gradients, gratings, checkerboards, random-dots, texts, tones or auditory noise. Images, videos and audios stored in files could also be presented. The application was developed natively for iPadOS and iOS using the low-level interface Metal for accessing the graphics processing unit, which results in high timing performance.

Motion sensitivity assessment based on an analysis of the spatio-temporal features of eye movements

Motion sensitivity refers to the individual’s ability to detect and perceive motion in the environment. It is a fundamental property of visual perception, crucial for orientation and navigation in the environment. Yet, its behavioral assessment is usually tedious and time-consuming, limiting assessment in clinical and rehabilitation contexts. Assessment of eye-movements may provide a more observer-friendly way to obtain the same information. For this reason, in this study, we evaluated the suitability of an eye-movement-based method to assess various aspects of motion sensitivity. To do so, we quantify the spatio-temporal features of eye-movements made during a smooth pursuit task at different velocities. We found that the temporal and spatial uncertainties robustly reflected the changes in stimulus speed. Furthermore, we measured motion sensitivity using a conventional random dot kinematogram-based direction discrimination task. We found that none of the spatio-temporal features computed from the tracking task were correlated with the psychophysical motion sensitivity measures (slope and threshold) obtained with the random dot kinematogram. We conclude that continuous visual tracking efficiently assesses specific aspects of motion processing in an observer-friendly manner. Moreover, the approach provides information that is complementary to that obtained through conventional psychophysical tests such as the random dot kinematogram.

Objective Olfactory Findings in Hospitalized Severe COVID-19 Patients

Objective: We investigate the prevalence of the self-reported and objective sudden loss of smell (SLS) in patients with severe coronavirus disease 2019 (COVID-19). Methods: Severe COVID-19 patients with self-reported SLS were recruited at hospitalization discharge. Epidemiological and clinical data were collected. The Sino-nasal Outcome Test-22 (SNOT-22) was used to evaluate rhinological complaints. Subjective olfactory and gustatory functions were assessed with the National Health and Nutrition Examination Survey (NHNES). Objective SLS was evaluated using psychophysical tests. Potential associations between olfactory evaluation and the clinical outcomes (duration of hospitalization; admission biology; one month serology (IgG), and chest computed tomography findings) were studied. Results: Forty-seven patients completed the study (25 females). Subjectively, eighteen (38.3%) individuals self-reported subjective partial or total SLS. Among them, only three and four were anosmic and hyposmic, respectively (38.9%). Considering the objective evaluation in the entire cohort, the prevalence of SLS was 21.3%. Elderly patients and those with diabetes had lower objective olfactory evaluation results than young and non-diabetic individuals. Conclusions: The prevalence of SLS in severe COVID-19 patients appears to be lower than previously estimated in mild-to-moderate COVID-19 forms. Future comparative studies are needed to explore the predictive value of SLS for COVID-19 severity.