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Artículos de revistas sobre el tema "Phosphene"

Autor: Grafiati

Publicado: 11 de marzo de 2023

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1

Kvašňák, E., M. Orendáčová y J. Vránová. "Phosphene Attributes Depend on Frequency and Intensity of Retinal tACS". Physiological Research 71, n.º 4 (31 de agosto de 2022): 561–71. http://dx.doi.org/10.33549/physiolres.934887.

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Phosphene is the experience of light without natural visual stimulation. It can be induced by electrical stimulation of the retina, optic nerve or cortex. Induction of phosphenes can be potentially used in assistive devices for the blind. Analysis of phosphene might be beneficial for practical reasons such as adjustment of transcranial alternating current stimulation (tACS) frequency and intensity to eliminate phosphene perception (e.g., tACS studies using verum tACS group and sham group) or, on the contrary, to maximize perception of phosphenes in order to be more able to study their dynamics. In this study, subjective reports of 50 healthy subjects exposed to different intensities of retinal tACS at 4 different frequencies (6, 10, 20 and 40 Hz) were analyzed. The effectiveness of different tACS frequencies in inducing phosphenes was at least 92 %. Subject reported 41 different phosphene types; the most common were light flashes and light circles. Changing the intensity of stimulation often induced a change in phosphene attributes. Up to nine phosphene attributes changed when the tACS intensity was changed. Significant positive correlation was observed between number of a different phosphene types and tACS frequency. Based on these findings, it can be concluded that tACS is effective in eliciting phosphenes whose type and attributes change depending on the frequency and intensity of tACS. The presented results open new questions for future research.

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Indahlastari, Aprinda, Aditya K. Kasinadhuni, Christopher Saar, Kevin Castellano, Bakir Mousa, Munish Chauhan, Thomas H. Mareci y Rosalind J. Sadleir. "Methods to Compare Predicted and Observed Phosphene Experience in tACS Subjects". Neural Plasticity 2018 (6 de diciembre de 2018): 1–10. http://dx.doi.org/10.1155/2018/8525706.

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Background. Phosphene generation is an objective physical measure of potential transcranial alternating current stimulation (tACS) biological side effects. Interpretations from phosphene analysis can serve as a first step in understanding underlying mechanisms of tACS in healthy human subjects and assist validation of computational models. Objective/Hypothesis. This preliminary study introduces and tests methods to analyze predicted phosphene occurrence using computational head models constructed from tACS recipients against verbal testimonies of phosphene sensations. Predicted current densities in the eyes and the occipital lobe were also verified against previously published threshold values for phosphenes. Methods. Six healthy subjects underwent 10 Hz tACS while being imaged in an MRI scanner. Two different electrode montages, T7-T8 and Fpz-Oz, were used. Subject ratings of phosphene experience were collected during tACS and compared against current density distributions predicted in eye and occipital lobe regions of interest (ROIs) determined for each subject. Calculated median current densities in each ROI were compared to minimum thresholds for phosphene generation. Main Results. All subjects reported phosphenes, and predicted median current densities in ROIs exceeded minimum thresholds for phosphenes found in the literature. Higher current densities in the eyes were consistently associated with decreased phosphene generation for the Fpz-Oz montage. There was an overall positive association between phosphene perceptions and current densities in the occipital lobe. Conclusions. These methods may have promise for predicting phosphene generation using data collected during in-scanner tACS sessions and may enable better understanding of phosphene origin. Additional empirical data in a larger cohort is required to fully test the robustness of the proposed methods. Future studies should include additional montages that could dissociate retinal and occipital stimulation.

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3

Et.al, Manami, K. "Investigation of Electrical Interference towards Phosphene-Based Walking Support System". Turkish Journal of Computer and Mathematics Education (TURCOMAT) 12, n.º 3 (10 de abril de 2021): 2178–83. http://dx.doi.org/10.17762/turcomat.v12i3.1164.

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A walking support system with phosphenes for blind people has been investigated. Phosphene is a phenomenon where a flash of light is recognized in the brain by giving an electrical stimulus to human’s visual pathway. Phosphenes can be perceived even if their eyes are closed or they are blind. It has been clarified that phosphenes can be induced to several directions if electrodes placements are precisely selected. When phosphenes are presented to two directions for recognizing two obstacles, two pairs of electrodes must be applied. In such a case, however, the electrical interference occurs due to the short distance between electrodes. In the practical use of the phosphene-based walking support system, the avoidance of electrical interference is significant in order to present the phosphenes precisely. Therefore, in this paper, we first practically investigate the electrical interference by considering the difference in phosphene induction generated by a single pair of electrodes and by two pairs of electrodes. Then, the solutions to avoid the electrical interference are discussed.

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4

Massumi, Brian. "Purple phosphene". Angelaki 4, n.º 3 (diciembre de 1999): 219–20. http://dx.doi.org/10.1080/09697259908572072.

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Kanamaru, Manami, Phan Xuan Tan y Eiji Kamioka. "Simulation-Based Designing of Suitable Stimulation Factors for Presenting Two Phosphenes Simultaneously to Lower Side of Field of View". Bioengineering 9, n.º 12 (2 de diciembre de 2022): 752. http://dx.doi.org/10.3390/bioengineering9120752.

