Breaks in Presence in Virtual Environments: An Analysis of Blood Flow Velocity Responses

One of the techniques used to monitor variations in presence during a virtual reality experience is the analysis of breaks in presence (BIPs). Previous studies have monitored peripheral physiological responses during BIPs in order to find a characteristic physiological response. In this work, blood flow velocity (BFV) in middle cerebral arteries (MCAs) has been monitored using transcranial Doppler ultrasound during the exposure to a virtual environment. Two BIPs of different intensity were forced during the virtual reality experience. Variations in BFV during each BIP and during the recovery periods that followed them have been analyzed. A decreasing trend was observed in BFV signal during the most intense BIP in most subjects. However, during the less intense BIP an oscillating behavior was observed. Significant differences have been found between the maximum percentage variations observed in each BIP. During the recovery periods, an increasing trend was observed. The mean response times (time elapsed since the beginning of the period until the maximum percentage variation in the period occured) ranged between 10.116 s and 12.774 s during the BIPs, and between 11.025 s and 13.345 during the recovery periods, depending on the vessel and on the kind of BIP. © 2011 by the Massachusetts Institute of Technology.Rey Solaz, B.; Parkhutik, V.; Tembl, J.; Alcañiz Raya, ML. (2011). Breaks in Presence in Virtual Environments: An Analysis of Blood Flow Velocity Responses. Presence: Teleoperators and Virtual Environments. 20(3):273-286. doi:10.1162/PRES_a_00049S27328620

Contributions to the Development of Objective Techniques for Presence Measurement in Virtual Environments by means of Brain Activity Analysis

En esta tesis, se propone el uso de la técnica de Doppler transcraneal (DTC) para monitorizar la actividad cerebral durante la exposición a entornos virtuales (EV) y así poder analizar los correlatos cerebrales del sentido de presencia. Las hipótesis de partida son las siguientes: 1) DTC se podrá utilizar fácilmente en combinación con sistemas de realidad virtual. 2) Los datos de velocidad de flujo sanguíneo medidos por DTC se podrán utilizar para analizar cambios de actividad cerebral durante la exposición a EV. 3) Habrá diferencias en la velocidad del flujo sanguíneo asociadas a distintos niveles de presencia. 4) Habrá correlación entre el grado de presencia medido por cuestionarios y parámetros de la velocidad de flujo sanguíneo. 5) Cada componente de la experiencia virtual tendrá una influencia en las variaciones de velocidad observadas. Para analizar las hipótesis planteadas, se realizaron cuatro experimentos distintos, en los que se analizó la velocidad del flujo sanguíneo durante: 1) distintas condiciones de navegación, 2) distintas condiciones de inmersión, 3) una tarea de percepción visual y 4) tareas motoras para manejo de un joystick. Durante la tesis, se han propuesto distintas técnicas de procesado de señal basadas en análisis espectral y en la obtención parámetros no lineales de la señal, que no habían sido utilizadas previamente en experimentos psicofisiológicos con DTC. Se ha observado que existe un incremento en la velocidad del flujo sanguíneo durante la exposición a un EV, el cual puede deberse a distintos factores que intervienen en la experiencia: tareas de interacción visuoespacial, tareas de atención, la creación y ejecución de un plan motor, cambios emocionales Los análisis han mostrado que existen correlaciones significativas entre la velocidad media de flujo sanguíneo en las arterias cerebrales medias durante la exposición al EV y respuestas a los cuestionarios de presencia utilizados.Rey Solaz, B. (2010). Contributions to the Development of Objective Techniques for Presence Measurement in Virtual Environments by means of Brain Activity Analysis [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8505Palanci

Assessment of the influence of navigation control and screen size on the sense of presence in virtual reality using EEG

[EN] In the virtual reality field, presence refers to the sense of being there in the virtual world. Our aim in this work is to evaluate the usefulness of the Emotiv EPOC EEG device to measure brain activations due to the sense of presence in a virtual environment (VE), using for the analysis the sLORETA tool. We compare between three experimental conditions: photographs, video and free navigation through a VE. We also compare the differences in the sense of presence due to the visualization of the VE in different screens: a common desktop screen and a high-resolution power wall screen. We monitored 20 healthy subjects, obtaining significant differences between the navigation and video conditions in the activity of the right Insula for the Theta band. We also found a higher activation of the Insula for the Alpha and Theta bands while navigating, when comparing the two screen types. The Insula activation is related to stimulus attention and self-awareness processes, directly related with the sense of presence.This study was funded by Vicerrectorado de Investigacion de la Universitat Politecnica de Valencia, Spain, PAID-06-2011, R.N. 1984; by Ministerio de Educacion y Ciencia Spain, Project Game Teen (TIN2010-20187) and partially by projects Consolider-C (SEJ2006-14301/PSIC), "CIBER of Physiopathology of Obesity and Nutrition, an initiative of ISCIII", the Excellence Research Program PROMETEO (Generalitat Valenciana. Conselleria de Educacion, 2008-157) and the Consolider INGENIO program (CSD2007-00012). The work of Miriam Clemente was supported by the Generalitat Valenciana under a VALi+d Grant. The work of Alejandro Rodriguez was supported by the Spanish MEC under an FPI Grant BES-2011-043316.Clemente Bellido, M.; Rodríguez Ortega, A.; Rey, B.; Alcañiz Raya, ML. (2014). Assessment of the influence of navigation control and screen size on the sense of presence in virtual reality using EEG. Expert Systems with Applications. 41(4):1584-1592. https://doi.org/10.1016/j.eswa.2013.08.055S1584159241

