of evidence. More recently, however, two much more satisfactory pieces of evidence have emerged.
Patterson, Vargha-Khadem and Polkey (1987) report a study of a person who first exhibited signs of a
left-hemisphere abnormality at 13 and had a left hemispherectomy at age 15. Given her age, it is likely
that language development in the two hemispheres would have reached maturity. Prior to the onset of her
left-hemisphere symptoms she was a normal reader for her age. After her hemispherectomy she displayed
all the major symptoms of deep dyslexia:
Semantic errors (arm -> “finger”, pigeon -> “cockatoo”)
Visual errors (bush -> “brush”, frost -> “forest”)
Morphological errors (duck -> ducks”, smoke -> “smoking”)
Very poor reading of function words
Nonword reading impossible.
Michel, Henaff and Intrilligator (1996) report the case of a 23-year-old man who as a result of
neurosurgery was left with a lesion of the posterior half of the corpus callosum. He was able to resume his
college studies in accountancy after recovering from surgery. Michel et al studied his reading by briefly
presenting words to the left hemisphere (i.e. in the right visual hemifield) or the right hemisphere (left
visual hemifield), with these results:
Right visual hemifield: Words were read rapidly, and with 100% accuracy. Judgement of whether
two words rhymed or not was 94% accurate.
Left visual hemifield:
Numerous semantic errors such as bijou -> “perle”, poulet -> “garlic”.
Concrete words read better than abstract words.
Function words poorly read.
Nonword reading virtually impossible.
At chance on judging whether two words rhymed.
These two studies would seem to provide conclusive evidence for the right-hemisphere interpretation of
deep dyslexia.
Treatment
In deep dyslexia, the brain damage is extensive, the reading impairment is severe, and the patient is
aphasic as well as dyslexic. Nevertheless, the condition responds to appropriate and intensive treatment;
this has been demonstrated by de Partz (1986).
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