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Using a phosphene has been discussed as a means of informing the visually impaired of the position of an obstacle. Obstacles underfoot have a risk, so it is necessary to inform the visually impaired. A previous study clarified a method of presenting phosphene in three directions in the lower vision; however, the simultaneous presentation of these phosphenes has not been discussed. Another study discussing the effect of electrical interference when stimulating the eyeball with multiple electrodes indicated that it is important to select appropriate stimulation factors to avoid this effect. However, when the stimulation electrodes are arranged remarkably close, there is a high possibility that the stimulus factor presented in the previous study will not apply. In this study, a method for simultaneously presenting phosphenes in the lower vision is presented. The electrode arrangements reported in the previous study to present phosphene in the lower field of vision are used, and the difficulty in the simultaneous presentation of multiple phosphenes in the lower vision is the focus. In this paper, the method of designing the stimulation factors is discussed numerically when the electrodes are arranged remarkably close. As a result, it is shown that stimulation factors different from the previous research were appropriate depending on the distance between the electrodes.

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6

Avraham, David y Yitzhak Yitzhaky. "Effects of Depth-Based Object Isolation in Simulated Retinal Prosthetic Vision". Symmetry 13, n.º 10 (22 de septiembre de 2021): 1763. http://dx.doi.org/10.3390/sym13101763.

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Visual retinal prostheses aim to restore vision for blind individuals who suffer from outer retinal degenerative diseases such as retinitis pigmentosa and age-related macular degeneration. Perception through retinal prostheses is very limited, but it can be improved by applying object isolation. We used an object isolation algorithm based on integral imaging to isolate objects of interest according to their depth from the camera and applied image processing manipulation to the isolated-object images. Subsequently, we applied a spatial prosthetic vision simulation that converted the isolated-object images to phosphene images. We compared the phosphene images for two types of input images, the original image (before applying object isolation), and the isolated-object image to illustrate the effects of object isolation on simulated prosthetic vision without and with multiple spatial variations of phosphenes, such as size and shape variations, spatial shifts, and dropout rate. The results show an improvement in the perceived shape, contrast, and dynamic range (number of gray levels) of objects in the phosphene image.

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7

Steidley, K. David. "The radiation phosphene". Vision Research 30, n.º 8 (enero de 1990): 1139–43. http://dx.doi.org/10.1016/0042-6989(90)90171-g.

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8

Nissi, Janita y Ilkka Laakso. "Magneto- and electrophosphene thresholds in the retina: a dosimetry modeling study". Physics in Medicine & Biology 67, n.º 1 (7 de enero de 2022): 015001. http://dx.doi.org/10.1088/1361-6560/ac46df.

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Abstract Objective. Sensations of flickering light produced by time-varying magnetic fields or electric currents are called magneto- or electrophosphenes. Phosphene thresholds have been used in international guidelines and standards as an estimate of the thresholds of exposure that produce effects in the central nervous system (CNS). However, the estimated threshold values have a large range of uncertainty. Approach. Phosphene thresholds were approximated by simulating five phosphene threshold experiments. Retinal electric fields and currents induced by electric and magnetic stimulation were calculated using the finite element method and 14 anatomically realistic computational models of human heads. Main results. The radial component of retinal current density was determined to be in the range of 6.0–20.6 mA m−2. This study produces more accurate estimates for threshold current density in the retina using detailed anatomical models and the estimates had a reduced range of uncertainty compared to earlier studies. Significance. The results are useful for studying the mechanisms of retinal phosphenes and for the development of exposure limits for the CNS.

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Kanamaru, Manami, Phan Xuan Tan y Eiji Kamioka. "Simulation-Based Clarification of Appropriate Factors for Presenting Phosphene in Two Directions Avoiding Electrical Interference". Bioengineering 8, n.º 8 (5 de agosto de 2021): 111. http://dx.doi.org/10.3390/bioengineering8080111.

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Walking support systems are essential for blind people. In this study, the presentation of phosphene position is focused on as a method to detect obstacles for blind people. When the phosphene is used in a walking support system, it is necessary to accurately present the phosphene in at least three directions of the visual field. Controlling the presentation of phosphene position has been reported in several previous studies. However, methodologies to present phosphene in multiple directions without any electric interference have not as yet been investigated. In this study, therefore, appropriate stimulation factors are clarified by the simulation of electric field on the eyeball surface which is strongly related to the presentation of phosphene position in the visual field. As a result of the simulation, it was revealed that the distance of each electrode does not give a significant effect to the eyeball surface. However, the phase of alternating current significantly changed the electric field on the eyeball surface. From investigation of the simulation results, it was clarified that the transition of the electric field on the eyeball surface can be controlled using anti-phase stimulation. In addition, the methodology to present the phosphene at least in two directions was verified.

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Niketeghad, Soroush, Abirami Muralidharan, Uday Patel, Jessy Dorn, Robert Greenberg y Nader Pouratian. "150 Effect of Stimulation Parameters on Visual Percepts Elicited by Stimulation of a Visual Cortical Prosthesis for the Blind". Neurosurgery 64, CN_suppl_1 (24 de agosto de 2017): 236. http://dx.doi.org/10.1093/neuros/nyx417.150.

