RESUMEN
Human visual experience of objects comprises a combination of visual features, such as color, position, and shape. Spatial attention is thought to play a role in creating a coherent perceptual experience, integrating visual information coming from a given location, but the mechanisms underlying this process are not fully understood. Deficits of spatial attention in which this integration process does not occur normally, such as neglect, can provide insights regarding the mechanisms of spatial attention in visual object recognition. In this study, we describe a series of experiments conducted with an individual with neglect, DH. DH presents characteristic lack of awareness of the left side of individual objects, evidenced by poor object and face recognition, and impaired word reading. However, he exhibits intact recognition of color within the boundaries of the same objects he fails to recognize. Furthermore, he can also report the orientation and location of a colored region on the neglected left side despite lack of awareness of the shape of the region. Overall, DH shows selective lack of awareness of shape despite intact processing of basic visual features in the same spatial location. DH's performance raises intriguing questions and challenges about the role of spatial attention in the formation of coherent object percepts and visual awareness.
Asunto(s)
Atención , Concienciación , Trastornos de la Percepción , Humanos , Masculino , Trastornos de la Percepción/fisiopatología , Atención/fisiología , Concienciación/fisiología , Reconocimiento Visual de Modelos/fisiología , Percepción Visual/fisiología , Percepción Espacial/fisiología , Estimulación Luminosa/métodos , Reconocimiento en Psicología/fisiología , Persona de Mediana Edad , Percepción de Forma/fisiología , AncianoRESUMEN
Visual awareness is thought to result from integration of low- and high-level processing; instances of integration failure provide a crucial window into the cognitive and neural bases of awareness. We present neurophysiological evidence of complex cognitive processing in the absence of awareness, raising questions about the conditions necessary for visual awareness. We describe an individual with a neurodegenerative disease who exhibits impaired visual awareness for the digits 2 to 9, and stimuli presented in close proximity to these digits, due to perceptual distortion. We identified robust event-related potential responses indicating 1) face detection with the N170 component and 2) task-dependent target-word detection with the P3b component, despite no awareness of the presence of faces or target words. These data force us to reconsider the relationship between neural processing and visual awareness; even stimuli processed by a workspace-like cognitive system can remain inaccessible to awareness. We discuss how this finding challenges and constrains theories of visual awareness.
Asunto(s)
Cognición/fisiología , Potenciales Evocados/fisiología , Trastornos de la Visión/metabolismo , Percepción Visual/fisiología , Concienciación/fisiología , Encéfalo/fisiología , Electroencefalografía , Potenciales Evocados Visuales/fisiología , Cara , Femenino , Humanos , Masculino , Persona de Mediana Edad , Enfermedades Neurodegenerativas , Estimulación Luminosa , Corteza Visual/fisiologíaRESUMEN
Beginning with Dejerine's report of pure alexia in 1892, numerous researchers have noted that individuals with acquired impairments of reading may show spared digit identification performance. This digit advantage has also been found in unimpaired adult readers across a number of tasks, and five main hypotheses have been proposed to explain how it arises. In this paper I consider these hypotheses in the context of recent theories of a unified alphanumeric character identification system, and evaluate them according to relevant empirical evidence. Despite some promising findings, none of the hypotheses currently provide a sufficient explanation of the digit advantage. Rather than developing new hypotheses to explain a categorical difference between digit and letter performance, I argue that future work should consider factors that affect identification performance specific to individual characters.
Asunto(s)
Dislexia Adquirida/psicología , Conceptos Matemáticos , Reconocimiento Visual de Modelos , Lectura , Dislexia Adquirida/diagnóstico por imagen , Dislexia Adquirida/fisiopatología , Humanos , Modelos Psicológicos , Reconocimiento Visual de Modelos/fisiologíaRESUMEN
In 2008 Christian Boer, a Dutch artist, developed a special font ("Dyslexie") to facilitate reading in children and adults with dyslexia. The font has received a lot of media attention worldwide (e.g., TheGuardian.com, Slate.com, TheAtlantic.com, USA Today, and io9.com). Interestingly, there is barely any empirical evidence for the efficacy of Dyslexie. This study aims to examine if Dyslexie is indeed more effective than a commonly used sans serif font (Arial) and, if so, whether this can be explained by its relatively large spacing settings. Participants were 39 low-progress readers who were learning to read in English. They were asked to read four different texts in four different font conditions that were all matched on letter display size (i.e., x-height), but differed in the degree to which they were matched for spacing settings. Results showed that low-progress readers performed better (i.e., read 7% more words per minute) in Dyslexie font than in standardly spaced Arial font. However, when within-word spacing and between-word spacing of Arial font was matched to that of Dyslexie font, the difference in reading speed was no longer significant. We concluded that the efficacy of Dyslexie font is not because of its specially designed letter shapes, but because of its particular spacing settings. Copyright © 2016 John Wiley & Sons, Ltd.