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1.
Nat Commun ; 10(1): 2732, 2019 07 02.
Artículo en Inglés | MEDLINE | ID: mdl-31266956

RESUMEN

Segregation of objects from their backgrounds is a fundamental visual function and one that is particularly effective when objects are in motion. Theoretically, suppressive center-surround mechanisms are well suited for accomplishing motion segregation. This longstanding hypothesis, however, has received limited empirical support. We report converging correlational and causal evidence that spatial suppression of background motion signals is critical for rapid segmentation of moving objects. Motion segregation ability is strongly predicted by both individual and stimulus-driven variations in spatial suppression strength. Moreover, aging-related superiority in perceiving background motion is associated with profound impairments in motion segregation. This segregation deficit is alleviated via perceptual learning, but only when motion segregation training also causes decreased sensitivity to background motion. We argue that perceptual insensitivity to large moving stimuli effectively implements background subtraction, which, in turn, enhances the visibility of moving objects and accounts for the observed link between spatial suppression and motion segregation.


Asunto(s)
Percepción de Movimiento , Navegación Espacial , Adulto , Anciano , Anciano de 80 o más Años , Envejecimiento/fisiología , Envejecimiento/psicología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Movimiento (Física) , Corteza Visual/fisiología , Adulto Joven
2.
Vision (Basel) ; 1(3)2017.
Artículo en Inglés | MEDLINE | ID: mdl-31535055

RESUMEN

Binocular rivalry is an important tool for measuring sensory eye dominance-the relative strength of sensory processing in an individual's left and right eye. By dichoptically presenting images that lack corresponding visual features, one can induce perceptual alternations and measure the relative visibility of each eye's image. Previous results indicate that observers demonstrate reliable preferences for several image features, and that these biases vary within the visual field. However, evidence about the persistence of these biases is mixed, with some suggesting they affect only the onset (i.e., first second) of rivalry, and others suggesting lasting effects during prolonged viewing. We directly investigated individuals' rivalry biases for eye and color within the visual field and interestingly found results that mirrored the somewhat contradictory pattern in the literature. Each observer demonstrated idiosyncratic patterns of biases for both color and eye within the visual field, but consistent, prolonged biases only for the eye of presentation (sensory eye dominance, SED). Furthermore, the strength of eye biases predicted one's performance on a stereoacuity task. This finding supports the idea that binocular rivalry and other binocular visual functions m ay rely on shared mechanisms, and emphasizes the importance of SED as a measure of binocular vision.

3.
Vision Res ; 141: 40-50, 2017 12.
Artículo en Inglés | MEDLINE | ID: mdl-27756700

RESUMEN

Normal binocular vision emerges from the combination of neural signals arising within separate monocular pathways. It is natural to wonder whether both eyes contribute equally to the unified cyclopean impression we ordinarily experience. Binocular rivalry, which occurs when the inputs to the two eyes are markedly different, affords a useful means for quantifying the balance of influence exerted by the eyes (called sensory eye dominance, SED) and for relating that degree of balance to other aspects of binocular visual function. However, the precise ways in which binocular rivalry dynamics change when the eyes are unbalanced remain uncharted. Relying on widespread individual variability in the relative predominance of the two eyes as demonstrated in previous studies, we found that an observer's overall tendency to see one eye more than the other was driven both by differences in the relative duration and frequency of instances of that eye's perceptual dominance. Specifically, larger imbalances between the eyes were associated with longer and more frequent periods of exclusive dominance for the stronger eye. Increases in occurrences of dominant eye percepts were mediated in part by a tendency to experience "return transitions" to the predominant eye - that is, observers often experienced sequential exclusive percepts of the dominant eye's image with an intervening mixed percept. Together, these results indicate that the often-observed imbalances between the eyes during binocular rivalry reflect true differences in sensory processing, a finding that has implications for our understanding of the mechanisms underlying binocular vision in general.


