Vestibulo-Ocular Reflex Modification after Virtual Environment Exposure

Immersion in an illusory world is possible by means of virtual reality (VR), where environmental perception is modi bff c1c ed by artificial sensorial stimulation. The application of VR for the assessment and rehabilitation of pathologies affecting the vestibular system, in terms of both diagnosis and care, could represent an interesting new line of research. Our perception of reality is in fact based on static and dynamic spatial information perceived by our senses. During head movements in a virtual environment the images on the display and the labyrinthine information relative to the head angular accelerations differ and therefore a visuo-vestibular conflict is present. It is known that mismatches between visual and labyrinthine information may modify the vestibulo-oculomotor reflex (VOR) gain. We studied the post-immersion modifications in 20 healthy subjects (mean age 25 years) exposed to a virtual environment for 20 min by wearing a head-mounted display. VOR gain and phase were measured by means of harmonic sinusoidal stimulation in the dark before, at the end of and 30 min after VR exposure. A VOR gain reduction was observed in all subjects at the end of VR exposure which disappeared after 30 min. Our data show that exposure to a virtual environment can induce a temporary modi bff c1c cation of the VOR gain. This bff c1c nding can be employed to enable an artificial, instrumental modification of the VOR gain and therefore opens up new perspectives in the assessment and rehabilitation of vestibular diseases

Site Saturation Mutagenesis Demonstrates a Central Role for Cysteine 298 as Proton Donor to the Catalytic Site in CaHydA [FeFe]-Hydrogenase

[FeFe]-hydrogenases reversibly catalyse molecular hydrogen evolution by reduction of two protons. Proton supply to the catalytic site (H-cluster) is essential for enzymatic activity. Cysteine 298 is a highly conserved residue in all [FeFe]-hydrogenases; moreover C298 is structurally very close to the H-cluster and it is important for hydrogenase activity. Here, the function of C298 in catalysis was investigated in detail by means of site saturation mutagenesis, simultaneously studying the effect of C298 replacement with all other 19 amino acids and selecting for mutants with high retained activity. We demonstrated that efficient enzymatic turnover was maintained only when C298 was replaced by aspartic acid, despite the structural diversity between the two residues. Purified CaHydA C298D does not show any significant structural difference in terms of secondary structure and iron incorporation, demonstrating that the mutation does not affect the overall protein fold. C298D retains the hydrogen evolution activity with a decrease of kcat only by 2-fold at pH 8.0 and it caused a shift of the optimum pH from 8.0 to 7.0. Moreover, the oxygen inactivation rate was not affected demonstrating that the mutation does not influence O2 diffusion to the active site or its reactivity with the H-cluster. Our results clearly demonstrate that, in order to maintain the catalytic efficiency and the high turnover number typical of [FeFe] hydrogenases, the highly conserved C298 can be replaced only by another ionisable residue with similar steric hindrance, giving evidence of its involvement in the catalytic function of [FeFe]-hydrogenases in agreement with an essential role in proton transfer to the active site. © 2012 Morra et al

Postural control in horizontal benign paroxysmal positional vertigo

Sixteen patients affected by benign paroxysmal positional vertigo of the horizontal semicircular canal (BPPV-HSC) were investigated by means of dynamic posturography (DP) and during bithermal caloric stimulation. Data were compared to data from 40 patients with benign paroxysmal positional vertigo of the posterior semicircular canal (BPPV-PSC) and 20 healthy controls. No postural deficit was observed before or after a liberative Lempert's manoeuvre when patients were compared to control subjects. BPPV-PSC postural scores were significantly impaired compared to scores from the BPPV-HSC group. A residual significant postural impairment was also observed after a successful liberative manoeuvre in the BPPV-PSC group. Electronystagmographic recordings before recovery revealed significant hypoexcitability of the affected ear in 8/16 patients of the BPPV-HSC group. After the liberative manoeuvre, a symmetric bilateral response to caloric stimulation was recorded in all patients. Three main conclusions can be drawn from the present data. First, disorders of the horizontal semicircular canal do not change postural control. Second, dynamic posturography can detect the postural imbalance due to posterior semicircular canal dysfunction even after resolution of paroxysmal vertigo attacks. Third, utricular dysfunction can be ruled out as a cause of the residual postural deficit observed in BPPV-PSC patients. Therefore the recovery delay observed even 1 month after the liberative manoeuvre in the BPPV-PSC-group might be due to the persistence of small amounts of residual debris in the canal, to paralysis of ampullar receptors, or to the time needed for central vestibular re-adaptation

