In sum, this is the first known neuroimaging study including children with single and double deficits to find evidence of dissociation in brain systems subserving phonological and rapid naming processing, although the findings are in line with previous research that shows unique brain activations associated with PA versus RAN abilities (). Dissociations in brain activations were observed in multiple analyses, including functional activation in ROIs and the whole brain, as well as functional connectivity. Our study suggests that children with a double deficit have the greatest reduction in brain activation in regions important for both rapid naming skills and phonological awareness, even when compared with children who have single deficits. These findings have implications both for the design of future neuroimaging studies and also for the design of assessment batteries, diagnostic criteria, and educational interventions, as children meeting different criteria for reading impairment also show differential brain activation and behavioral profiles.
One way of assessing the presence of an automaticity deficit is through the use of a rapid automatised naming task (RAN). For example, individuals may be presented with a set of 50 stimuli consisting of five rows of 10 pictures of a given type in a random order and asked to name each picture as quickly as possible (see Figure 3). People with dyslexia typically show a deficit in speed on this type of task.
The word retrieval deficit hypothesis and developmental dyslexia .
Deficits in PA alone do not account for all cases of dyslexia (e.g., ). Rapid automatized naming (RAN) deficits are also evident in a subset of individuals with developmental dyslexia (; ; ; ; ). RAN, sometimes referred to as naming speed or rapid naming, is the speed with which one can name visually-presented familiar stimuli such as letters, numbers, colors and objects out loud (), and reflects the automaticity of processes which are also important for reading ().
We examined the double-deficit hypothesis in Finnish
These results have been interpreted as further support for a phonological deficit in reading, as the task does require some phonological processing during the retrieval of the picture names. However, more recently Wolf and Bowers (1999) have suggested that difficulties in rapid naming are a separate, additional deficit to phonological difficulties, and that such a deficit is sufficient to explain reading difficulties even if the person has good phonological awareness. They suggest that people with reading difficulties fall into one of three subtypes, depending on the underlying cause of their problem:
The double-deficit hypothesis: a comprehensive …
I think Wolfe is going beyond asking a question about the role vision plays in double deficit hypothesis and is providing a theory of how it is involved. Other researchers, as the article discusses, do not necessarily agree with her theory.
, the so called double-deficit hypothesis.
There is actually significant research to support this theory. One only has to pull up the research of Prof Stein that I posted a few times and read his work along with the work his references. The critisism that the auditory only crowd consistantly site is that the correlation between an improvement in binocular vision associated with an improvement in reading is a result of the reading skill improving the vision. They don't accept that both vision and auditory deficits could be playing a role in the reading dysfunction.