Are visual attention deficits in dyslexia reading-specific? A combined eye-tracking/fMRI investigation.

Brigham Young University, Provo UT

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Abstract

Project Summary Dyslexia is a learning disorder that impairs reading in childhood and throughout life. This is, at least in part, because of language-related problems in dyslexia. However, it is currently unclear if dyslexia is solely a language-based disorder or if there are other deficits as well. When dyslexic individuals read, their eye movements differ from readers without dyslexia, indicating decreased visual attention efficiency. More specifically, research suggests that dyslexic readers have a narrower ?attentional spotlight? when they read, meaning that they extract useful information from a smaller section of the text than do typical readers. This deficit in visual attention may be caused by an underlying language deficit or may be partly independent of the language deficit ? the current literature is unclear. The purpose of this research is to reveal whether visual attention deficits are independent of language deficits in dyslexia or not. This will be accomplished by comparing eye movements (which reflect visual attention) in reading and in visual tasks, such as memorizing a picture or searching for an object in a photograph, that do not involve language. A group of adult participants with dyslexia and a group of control participants will perform these tasks while their eye movements are monitored. In the first experiment, visual information will be restricted using a ?moving window? of different sizes. This technique helps define the size of the attentional spotlight, which is the smallest window that causes no change in eye movements compared to a no-window control condition. If the visual attention deficit in dyslexia is not entirely caused by the language deficit, then visual attention problems should be apparent, in the form of a narrower attentional spotlight, in the language-free tasks as well as in reading. On the other hand, if the visual attention deficit is solely caused by the language deficit, then the eye movements of dyslexics should only differ from controls in the reading task. These same participants will also perform reading and scene memorization tasks while their eyes are tracked and their brains are being scanned (fMRI) in order to identify the cortical network involved in visual attention and the specific brain regions within this network that are impaired in dyslexia. If dyslexia is primarily a language disorder, then only reading-specific cortical areas should be differentially active in dyslexic participants, and no activation differences should be observed during the scene memorization task. Finally, these eye-tracking and neuroimaging data will be used in combination with scores on a battery of standardized language tasks to identify which aspects of language (phonology, vocabulary, fluency) are predictive of visual attention and to quantify the extent to which attentional problems in dyslexia are dependent on language deficits. This knowledge will help focus interventions and treatments for dyslexia.