Multimodal investigations of trans-endothelial cell trafficking under condition of disrupted blood-brain barrier integrity

<p>Abstract</p> <p>Background</p> <p>Stem cells or immune cells targeting the central nervous system (CNS) bear significant promises for patients affected by CNS disorders. Brain or spinal cord delivery of therapeutic cells is limited by the blood-brain barrier (BBB) which remains one of the recognized rate-limiting steps. Osmotic BBB disruption (BBBD) has been shown to improve small molecule chemotherapy for brain tumors, but successful delivery of cells in conjunction with BBBD has never been reported.</p> <p>We have used a clinically relevant model (pig) of BBBD to attempt brain delivery of TALL-104, a human leukemic T cell line. TALL-104 cells are potent tumor killers and have demonstrated potential for systemic tumor therapy. The pig model used is analogous to the clinical BBBD procedure. Cells were injected in the carotid artery after labeling with the MRI T1 contrast agent GdHPDO3A. Contrast CT scans were used to quantify BBBD and MRI was used to detect Gd⁺⁺-loaded cells in the brain. Transcranial Doppler was used to monitor cerebral blood flow. EEG recordings were used to detect seizures. Immunocytochemical detection (Cresyl Violet, anti-human CD8 for TALL-104, Evans Blue for BBB damage, GFAP and NEUN) was performed.</p> <p>Results</p> <p>At the concentration used TALL-104 cells were tolerated. Incomplete BBBD did not allow cell entry into the brain. MRI scans at 24 and 48 hours post-injection allowed visualization of topographically segregated cells in the hemisphere that underwent successful BBBD. Perivascular location of TALL-104 was confirmed in the BBBD hemisphere by Cresyl violet and CD8 immunocytochemistry. No significant alteration in CBF or EEG activity was recorded during cell injections.</p> <p>Conclusions</p> <p>Our data show that targeted CNS cell therapy requires blood-brain barrier disruption. MRI-detectable cytotoxic anti-neoplastic cells can be forced to transverse the BBB and accumulate in the perivascular space. The virtual absence of toxicity, the high anti-tumor activity of TALL-104, and the clinical feasibility of human osmotic BBBD suggest that this approach may be adopted to treat brain or spinal cord tumors. In addition, BBBD may favor CNS entry of other cells that normally lack CNS tropism.</p

The influence of virtual reality in e-commerce

[EN] The development of virtual reality (VR), together with other technological innovations will shape the future of e-retailing. This research studies the effectiveness of different VR formats and devices in a virtual store environment, namely V-commerce. This study proposes and test a conceptual model that analyses the relations between sense of presence, brand recall and purchase intention, while also going deeper into their antecedents. Our findings suggest differences in purchase intention depending on VR format and device used. No differences are shown in sense of presence and affect by VR format and device. Our tested model suggests a dual route of influence of VR on consumers' purchase intention in virtual stores: one through emotions and sense of presence and the other through the affect evoked by the virtual environment and brand recall. Lastly, some managerial implications and methodological issues are considered.This work has been developed by Instituto de Investigacion e Innovacion en Bioingenieria (I3B), Universitat Politecnica de Valencia and was partially supported by the Spanish Ministry of Economy, Industry and Competitiveness funded project "Advanced Therapeutically Tools for Mental Health" (DPI2016-77396-R) and the Spanish Ministry of Economy and Competitiveness, ECO2014-53837R.Martínez-Navarro, J.; Bigné-Alcañiz, E.; Guixeres Provinciale, J.; Alcañiz Raya, ML.; Torrecilla-Moreno, C. (2019). The influence of virtual reality in e-commerce. Journal of Business Research. 100:475-482. https://doi.org/10.1016/j.jbusres.2018.10.054S47548210

Cerebral Circulation

Diagnostics and diseases related to the cerebrovascular system are constantly evolving and updating. 3D augmented reality or quantification of cerebral perfusion are becoming important diagnostic tools in daily practice and the role of the cerebral venous system is being constantly revised considering new theories such as that of “the glymphatic system.” This book provides updates on models, diagnosis, and treatment of diseases of the cerebrovascular system

Revisiting the use of secondary task reaction time measures in telepresence research: exploring the role of immersion and attention

In this experimental study, we use secondary task reaction time (STRT) to measure Attention to a media presentation and compare STRT to traditional self-report measures of Telepresence (immersion, social reality, spatial presence, and transportation) and enjoyment. Further, we compare the STRT measure with the composite items of Telepresence–Immersion. The results indicate that STRT may be useful for measuring some sub-dimensions of Telepresence. Implications are discussed

Revisiting the use of secondary task reaction time measures in telepresence research: exploring the role of immersion and attention

In this experimental study, we use secondary task reaction time (STRT) to measure Attention to a media presentation and compare STRT to traditional self-report measures of Telepresence (immersion, social reality, spatial presence, and transportation) and enjoyment. Further, we compare the STRT measure with the composite items of Telepresence–Immersion. The results indicate that STRT may be useful for measuring some sub-dimensions of Telepresence. Implications are discussed