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Abstract INTRODUCTION Stimulation of human visual cortex is known to elicit visual percepts (phosphenes) which makes it a suitable candidate for generating artificial vision for blind. Although there have been a few attempts to build visual cortical prostheses, a greater understanding of the physiology of stimulation is required to generate useful perceptions. This study aims to characterize the phosphenes elicited by a neurostimulation device and explore the effects of stimulation parameters (amplitude, frequency, pulse-width and burst duration) on the quality of these percepts. METHODS A 30-year-old volunteer with an 8-year history of bare light perception secondary to Voght-Koaynagi-Harada Syndrome participated in this study. Two parallel cortical strip leads (each with four contacts) were implanted over the right medial occipital lobe. Phosphene characteristics were assessed postoperatively using subject's drawings of on a touch screen as well as subjective description of the percepts intensity and color. The stimulus parameters for eliciting a well-defined phosphene were obtained by varying the stimulus parameters for each contact at the beginning of each session during the eight months' period of the study. RESULTS >Stimulation of each of the eight contacts elicited phosphenes with a consistent shape and location in the visual field. The stimulus parameters for generating a well-defined phosphene were stable for six contacts and had to be adjusted for two over the period of the study. Increasing the amplitude and frequency resulted in more intense perceptions and the subject indicated seeing colored phosphenes for certain amplitudes. Simultaneous stimulation of multiple contacts was perceived as a summation of percepts elicited by stimulating the contacts individually. Sequential stimulation of two contacts generated two phosphenes and the subject was able to identify them in order. CONCLUSION Visual cortical prostheses are feasible candidates for creating artificial sight due to reproducibility of the perceptions and consistency of the stimulation parameters required to generate basic visual perceptions.

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Aurora, Sheena K. y K. M. A. Welch. "Phosphene generation in migraine". Annals of Neurology 45, n.º 3 (marzo de 1999): 416. http://dx.doi.org/10.1002/1531-8249(199903)45:3<416::aid-ana28>3.0.co;2-r.

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Niketeghad, Soroush, Abirami Muralidharan, Uday Patel, Jessy D. Dorn, Laura Bonelli, Robert J. Greenberg y Nader Pouratian. "Phosphene perceptions and safety of chronic visual cortex stimulation in a blind subject". Journal of Neurosurgery 132, n.º 6 (junio de 2020): 2000–2007. http://dx.doi.org/10.3171/2019.3.jns182774.

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Stimulation of primary visual cortices has the potential to restore some degree of vision to blind individuals. Developing safe and reliable visual cortical prostheses requires assessment of the long-term stability, feasibility, and safety of generating stimulation-evoked perceptions.A NeuroPace responsive neurostimulation system was implanted in a blind individual with an 8-year history of bare light perception, and stimulation-evoked phosphenes were evaluated over 19 months (41 test sessions). Electrical stimulation was delivered via two four-contact subdural electrode strips implanted over the right medial occipital cortex. Current and charge thresholds for eliciting visual perception (phosphenes) were measured, as were the shape, size, location, and intensity of the phosphenes. Adverse events were also assessed.Stimulation of all contacts resulted in phosphene perception. Phosphenes appeared completely or partially in the left hemifield. Stimulation of the electrodes below the calcarine sulcus elicited phosphenes in the superior hemifield and vice versa. Changing the stimulation parameters of frequency, pulse width, and burst duration affected current thresholds for eliciting phosphenes, and increasing the amplitude or frequency of stimulation resulted in brighter perceptions. While stimulation thresholds decreased between an average of 5% and 12% after 19 months, spatial mapping of phosphenes remained consistent over time. Although no serious adverse events were observed, the subject experienced mild headaches and dizziness in three instances, symptoms that did not persist for more than a few hours and for which no clinical intervention was required.Using an off-the-shelf neurostimulator, the authors were able to reliably generate phosphenes in different areas of the visual field over 19 months with no serious adverse events, providing preliminary proof of feasibility and safety to proceed with visual epicortical prosthetic clinical trials. Moreover, they systematically explored the relationship between stimulation parameters and phosphene thresholds and discovered the direct relation of perception thresholds based on primary visual cortex (V1) neuronal population excitation thresholds.

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Convento, Silvia, Chiara Galantini, Nadia Bolognini y Giuseppe Vallar. "Neuromodulation of crossmodal influences on visual cortex excitability". Seeing and Perceiving 25 (2012): 149. http://dx.doi.org/10.1163/187847612x647810.

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Crossmodal interactions occur not only within brain regions deemed to be heteromodal, but also within primary sensory areas, traditionally considered as modality-specific. So far, mechanisms of crossmodal interactions in primary visual areas remain largely unknown. In the present study, we explored the effect of crossmodal stimuli on phosphene perception, induced by single-pulse transcranial magnetic stimulation (sTMS) delivered to the occipital visual cortex. In three experiments, we showed that redundant auditory and/or tactile information facilitated the detection of phosphenes induced by occipital sTMS, applied at sub-threshold intensity, which also increased their level of brightness, with the maximal enhancement occurring for trimodal stimulus combinations. Such crossmodal enhancement can be further boosted by the brain polarization of heteromodal areas mediating crossmodal links in spatial attention. Specifically, anodal transcranial direct current stimulation (tDCS) of both the occipital and the parietal cortices facilitated phosphene detection under unimodal conditions, whereas anodal tDCS of the parietal and temporal cortices enhanced phosphene detection selectively under crossmodal conditions, when auditory or tactile stimuli were combined with occipital sTMS. Overall, crossmodal interactions can enhance neural excitability within low-level visual areas, and tDCS can be used for boosting such crossmodal influences on visual responses, likely affecting mechanisms of crossmodal spatial attention involving feedback modulation from heteromodal areas on sensory-specific cortices. TDCS can effectively facilitate the integration of multisensory signals originating from the external world, hence improving visual perception.