Asunto(s)
Predominio Ocular/fisiología , Visión Binocular/fisiología , Percepción Visual/fisiología , Adolescente , Adulto , Anciano , Análisis de Varianza , Femenino , Humanos , Individualidad , Masculino , Persona de Mediana Edad , Estimulación Luminosa/métodos , Adulto Joven
4.
Proc Natl Acad Sci U S A ; 113(45): 12874-12879, 2016 Nov 08.
Artículo en Inglés | MEDLINE | ID: mdl-27791061

RESUMEN

The effects of attention, as well as its functional utility, are particularly prominent when selecting among multiple stimuli that compete for processing resources. However, existing studies have found that binocular rivalry-a phenomenon characterized by perceptual competition between incompatible stimuli presented to the two eyes-is only modestly influenced by selective attention. Here, we demonstrate that the relative resistance of binocular rivalry to selective modulations gradually erodes over the course of extended perceptual training that uses a demanding, feature-based attentional task. The final result was a dramatic alteration in binocular rivalry dynamics, leading to profound predominance of the trained stimulus. In some cases, trained observers saw the trained rival image nearly exclusively throughout 4-min viewing periods. This large change in binocular rivalry predominance was driven by two factors: task-independent, eye-specific changes in visual processing, as well as an enhanced ability of attention to promote predominance of the task-relevant stimulus. Notably, this strengthening of task-driven attention also exhibited eye specificity above and beyond that from observed sensory processing changes. These empirical results, along with simulations from a recently developed model of interocular suppression, reveal that stimulus predominance during binocular rivalry can be realized both through an eye-specific boost in processing of sensory information and through facilitated deployment of attention to task-relevant features in the trained eye. Our findings highlight the interplay of attention and binocular rivalry at multiple visual processing stages and reveal that sustained training can substantially alter early visual mechanisms.

5.
Atten Percept Psychophys ; 78(7): 1861-73, 2016 10.
Artículo en Inglés | MEDLINE | ID: mdl-27230785

RESUMEN

How does attention interact with incoming sensory information to determine what we perceive? One domain in which this question has received serious consideration is that of bistable perception: a captivating class of phenomena that involves fluctuating visual experience in the face of physically unchanging sensory input. Here, some investigations have yielded support for the idea that attention alone determines what is seen, while others have implicated entirely attention-independent processes in driving alternations during bistable perception. We review the body of literature addressing this divide and conclude that in fact both sides are correct-depending on the form of bistable perception being considered. Converging evidence suggests that visual attention is required for alternations in the type of bistable perception called binocular rivalry, while alternations during other types of bistable perception appear to continue without requiring attention. We discuss some implications of this differential effect of attention for our understanding of the mechanisms underlying bistable perception, and examine how these mechanisms operate during our everyday visual experiences.


Asunto(s)
Atención , Percepción Visual , Humanos , Estimulación Luminosa
6.
Sci Rep ; 5: 11841, 2015 Jul 03.
Artículo en Inglés | MEDLINE | ID: mdl-26138079

RESUMEN

Visual phenomena demonstrating striking perceptual disappearances of salient stimuli have fascinated researchers because of their utility in identifying neural processes that underlie subjective visibility and invisibility. Motion-induced blindness (MIB) is appealing for such purposes because it, like a class of ostensibly related paradigms such as binocular rivalry, features periods of unequivocal subjective disappearances despite constant physical stimulation. It remains unclear, however, exactly how the mechanisms that cause MIB are related to subjectively observed fluctuations in visual awareness. To address this question, we used continuous flash suppression (CFS) to present the MIB stimulus outside visual awareness. Results indicated that MIB occasionally reappeared from suppression with its salient yellow target absent. To quantify this observation, we measured reaction times (RTs) to detect the yellow dot target following visible or perceptually suppressed MIB and indeed found no difference in RTs between these conditions. We also provide evidence that MIB fluctuations can occur without attention. In sum, these experiments indicate that MIB fluctuations are effectively changes in stimulus strength, which under typical conditions result in unmistakable subjective disappearances, but are not inherently fluctuations in stimulus visibility. More broadly, these results challenge the assumed privileged link between bistable stimuli and visual awareness.


Asunto(s)
Ceguera/fisiopatología , Percepción de Movimiento , Atención , Concienciación , Femenino , Humanos , Masculino , Estimulación Luminosa , Tiempo de Reacción
7.
J Vis ; 15(6): 17, 2015.
Artículo en Inglés | MEDLINE | ID: mdl-26024464