Virtual reality in vestibular assessment and rehabilitation

Previous experiences on vestibular compensation showed that multisensorial stimulations affect postural unbalance recovery. Virtual Environment (VE) exposure seems very useful in vestibular rehabilitation, since the experience gained during VE exposure is transferable to the reai world. The rearrangement of the hierarchy of the postural cues was evaluated in 105 patients affected by visual, labyrinthic and somatosensory pathology in normal conditions and during sensoriai deprivation. They were divided into five groups according to pathology and compared to 50 normal controls. Our data show that VE exposure is a reliable method to identify the deficient subsystem and the level of substitution. Moreover, Virtual Reality (VR) would accelerate the compensation of an acute loss of labyrinthine function, related to adaptive modifications of thevestibulo-ocularandvestibulo-spinal reflexes, overstimulating the residual labyrinthine function. The residual labyrinthine function is poor in chronic bilateral vestibular deficit and VE exposure should provide sensory substitution or sensory motor reorganisation, thereby modulating the external spatial reference and promoting the reorganisation of the multiple sensory input. The potential for VE exposure perspectives seerns very promising when dealing with the vestibular system where there is a continuous rearrangement of different sensorial informations as a result of environmental and age-related changes

Understanding Events by Eye and Ear: Agent and Verb Drive Non-anticipatory Eye Movements in Dynamic Scenes

As Macnamara (1978) once asked, how can we talk about what we see? We report on a study manipulating realistic dynamic scenes and sentences aiming to understand the interaction between linguistic and visual representations in real-world situations. Specifically, we monitored participants’ eye movements as they watched video clips of everyday scenes while listening to sentences describing these scenes. We manipulated two main variables. The first was the semantic class of the verb in the sentence and the second was the action/motion of the agent in the unfolding event. The sentences employed two verb classes–causatives (e.g., break) and perception/psychological (e.g., notice)–which impose different constraints on the nouns that serve as their grammatical complements. The scenes depicted events in which agents either moved toward a target object (always the referent of the verb-complement noun), away from it, or remained neutral performing a given activity (such as cooking). Scenes and sentences were synchronized such that the verb onset corresponded to the first video frame of the agent motion toward or away from the object. Results show effects of agent motion but weak verb-semantic restrictions: causatives draw more attention to potential referents of their grammatical complements than perception verbs only when the agent moves toward the target object. Crucially, we found no anticipatory verb-driven eye movements toward the target object, contrary to studies using non-naturalistic and static scenes. We propose a model in which linguistic and visual computations in real-world situations occur largely independent of each other during the early moments of perceptual input, but rapidly interact at a central, conceptual system using a common, propositional code. Implications for language use in real world contexts are discussed

Scanning electron microscopy of cochlea in new-born rats exposed to hyperbaric oxygen: preliminary report

The aetiology of hearing loss in new-borns in neonatal intensive care is still debated. While the physiopathology of brain, lung and retina damage related to oxygen supplementation has been widely described, no studies have been carried out to define the relationship between hearing loss and supplementation of oxygen in new-borns. In the present investigation, the cochlear morphology of new-born rats was evaluated by means of scanning electron microscopy in order to assess morphological changes after supplemental oxygen administration. After treatment, electron microscopy revealed many changes in the morphology of outer hair cells, if compared to normal rats of the same age. The results suggest that cochlear changes are similar to those previously observed in other regions and may be related to a vascular mechanism of hypoxia-ischaemia and neovascularization and/or an oxidative stress

Scanning electron microscopy of cochlea in new-born rats exposed to hyperbaric oxygen: preliminary report

The aetiology of hearing loss in new-borns in neonatal intensive care is still debated. While the physiopathology of brain, lung and retina damage related to oxygen supplementation has been widely described, no studies have been carried out to define the relationship between hearing loss and supplementation of oxygen in new-borns. In the present investigation, the cochlear morphology of new-born rats was evaluated by means of scanning electron microscopy in order to assess morphological changes after supplemental oxygen administration. After treatment, electron microscopy revealed many changes in the morphology of outer hair cells, if compared to normal rats of the same age. The results suggest that cochlear changes are similar to those previously observed in other regions and may be related to a vascular mechanism of hypoxia-ischaemia and neovascularization and/or an oxidative stress