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Gebrehiwot, Adonay N., Tatsuya Kato y Kimitaka Nakazawa. "Inducing lateralized phosphenes over the occipital lobe using transcranial magnetic stimulation to navigate a virtual environment". PLOS ONE 16, n.º 4 (14 de abril de 2021): e0249996. http://dx.doi.org/10.1371/journal.pone.0249996.

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Electrical stimulation involving visual areas of the brain produces artificial light percepts called phosphenes. These visual percepts have been extensively investigated in previous studies involving intracortical microsimulation (ICMS) and serve as the basis for developing a visual prosthesis for the blind. Although advances have been achieved, many challenges still remain with implementing a functional ICMS for visual rehabilitation purposes. Transcranial magnetic stimulation (TMS) over the primary occipital lobe offers an alternative method to produce phosphenes non-invasively. A main challenge facing blind individuals involves navigation. Within the scientific community, methods to evaluate the ability of a visual prosthesis to facilitate in navigation has been neglected. In this study, we investigate the effectiveness of evoking lateralized phosphenes to navigate a computer simulated virtual environment. More importantly, we demonstrate how virtual environments along with the development of a visual prosthesis share a mutual relationship benefiting both patients and researchers. Using two TMS devices, a pair of 40mm figure-of-eight coils were placed over each occipital hemisphere resulting in lateralized phosphene perception. Participants were tasked with making a series of left and right turns using peripheral devices depending on the visual hemifield in which a phosphene is present. If a participant was able to accurately perceive all ten phosphenes, the simulated target is able to advance and fully exit the virtual environment. Our findings demonstrate that participants can interpret lateralized phosphenes while highlighting the integration of computer based virtual environments to evaluate the capability of a visual prosthesis during navigation.

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Bolognini, Nadia, Silvia Convento, Martina Fusaro y Giuseppe Vallar. "The sound-induced phosphene illusion". Experimental Brain Research 231, n.º 4 (4 de octubre de 2013): 469–78. http://dx.doi.org/10.1007/s00221-013-3711-1.

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Bókkon, István. "Phosphene phenomenon: A new concept". Biosystems 92, n.º 2 (mayo de 2008): 168–74. http://dx.doi.org/10.1016/j.biosystems.2008.02.002.

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Bohotin, V., A. Fumai, M. Vandenheede, C. Bohotin y J. Schoenen. "Excitability of Visual V1-V2 and Motor Cortices To Single Transcranial Magnetic Stimuli in Migraine: A Reappraisal Using A Figure-Of-Eight Coil". Cephalalgia 23, n.º 4 (mayo de 2003): 264–70. http://dx.doi.org/10.1046/j.1468-2982.2003.00475.x.

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We used transcranial magnetic stimulation (TMS) with a figure-of-eight coil to excite motor and visual V1-V2 cortices in patients suffering from migraine without (MO) ( n = 24) or with aura (MA) ( n = 13) and in healthy volunteers (HV) ( n = 33). Patients who had a migraine attack within 3 days before or after the recordings were excluded. All females were recorded at mid-cycle. Single TMS pulses over the occipital cortex elicited phosphenes in 64% of HV, 63% of MO and 69% of MA patients. Compared with HV, the phosphene threshold was significantly increased in MO ( P = 0.001) and in MA ( P = 0.007), but there was no difference between the two groups of migraineurs. The motor threshold tended to be higher in both migraine groups than in HV, but the differences were not significant. In conclusion, this study shows that two-thirds (64.86%) of patients affected by either migraine type present an increased phosphene threshold in the interictal period, which suggests that their visual cortex is hypoexcitable.

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Lo, Y. L., S. L. Cui, S. Y. Lum, S. Fook Chong y H. C. Siow. "A Study of Acupuncture in Asian Patients: Clinical Aspects and Effects on Cortical Excitability". Acupuncture in Medicine 28, n.º 2 (junio de 2010): 74–77. http://dx.doi.org/10.1136/aim.2009.002055.

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Objective To determine the effect of acupuncture on the phosphene threshold, by transcranial magnetic stimulation (TMS), and the clinical effect of acupuncture on headache frequency, duration and severity. Methods Twenty-one patients (16 women; mean age 46 years; range 23–61 years, 17 Chinese, 2 Malays, 2 Indians) underwent 10 acupuncture sessions scheduled twice a week for 5 weeks. The lowest TMS intensity to elicit phosphene perception is defined as the phosphene threshold. TMS was performed before the first and last sessions, and at 2 months’ follow-up. Results Acupuncture resulted in reduction of headache frequency, duration and severity over the course of treatment. However, this was not accompanied by a corresponding increase in the phosphene threshold over a similar time course. The baseline threshold before acupuncture treatment had no predictive value for outcome of treatment. Conclusions Although acupuncture was effective in treating migraine, the use of occipital cortex excitability as an adjunctive parameter to evaluate treatment response was not suitable. The relief of migraine with acupuncture may be related to separate neural pathways independent of occipital or visual processes in the human brain.

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Tehovnik, E. J., W. M. Slocum, C. E. Carvey y P. H. Schiller. "Phosphene Induction and the Generation of Saccadic Eye Movements by Striate Cortex". Journal of Neurophysiology 93, n.º 1 (enero de 2005): 1–19. http://dx.doi.org/10.1152/jn.00736.2004.