RESUMEN

Monovision presbyopia interventions exploit the binocular nature of the visual system by independently manipulating the optical properties of the two eyes. It is unclear, however, how individual variations in ocular dominance affect visual function in monovision corrections. Here, we examined the impact of sensory ocular dominance on visual performance in both traditional and modified monovision presbyopic corrections. We recently developed a binocular adaptive optics vision simulator to correct subjects' native aberrations and induce either modified monovision (1.5 D anisometropia, spherical aberration of +0.1 and -0.4 µm in distance and near eyes, respectively, over 4 mm pupils) or traditional monovision (1.5 D anisometropia). To quantify both the sign and the degree of ocular dominance, we utilized binocular rivalry to estimate stimulus contrast ratios that yield balanced dominance durations for the two eyes. Through-focus visual acuity and contrast sensitivity were measured under two conditions: (a) assigning dominant and nondominant eye to distance and near, respectively, and (b) vice versa. The results revealed that through-focus visual acuity was unaffected by ocular dominance. Contrast sensitivity, however, was significantly improved when the dominant eye coincided with superior optical quality. We hypothesize that a potential mechanism behind this observation is an interaction between ocular dominance and binocular contrast summation, and thus, assignment of the dominant eye to distance or near may be an important factor to optimize contrast threshold performance at different object distances in both modified and traditional monovision.


Asunto(s)
Predominio Ocular/fisiología , Presbiopía/fisiopatología , Presbiopía/terapia , Retina/fisiopatología , Visión Monocular/fisiología , Adulto , Lentes de Contacto , Sensibilidad de Contraste/fisiología , Femenino , Humanos , Masculino , Agudeza Visual/fisiología , Adulto Joven
8.
Atten Percept Psychophys ; 77(6): 1908-18, 2015 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-25898898

RESUMEN

Attentional influence over perception is particularly pronounced when sensory stimulation is ambiguous, where attention can reduce stimulus uncertainty and promote a stable interpretation of the world. However, binocular rivalry, an extensively studied visual ambiguity, has proved to be comparatively resistant to attentional modulation. We hypothesize that this apparent inconsistency reflects fluctuations in the degree of unresolved competition during binocular rivalry. Namely, attentional influence over rivalry dynamics should be limited to phases of relatively unresolved stimulus competition, such as ends of individual dominance periods. We found that transient, feature-based cues congruent with the dominant stimulus prolonged dominance durations, while cues matching the suppressed stimulus hastened its return to dominance. Notably, the effect of cues depended on when the cues are presented. Cues presented late, but not early, during a given episode of perceptual dominance influenced rivalry dynamics. This temporal pattern mirrors known changes in the relative competitive dynamics of rival stimuli, revealing that selective effects occur only during temporal windows containing weak resolution of visual competition. In conclusion, these findings reveal that unresolved competition, which gates attention across a variety of domains, is also crucial in determining the susceptibility of binocular rivalry to selective influences.


Asunto(s)
Atención/fisiología , Disparidad Visual/fisiología , Visión Binocular/fisiología , Señales (Psicología) , Femenino , Humanos , Masculino , Estimulación Luminosa
9.
Psychol Sci ; 25(1): 66-75, 2014 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-24171930

RESUMEN

Self-generated body movements have reliable visual consequences. This predictive association between vision and action likely underlies modulatory effects of action on visual processing. However, it is unknown whether actions can have generative effects on visual perception. We asked whether, in total darkness, self-generated body movements are sufficient to evoke normally concomitant visual perceptions. Using a deceptive experimental design, we discovered that waving one's own hand in front of one's covered eyes can cause visual sensations of motion. Conjecturing that these visual sensations arise from multisensory connectivity, we showed that grapheme-color synesthetes experience substantially stronger kinesthesis-induced visual sensations than nonsynesthetes do. Finally, we found that the perceived vividness of kinesthesis-induced visual sensations predicted participants' ability to smoothly track self-generated hand movements with their eyes in darkness, which indicates that these sensations function like typical retinally driven visual sensations. Evidently, even in the complete absence of external visual input, the brain predicts visual consequences of actions.


Asunto(s)
Movimientos Oculares/fisiología , Cinestesia/fisiología , Percepción de Movimiento/fisiología , Actividad Motora/fisiología , Trastornos de la Percepción/fisiopatología , Adulto , Femenino , Humanos , Masculino
10.
J Palliat Med ; 16(3): 289-94, 2013 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-23343113