Nasal lavage CCL24 levels correlate with eosinophils trafficking and symptoms in chronic sino-nasal eosinophilic inflammation

OBJECTIVES: The aim of our study was to measure CCL24 (eotaxin-2) levels in nasal lavage fluid of patients with different forms of sinonasal chronic eosinophilic inflammation to verify the relationship with nasal hypereosinophilia and symptoms. METHODS: Patients with nasal hypereosinophilia were randomly recruited and grouped in persistent allergic rhinitis, non-allergic rhinitis with eosinophilia syndrome (NARES) and chronic rhinosinusitis with polyps. Non rhinitic volunteers were recruited as controls. CCL24 concentration was measured by `Quantikine Human CCL24 Immunoassay`. Differential cell counts were performed by microscopic cytological examination of nasal tissue scraped by inferior turbinate. RESULTS: CCL24 levels measured in patient groups were significantly higher compared to control group with the highest levels in NARES patients. Eotaxin- 2 levels were significantly correlated to severity of symptoms and to the percentage of eosinophils in nasal tissue. CONCLUSIONS: We revealed high levels of CCL24 in all patient groups showing a significant correlation with the degree of eosinophilia and clinical symptoms. A prolonged accumulation of CCL24 inside the nasal mucosa may sustain the process of unspecific self-perpetuating eosinophil recruitment pathognomonic of these patients

Ruolo della sleep endoscopy nella selezione dei pazienti affetti da sindrome delle apnee ostruttive durante il sonno di grado lieve moderato candidati a terapia ortodontica con dispositivo di avanzamento mandibolare

Il trattamento con dispositivi di avanzamento mandibolare (MAD) rappresenta un’efficace alternativa terapeutica per i pazienti affetti da roncopatia semplice, OSAS di grado lieve/moderato e in casi selezionati di OSAS grave con scarsa tollerabilità alla terapia ventilatoria con C-PAP. Pertanto è importante identificare dei criteri oggettivi per selezionare i pazienti che possono beneficiare del trattamento con i sistemi di avanzamento mandibolare (MAD). In letteratura sono stati descritti vari fattori predittivi sia antropometrici che polisonnografici, mentre esistono ancora controversie circa il ruolo della Sleep Endoscopy e della manovra di avanzamento mandibolare bimanuale durante lo stesso esame come fattori predittivi del successo terapeutico con MAD. In questo studio descriviamo la nostra esperienza nel management di pazienti affetti da OSAS lieve/moderata trattati con MAD e selezionati mediante “sleep endoscopy”. Abbiamo eseguito una valutazione prospettica longitudinale di una serie consecutiva di pazienti giunti alla nostra osservazione con diagnosi di OSAS lieve/moderata e sottoposti a sleependoscopy. Durante il sonno indotto farmacologicamente è stata eseguita una delicata manovra di avanzamento mandibolare con escursione inferiore ai 5 mm e abbiamo riscontrato che in 30 dei 65 pazienti (46,2%) lo spazio respiratorio non migliorava in modo significativo a livello dei siti di ostruzione osservati, mentre in 35 dei 65 pazienti (53,8%) si osservava un miglioramento significativo tale da poter indicare terapia con MAD. In 7 dei 35 pazienti venivano riscontrate condizioni che ostacolavano l’applicazione del MAD per cui 28 dei 35 pazienti sono stati sottoposti a terapia con MAD. Dopo 3 mesi di trattamento abbiamo documentato un miglioramento significativo dell’indice di Epworth medio [(7,35 ± 2,8 vs 4,1 ± 2,2 (p < 0.05)], dell’AHI medio [(21.4 ± 6 eventi per ora verso 8,85 ± 6,9 (p < 0.05) ] e dell’ODI medio [(18.6 ± 8 eventi per ora versus 7 ± 5.8 (p < 0.05)]. Abbiamo inoltre osservato che l’AHI migliorava di almeno il 50% rispetto al basale nel 71.4% dei pazienti selezionati mediante sleep endoscopy. In questo studio, la terapia con i dispositivi di avanzamento mandibolare è stata prescritta con successo sulla base non soltanto dell’indice di apnea/ipopnea, ma anche dei reperti della sleep endoscopy e della manovra di avanzamento mandibolare, ottenendo una visione diretta degli effetti della protrusione mandibolare sullo spazio respiratorio in corrispondenza dei siti di ostruzione, e ottenendo una buona ottimizzazione della selezione dei pazienti per il trattamento con MAD