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The purpose of this review is to critically examine phosphene induction and saccadic eye movement generation by electrical microstimulation of striate cortex (area V1) in humans and monkeys. The following issues are addressed: 1) Properties of electrical stimulation as they pertain to the activation of V1 elements; 2) the induction of phosphenes in sighted and blind human subjects elicited by electrical stimulation using various stimulation parameters and electrode types; 3) the induction of phosphenes with electrical microstimulation of V1 in monkeys; 4) the generation of saccadic eye movements with electrical microstimulation of V1 in monkeys; and 5) the tasks involved for the development of a cortical visual prosthesis for the blind. In this review it is concluded that electrical microstimulation of area V1 in trained monkeys can be used to accelerate the development of an effective prosthetic device for the blind.

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Smith, Daniel T., Keira Ball y Amanda Ellison. "Inhibition of Return Impairs Phosphene Detection". Journal of Cognitive Neuroscience 24, n.º 11 (noviembre de 2012): 2262–67. http://dx.doi.org/10.1162/jocn_a_00276.

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Efficient visual exploration requires the ability to select possible target locations via spatial attention and to deselect previously inspected locations via inhibition of return (IOR). Although a great deal is known about the effects of spatial attention on processing in visual cortex, much less is known about the effects of IOR on early visual areas. One possibility is that IOR acts in an opposite way to spatial attention, such that, whereas spatial attention enhances target related neural signals in visual cortex, IOR suppress target-related signals. Using a novel dual-coil TMS protocol, we found that IOR reduced the probability of detecting a TMS-induced phosphene in extrastriate cortex (V5). Specifically, a nonpredictive spatial precue presented 500 or 800 msec before stimulation significantly reduced the probability of detecting a phosphene when the precue appeared contralaterally to the site of stimulation (i.e., ipsilaterally to the potential location of the phosphene), compared with ipsilaterally or centrally presented cues. This result demonstrates that IOR facilitates visual exploration by directly affecting the strength of target-related signals in extrastriate visual cortex. This result is consistent with neurophysiological models of attention, which postulate that IOR modulates perception by biasing competition between sensory representations.

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Engmann, Birk. "Phosphene und Photopsien – Okzipitallappeninfarkt oder Reizdeprivation?" Zeitschrift für Neuropsychologie 19, n.º 1 (enero de 2008): 7–13. http://dx.doi.org/10.1024/1016-264x.19.1.7.

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Bei einer 85-jährigen Frau stellte sich apoplektiform eine Sehverschlechterung einhergehend mit Phosphenen, Photopsien und pedunkulären Halluzinationen ohne Quadranten- oder Hemianopsie ein. Neben einer ischämischen Genese bei im MRT nachgewiesener subkortikaler vaskulärer Enzephalopathie und kortikalen Läsionen im Bereich der Okzipitallappenpole wird eine ophthalmopathische Halluzinose im Sinne eines Charles- Bonnet- Syndroms bei Reizdeprivation infolge Optikusatrophie und Makuladegeneration diskutiert. Mit der Falldarstellung soll die Bedeutung der Differentialdiagnose halluzinatorischer Phänomene bei älteren Menschen zu psychiatrischen Erkrankungen und dementiellen Syndromen verdeutlicht werden, da sich daraus unterschiedliche medikamentöse Konsequenzen ergeben könnten.

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Park, J., D. A. Wu y S. Shimojo. "Perisaccadic localization of TMS-induced phosphene". Journal of Vision 6, n.º 6 (24 de marzo de 2010): 867. http://dx.doi.org/10.1167/6.6.867.

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Taylor, Paul C. J., Vincent Walsh y Martin Eimer. "The neural signature of phosphene perception". Human Brain Mapping 31, n.º 9 (17 de agosto de 2010): 1408–17. http://dx.doi.org/10.1002/hbm.20941.

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Chen, Xing, Feng Wang, Eduardo Fernandez y Pieter R. Roelfsema. "Shape perception via a high-channel-count neuroprosthesis in monkey visual cortex". Science 370, n.º 6521 (3 de diciembre de 2020): 1191–96. http://dx.doi.org/10.1126/science.abd7435.

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Blindness affects 40 million people across the world. A neuroprosthesis could one day restore functional vision in the blind. We implanted a 1024-channel prosthesis in areas V1 and V4 of the visual cortex of monkeys and used electrical stimulation to elicit percepts of dots of light (called phosphenes) on hundreds of electrodes, the locations of which matched the receptive fields of the stimulated neurons. Activity in area V4 predicted phosphene percepts that were elicited in V1. We simultaneously stimulated multiple electrodes to impose visible patterns composed of a number of phosphenes. The monkeys immediately recognized them as simple shapes, motions, or letters. These results demonstrate the potential of electrical stimulation to restore functional, life-enhancing vision in the blind.

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Zhao, Ying, Yanyu Lu, Chuanqing Zhou, Yao Chen, Qiushi Ren y Xinyu Chai. "Chinese Character Recognition Using Simulated Phosphene Maps". Investigative Opthalmology & Visual Science 52, n.º 6 (20 de mayo de 2011): 3404. http://dx.doi.org/10.1167/iovs.09-4234.

