User:Karen Monuszko/sandbox

"Classification" section edit Deep dyslexia was previously regarded as a form of acquired dyslexia as opposed to a developmental dyslexia. Cases of developmental deep dyslexia were rare. However, recently, developmental deep dyslexia has been more frequently reported in children with Williams Syndrome. Deep dyslexia is considered to be a “central” dyslexia in which deep aspects of reading are compromised as opposed to the visual stimulus processing deficits in “peripheral” dyslexias. Deep dyslexia differs from other forms of central dyslexia (phonological dyslexia and surface dyslexia) in that deep dyslexics have many more symptoms and these symptoms are generally more severe. According to the “continuum” hypothesis, deep dyslexia is just a more severe progression of phonological dyslexia.

"Signs and Symptoms" section edit Deep dyslexia is mainly characterised by the occurrence of semantic reading errors or semantic paralexias when reading aloud (e.g. view → “scene“, bird → “canary”). These semantic errors are the major distinguishing feature of deep dyslexia in comparison to other central dyslexias. Other characteristics of deep dyslexia include visual errors (e.g. thing → “think”, skate → “scale”) and deviational errors (e.g. alcohol → alcoholic, governor → government) as well as poor reading of function words, more difficulty reading abstract than concrete and highly imaginable words, more difficulty reading adjectives, adverbs, and verbs than nouns, a complete inability to read non-words, severe impairments when writing to diction and writing spontaneously, and in many cases an impairment in short term memory, or digit span. While the symptoms of deep dyslexia are different and independent impairments of reading, it is rare to find an individual who only displays some of the characteristics of it; indeed, most patients presenting with semantic paralexias also demonstrate all of the other symptoms. This has resulted in deep dyslexia being considered a symptom-complex and has led to much research into why this variety of symptoms may co-occur in so many patients. The difficulty of deep dyslexics in reading abstract words has been referred to as the imageability effect. According to this theory, the ease with which a mental image can be created for a word is directly related to the ease of reading the word. Given that the “imageability” of a word is an obscure variable to measure, researchers have developed a new variable which is measureable and more directly related to the cognitive system. This variable, ease of predication, refers to a rating of how easy it is to come up with simple factual statements or attributes of a word. Deep dyslexics use imagery or a predicational route in reading to compromise for the deficient and more precise mechanisms used in normal reading. Thus, ease of predication has been shown to be an accurate measurement of some of the reading difficulties seen in deep dyslexia.

"Theories and Hypotheses" new section There is a wide variety of hypotheses that attempt to explain the deficits associated with deep dyslexia. Further research needs to be performed to obtain more conclusive information regarding this condition. Two main approaches attempt to explain the reading deficits characteristic of deep dyslexia. Normal reading is typically a function of a left hemisphere-based system. The right hemisphere plays a minimal role in reading. One hypothesis, the left-hemisphere hypothesis, supports the idea of a damaged left hemisphere-based reading system associated with deep dyslexia. Deep dyslexics may be attempting to use this damaged left hemisphere, resulting in severe reading deficits. On the other hand, the right-hemisphere hypothesis states that deep dyslexics attempt to read using a completely different reading system. According to this hypothesis, they are using a right hemisphere system to read, but given that this system does not usually play a role in reading, many functions of reading are compromised. In addition to the right versus left hemisphere debate, researchers also disagree upon whether deep dyslexia is a result of processing deficits or production (reading aloud) deficits. Some researchers believe that deep dyslexia arises from problems in sub-word, or sub-lexical, processing. Additionally, two other processing “modules” are affected. It is believed that patients have a partially functioning lexical module, and a completely deficient nonlexical module. The lexical module relies on lexical memory, or the memory for words, to name words. The nonlexical module uses knowledge of spelling and graphemes to create phonemes to name words and nonwords. The absent nonlexical module in deep dyslexics explains why patients cannot name nonwords. However, the idea that deep dyslexics have poor processing of phonology is contradicted by studies that show effects of implicit phonological knowledge on the reading abilities of patients. Thus, some researchers believe that the impairments present are only in explicit phonological output (i.e., reading aloud), and not in processing. They believe that the problems of deep dyslexics are due to production errors, and that deep dyslexics have normal phonological processing at the implicit level. This is supported by the fact that deep dyslexia is often present in patients with Broca’s aphasia. The impairment in the explicit task of production is believed to be due to failure of inhibition. The failure of inhibition hypothesis is associated with the lexical module discussed earlier. The presentation of a word activates lexical memory of that word, along with other words that are semantically related. For example, the target word “dog” may activate “bark”, “cat”, “squirrel”, “ball”, or “fetch”. Deep dyslexic patients are unable to inhibit these other semantically related words, and they are likely to be substituted for the target word in explicit output.