Pure alexia results from cerebral lesions in circumscribed brain regions and therefore belongs to the group of acquired reading disorders, alexia, as opposed to developmental dyslexia found in children who have difficulties in learning to read.
Pure alexia exhibits some unexpected residual abilities despite the inability to read words. For instance, one patient had preserved calculation capabilities such as deciding which number was greater, and whether a number was odd or even with greater than chance probability. The study showed that the patient was also able to calculate simple arithmetic tasks such as addition, subtraction, and division, but not multiplication, even though the patient could not read the numbers. For example, the patient would be presented with "8 – 6", and he or she would read it as "five minus four", but still come up with the correct answer "two" with greater than chance accuracy. Pure alexia patients also seem to retain some residual semantic processing. They are able to perform better than chance when forced to make a lexical decision or make a semantic-categorisation decision. These subjects also performed better with nouns than functors, better with words that had high rather than low imageability, and performed poorly with suffixes. However, this may be due to right hemisphere input or residual left hemisphere input.
In patients, a common symptom is letter-by-letter reading or LBL. This action is a compensatory strategy which these patients use in order to come up with a semblance of reading. It is essentially looking at the consonants and vowels of the word and sounding them out as they sound. However, this method does not always work, especially for words like 'phone' where the ph sounds like an f, but if sounded out, does not sound like an f. Also, by reading words in the fashion, the rate at which patients read words is much slower compared to people who do not have this disability. Petersen et al. proved that the issue of reading time had more to do with the length of the words than reading ability. The team had 4 patients with right hemisphere damage and 4 patients with left hemisphere damage in the temporo-occipital lobes as well as 26 controls were shown one word at a time on a screen. They were exposed to 20 words of 3 and 5 letters, 12 words of 7 letters. The subjects were asked to read the words as quickly and as accurately as possible. The patients with left hemisphere lesions consistently read the longer words slower than the controls despite the difficulty of the word. It is thought that as the word gets longer, the letters on the outsides of the word go into peripheral vision, making the patient shift their attention thus making the patient take longer to read.
Though there have been ample attempts to rehabilitate patients with pure alexia, few have proven to be effective on a large scale. Most rehabilitation practices have been specialized to a single patient or small patient group. At the simplest level, patients seeking rehabilitation are asked to practice reading words aloud repeatedly. This is meant to stimulate the damaged system of the brain. This is known as multiple oral re-reading (MOR) treatment. This is a text-based approach that is implemented in order to prevent patients from LBL reading. MOR works by reading aloud the same text repeatedly until certain criteria are reached. The most important criteria for a pure alexic patient is reading at an improved rate. The treatment aims to shift patients away from the LBL reading strategy by strengthening links between visual input and the associated orthographic representations. This repetition supports the idea of using top-down processing initially minimize the effects peripheral processing which were demonstrated in the study above. From here, the goal is to increase bottom-up processing. This will hopefully aid in word recognition and promote interactive processing of all available information to support reading. 'The supported reading stimulation from MOR has a rehabilitative effect so that reading rate and accuracy are better for untrained text, and word-form recognition improves as evidenced by a reduced word-length effect.' These tactics have seen quite good success.
Another tactic that has been employed is the use of cross modal therapy. In this therapy, patients are asked to trace the words in which they are trying to read aloud. There has been success using cross modal therapy such as kinaesthetic or motor-cross cuing therapy, but tends to be a more feasible approach for those on the slower reading end of the spectrum.
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