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Chew, G. S. M., G. F. Sanderson y A. C. B. Molteno. "The pressure phosphene tonometer—a clinical evaluation". Eye 19, n.º 6 (11 de junio de 2004): 683–85. http://dx.doi.org/10.1038/sj.eye.6701600.

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Leung, D. Y. L. y D. S. C. Lam. "The proview phosphene tonometer: a clinical evaluation". Eye 19, n.º 11 (29 de octubre de 2004): 1227. http://dx.doi.org/10.1038/sj.eye.6701735.

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Fresco, Bernard B. "A new tonometer—the pressure phosphene tonometer". Ophthalmology 105, n.º 11 (noviembre de 1998): 2123–26. http://dx.doi.org/10.1016/s0161-6420(98)91137-x.

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Tehovnik, Edward J. y Warren M. Slocum. "Phosphene induction by microstimulation of macaque V1". Brain Research Reviews 53, n.º 2 (febrero de 2007): 337–43. http://dx.doi.org/10.1016/j.brainresrev.2006.11.001.

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Renzi, Chiara, Tomaso Vecchi, Egidio D’ Angelo, Juha Silvanto y Zaira Cattaneo. "Phosphene induction by cerebellar transcranial magnetic stimulation". Clinical Neurophysiology 125, n.º 10 (octubre de 2014): 2132–33. http://dx.doi.org/10.1016/j.clinph.2014.01.031.

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31

Ahmad, Hena, Richard Roberts, Qadeer Arshad Arshad, Mitesh Patel y Adolfo Bronstein. "USING TRANSCRANIAL MAGNETIC STIMULATION (TMS) TO PROBE EFFECTS OF VISUAL MOTION ADAPTATION ON PRIMARY VISUAL CORTEX (V1) EXCITABILITY IN BILATERAL VESTIBULAR FAILURE (BVF) PATIENTS". Journal of Neurology, Neurosurgery & Psychiatry 86, n.º 11 (14 de octubre de 2015): e4.70-e4. http://dx.doi.org/10.1136/jnnp-2015-312379.161.

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Background and aimPatients with BVF report oscillopsia due to a defective vestibulo-ocular reflex causing retinal slip. No previous studies have probed visual cortical excitability using TMS and visual motion processing in these patients. We investigated the effects of visual motion adaptation on V1 cortical excitability in BVF patients and correlated this with psychophysical parameters.Methods12 BVF patients (7 males) aged 29–65 (mean=54.5) and 12 controls (6 males) aged 42–73 (mean=55) were recruited. Biphasic TMS pulses were applied at V1 and phosphene threshold (PT) was estimated. 3 measurement phases were (1) Stationary (2) Motion with optokinetic stimulation (OKS) Adaptation: OKS rightwards for 5 minutes 3) Post adaptation during viewing motion. All subjects completed questionnaires prior to the experiment. Results were analysed offline by calculating the probability of phosphene perception.ResultsBaseline phosphene thresholds were significantly higher in BVF patients (p=0.024) reflecting reduced visual cortical excitability. Lower oscillopsia scores correlated with reduced baseline V1 excitability (p=0.009).ConclusionsThis novel finding acts as a neurophysiological correlate for clinical observations of adaptive visual motion perception and is also correlated with psychophysical parameters. These results provide evidence for adaptive mechanisms leading to cortical plasticity following BVF.

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32

Császár, Noémi, Felix Scholkmann, Vahid Salari, Henrik Szőke y István Bókkon. "Phosphene perception is due to the ultra-weak photon emission produced in various parts of the visual system: glutamate in the focus". Reviews in the Neurosciences 27, n.º 3 (1 de abril de 2016): 291–99. http://dx.doi.org/10.1515/revneuro-2015-0039.

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AbstractPhosphenes are experienced sensations of light, when there is no light causing them. The physiological processes underlying this phenomenon are still not well understood. Previously, we proposed a novel biopsychophysical approach concerning the cause of phosphenes based on the assumption that cellular endogenous ultra-weak photon emission (UPE) is the biophysical cause leading to the sensation of phosphenes. Briefly summarized, the visual sensation of light (phosphenes) is likely to be due to the inherent perception of UPE of cells in the visual system. If the intensity of spontaneous or induced photon emission of cells in the visual system exceeds a distinct threshold, it is hypothesized that it can become a conscious light sensation. Discussing several new and previous experiments, we point out that the UPE theory of phosphenes should be really considered as a scientifically appropriate and provable mechanism to explain the physiological basis of phosphenes. In the present paper, we also present our idea that some experiments may support that the cortical phosphene lights are due to the glutamate-related excess UPE in the occipital cortex.

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Romei, Vincenzo, Micah M. Murray, Céline Cappe y Gregor Thut. "The Contributions of Sensory Dominance and Attentional Bias to Cross-modal Enhancement of Visual Cortex Excitability". Journal of Cognitive Neuroscience 25, n.º 7 (julio de 2013): 1122–35. http://dx.doi.org/10.1162/jocn_a_00367.