RESUMEN

BACKGROUND: Evidence suggests palliative care consult services yield cost improvements; few studies have examined the impact of an inpatient palliative care unit on hospital costs. OBJECTIVE: This study estimates the cost avoidance of a single hospital's acute palliative care unit (APCU), building upon previous studies (1) by limiting pre-APCU costs to two days pre-APCU transfer, thereby minimizing bias from higher-cost first days of admission, and (2) by not limiting the study to cancer patients or patients who died, thereby presenting more comprehensive APCU costs. DESIGN: This retrospective study compares direct costs of care on an APCU with costs pre-APCU transfer from general medical units, intensive care units (ICU), and the emergency department (ED), and compares the direct costs of APCU patients with those of control patients. The data were entered into an SPSS(®) 17.0 (SPSS Inc., Chicago, IL) statistical software database. Paired and independent samples t-tests were conducted to test cost differences. SETTING/SUBJECTS: Study patients were admitted or transferred to the APCU from October 2008 through January 2009. Control patients were inpatients during the same time period and met several matching criteria. MEASUREMENTS: The hospital's finance department provided direct costs, case mix index (CMI), and geometric mean length of stay, and the Department of Quality and Resource Management provided patients' demographic and administrative data. RESULTS: Of 209 patients transferred to the APCU, 50% transferred from a medical unit, 32% from an ICU, and 18% from the ED. Annualized, the total cost avoidance realized by transfers to the APCU was $848,556, over half of which came from ICU to APCU transfers. CONCLUSIONS: Cost avoidance is realized when patients transfer to an APCU even when conservative pre-APCU cost measures are used and when patients with varying diagnoses and discharge outcomes are included. This study demonstrates a replicable methodology for estimating the financial impact of an APCU.


Asunto(s)
Costos de Hospital , Unidades Hospitalarias/economía , Cuidados Paliativos/economía , Anciano , Femenino , Humanos , Pacientes Internos , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Atención Terciaria de Salud/economía
11.
Front Hum Neurosci ; 5: 155, 2011.
Artículo en Inglés | MEDLINE | ID: mdl-22144958

RESUMEN

Starting from early scientific explorations of binocular rivalry, researchers have wondered about the degree to which an observer can exert voluntary attentional control over rivalry dynamics. The answer to this question would not only reveal the extent to which we may determine our own conscious visual experience, but also advance our understanding of the neural mechanisms underlying binocular rivalry. Classic studies, intriguingly, reached contradictory conclusions, ranging from an absence of attentional control, as advocated by Breese, to nearly complete control of rivalry dynamics, as reported by Helmholtz. Recent investigations have revisited this question, but the results have continued to echo the conflicting findings of earlier studies, seemingly precluding a comprehensive understanding of attentional effects on rivalry. Here, we review both classic and modern studies, and propose a unifying framework derived from the biased competition theory of attention. The key assumption of this theory is that the nature of stimulus conflict determines the limits of attentional modulation. For example, a condition in which unresolved stimulus conflict transpires through many levels of visual processing should be very susceptible to attentional control. When applied to binocular rivalry, this framework predicts strong attentional modulations under conditions of unresolved stimulus conflict (e.g., initial selection) and conditions where conflict is resolved at higher levels of visual processing (e.g., stimulus rivalry). Additionally, the efficacy of attentional control over rivalry can be increased by utilization of demanding, behaviorally relevant tasks, and likely through perceptual training paradigms. We show that this framework can help facilitate the understanding and synthesis of a diverse set of results on attentional control over rivalry, and we propose several directions for future research on this interesting topic.

12.
Am J Hosp Palliat Care ; 28(8): 528-35, 2011 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-21518705

RESUMEN

In order to graduate physicians prepared to effectively address clinical issues in palliative medicine and to comply with LCME requirements, the Northeastern Ohio Universities Colleges of Medicine and Pharmacy (NEOUCOM) integrated a coordinated four-year palliative care (PC) curriculum. This report describes the development of the longitudinal curriculum and provides helpful resources and strategies to guide clinicians and administrators undertaking similar efforts. This is a retrospective, descriptive report based on data collected throughout development of the new curriculum. A Palliative Care Advisory Committee initiated development of curricula in PC. An Office of Palliative Care was established to assess and coordinate offerings. Curriculum transformation was based on best practices. Two cornerstone pieces are highlighted: a mandatory hospice experience and a case based small group discussion prior to graduation.


Asunto(s)
Educación de Pregrado en Medicina/organización & administración , Cuidados Paliativos al Final de la Vida/métodos , Cuidados Paliativos/métodos , Aflicción , Curriculum/normas , Toma de Decisiones , Educación de Pregrado en Medicina/normas , Humanos , Comunicación Interdisciplinaria , Ohio , Relaciones Médico-Paciente , Relaciones Profesional-Familia , Desarrollo de Programa , Evaluación de Programas y Proyectos de Salud , Estudios Retrospectivos , Apoyo Social
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