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Approaching or looming sounds (L-sounds) have been shown to selectively increase visual cortex excitability [Romei, V., Murray, M. M., Cappe, C., & Thut, G. Preperceptual and stimulus-selective enhancement of low-level human visual cortex excitability by sounds. Current Biology, 19, 1799–1805, 2009]. These cross-modal effects start at an early, preperceptual stage of sound processing and persist with increasing sound duration. Here, we identified individual factors contributing to cross-modal effects on visual cortex excitability and studied the persistence of effects after sound offset. To this end, we probed the impact of different L-sound velocities on phosphene perception postsound as a function of individual auditory versus visual preference/dominance using single-pulse TMS over the occipital pole. We found that the boosting of phosphene perception by L-sounds continued for several tens of milliseconds after the end of the L-sound and was temporally sensitive to different L-sound profiles (velocities). In addition, we found that this depended on an individual's preferred sensory modality (auditory vs. visual) as determined through a divided attention task (attentional preference), but not on their simple threshold detection level per sensory modality. Whereas individuals with “visual preference” showed enhanced phosphene perception irrespective of L-sound velocity, those with “auditory preference” showed differential peaks in phosphene perception whose delays after sound-offset followed the different L-sound velocity profiles. These novel findings suggest that looming signals modulate visual cortex excitability beyond sound duration possibly to support prompt identification and reaction to potentially dangerous approaching objects. The observed interindividual differences favor the idea that unlike early effects this late L-sound impact on visual cortex excitability is influenced by cross-modal attentional mechanisms rather than low-level sensory processes.

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34

Dagnelie, G., V. T. Yin, D. Hess y L. Yang. "Phosphene mapping strategies for cortical visual prosthesis recipients". Journal of Vision 3, n.º 9 (16 de marzo de 2010): 222. http://dx.doi.org/10.1167/3.9.222.

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35

Abrahamyan, Arman, Colin W. G. Clifford, Manuela Ruzzoli, Dan Phillips, Ehsan Arabzadeh y Justin A. Harris. "Accurate and Rapid Estimation of Phosphene Thresholds (REPT)". PLoS ONE 6, n.º 7 (22 de julio de 2011): e22342. http://dx.doi.org/10.1371/journal.pone.0022342.

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36

Oswalt, Denise, William Bosking, Ping Sun, Sameer A. Sheth, Soroush Niketeghad, Michelle Armenta Salas, Uday Patel et al. "Multi-electrode stimulation evokes consistent spatial patterns of phosphenes and improves phosphene mapping in blind subjects". Brain Stimulation 14, n.º 5 (septiembre de 2021): 1356–72. http://dx.doi.org/10.1016/j.brs.2021.08.024.

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37

Kanamaru, Manami, Phan Xuan Tan y Eiji Kamioka. "Design of Electrode Placement for Presenting Phosphenes in the Lower Visual Field Based on Electric Field Simulation". Applied Sciences 11, n.º 22 (19 de noviembre de 2021): 10972. http://dx.doi.org/10.3390/app112210972.

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Presenting visual information, called phosphenes, is a critical method for providing information on the position of obstacles for users of walking support tools for the visually impaired. A previous study has established a method for presenting phosphenes to the right, center, and left of the visual field. However, a method for presenting information on the position of obstacles around the feet using phosphenes, which is essential for the visually impaired, has not been clarified. Therefore, in this study, a method for presenting phosphenes in the lower visual field is presented, towards the aim of realizing a safe walking support tool. Electrode placement is proposed in this paper for the presentation of phosphenes to the right, center, and left of the lower visual field based on the electrode placement method used in the previous study, which presents the phosphene in three locations of the visual field. In addition, electric field simulation is performed, focusing on the electric field value on the eyeball surface, in order to observe whether the proposed electrode placement is able to stimulate the intended region. As a result, it is shown that the intended region on the eyeball surface can be stimulated locally with each of the proposed electrode placements.

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38

Morledge-Hampton, Scott J., Robert O. Kwon, Rohit Krishna, Peter W. Debry y Thomas L. Willoughby. "Comparison of Proview phosphene tonometry with Goldmann applanation tonometry". Canadian Journal of Ophthalmology 41, n.º 6 (diciembre de 2006): 722–26. http://dx.doi.org/10.3129/i06-065.

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39

Rangelov, Dragan, Hermann J. Müller y Paul C. J. Taylor. "Occipital TMS at phosphene detection threshold captures attention automatically". NeuroImage 109 (abril de 2015): 199–205. http://dx.doi.org/10.1016/j.neuroimage.2015.01.035.

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40

Obeid, Iyad, Claude Veraart y Jean Delbeke. "Estimation of Phosphene Spatial Variability for Visual Prosthesis Applications". Artificial Organs 34, n.º 5 (mayo de 2010): 358–65. http://dx.doi.org/10.1111/j.1525-1594.2009.00878.x.

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41

Lu, Yanyu, Panpan Chen, Ying Zhao, Jingru Shi, Qiushi Ren y Xinyu Chai. "Estimation of Simulated Phosphene Size Based on Tactile Perception". Artificial Organs 36, n.º 1 (2 de agosto de 2011): 115–20. http://dx.doi.org/10.1111/j.1525-1594.2011.01288.x.

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42

Kammer, Thomas y Lisa W. Baumann. "Phosphene thresholds evoked with single and double TMS pulses". Clinical Neurophysiology 121, n.º 3 (marzo de 2010): 376–79. http://dx.doi.org/10.1016/j.clinph.2009.12.002.

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43

Franca, Michele, Giacomo Koch, Hitoshi Mochizuki, Ying-Zu Huang y John C. Rothwell. "Effects of theta burst stimulation protocols on phosphene threshold". Clinical Neurophysiology 117, n.º 8 (agosto de 2006): 1808–13. http://dx.doi.org/10.1016/j.clinph.2006.03.019.

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44

Ramos-Estebanez, C., L. B. Merabet, K. Machii, F. Fregni, G. Thut, T. A. Wagner, V. Romei, A. Amedi y A. Pascual-Leone. "Visual Phosphene Perception Modulated by Subthreshold Crossmodal Sensory Stimulation". Journal of Neuroscience 27, n.º 15 (11 de abril de 2007): 4178–81. http://dx.doi.org/10.1523/jneurosci.5468-06.2007.

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45

Chadaide, Z., S. Arlt, A. Antal, MA Nitsche, N. Lang y W. Paulus. "Transcranial Direct Current Stimulation Reveals Inhibitory Deficiency In Migraine". Cephalalgia 27, n.º 7 (julio de 2007): 833–39. http://dx.doi.org/10.1111/j.1468-2982.2007.01337.x.

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The issue of interictal excitability of cortical neurons in migraine patients is controversial: some studies have reported hypo-, others hyperexcitability. The aim of the present study was to observe the dynamics of this basic interictal state by further modulating the excitability level of the visual cortex using transcranial direct current stimulation (tDCS) in migraineurs with and without aura. In healthy subjects anodal tDCS decreases, cathodal stimulation increases transcranial magnetic stimulation (TMS)-elicited phosphene thresholds (PT), which is suggested as a representative value of visual cortex excitability. Compared with healthy controls, migraine patients tended to show lower baseline PT values, but this decrease failed to reach statistical significance. Anodal stimulation decreased phosphene threshold in migraineurs similarly to controls, having a larger effect in migraineurs with aura. Cathodal stimulation had no significant effect in the patient groups. This result strengthens the notion of deficient inhibitory processes in the cortex of migraineurs, which is selectively revealed by activity-modulating cortical input.

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46

Lubeck, Astrid J. A., Angelique Van Ombergen, Hena Ahmad, Jelte E. Bos, Floris L. Wuyts, Adolfo M. Bronstein y Qadeer Arshad. "Differential effect of visual motion adaption upon visual cortical excitability". Journal of Neurophysiology 117, n.º 3 (1 de marzo de 2017): 903–9. http://dx.doi.org/10.1152/jn.00655.2016.

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The objectives of this study were 1) to probe the effects of visual motion adaptation on early visual and V5/MT cortical excitability and 2) to investigate whether changes in cortical excitability following visual motion adaptation are related to the degree of visual dependency, i.e., an overreliance on visual cues compared with vestibular or proprioceptive cues. Participants were exposed to a roll motion visual stimulus before, during, and after visual motion adaptation. At these stages, 20 transcranial magnetic stimulation (TMS) pulses at phosphene threshold values were applied over early visual and V5/MT cortical areas from which the probability of eliciting a phosphene was calculated. Before and after adaptation, participants aligned the subjective visual vertical in front of the roll motion stimulus as a marker of visual dependency. During adaptation, early visual cortex excitability decreased whereas V5/MT excitability increased. After adaptation, both early visual and V5/MT excitability were increased. The roll motion-induced tilt of the subjective visual vertical (visual dependence) was not influenced by visual motion adaptation and did not correlate with phosphene threshold or visual cortex excitability. We conclude that early visual and V5/MT cortical excitability is differentially affected by visual motion adaptation. Furthermore, excitability in the early or late visual cortex is not associated with an increase in visual reliance during spatial orientation. Our findings complement earlier studies that have probed visual cortical excitability following motion adaptation and highlight the differential role of the early visual cortex and V5/MT in visual motion processing. NEW & NOTEWORTHY We examined the influence of visual motion adaptation on visual cortex excitability and found a differential effect in V1/V2 compared with V5/MT. Changes in visual excitability following motion adaptation were not related to the degree of an individual's visual dependency.

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Fan, Dorothy S. P., Thomas Y. H. Chiu, Nathan Congdon, Jeffrey C. W. Chan, Eva Y. Y. Cheung y Dennis S. C. Lam. "Measurement of Intraocular Pressure with Pressure Phosphene Tonometry in Children". Journal of Pediatric Ophthalmology & Strabismus 48, n.º 3 (23 de junio de 2010): 167–73. http://dx.doi.org/10.3928/01913913-20100618-02.

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48

Young, William B., Michael L. Oshinsky, Aaron L. Shechter, Cheryl Gebeline-Myers, Kathleen C. Bradley y Eric M. Wassermann. "Consecutive Transcranial Magnetic Stimulation: Phosphene Thresholds in Migraineurs and Controls". Headache: The Journal of Head and Face Pain 44, n.º 2 (febrero de 2004): 131–35. http://dx.doi.org/10.1111/j.1526-4610.2004.04028.x.

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49

Webster, Kelly y Tony Ro. "Phosphene perception from transcranial magnetic stimulation (TMS) over the vertex". Journal of Vision 16, n.º 12 (1 de septiembre de 2016): 1142. http://dx.doi.org/10.1167/16.12.1142.

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Naruse, Shigeta, Kazuhiko Mori y Shigeru Kinoshita. "Evaluation of the pressure phosphene tonometer as a self-tonometer". Ophthalmic and Physiological Optics 25, n.º 5 (septiembre de 2005): 421–28. http://dx.doi.org/10.1111/j.1475-1313.2005.00311.x.

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