Dyslexia Assessment & Diagnosis
What is the normal development of reading skills?
Developmental studies suggest that two distinct procedures are implicated in the development of the reading system. When learning to read, a child initially builds up a sight vocabulary of familiar words where mappings are formed between visual patterns of written words and their pronunciations. Words with irregular sound-to-spelling correspondences can only be read via this strategy, known as the lexical procedure. However, to be able to decode the many new words encountered when learning to read, the child must develop an alternative reading strategy, based on the component letters of the word and the corresponding letter sounds. This phonological strategy operates at a subword level, first by segmenting any unfamiliar written word into its individual letters or letter segments (graphemes) and then by blending together the corresponding speech sounds (phonemes).
What is Dyslexia?
Many children experience difficulties in acquiring the phonological strategy of reading. These difficulties are thought to arise from a deficit in the awareness of the phonological structure of words, which prevent learning of letter-to-sound correspondences needed for phonological reading. Recent studies of brain function have highlighted abnormalities in the neural mechanisms underlying phonological treatment in individuals with phonological dyslexia. Adults and children with dyslexia show decreased activity in the left temporal cortex, as well as significant overactivation of the left inferior frontal region during phonological processing. Such abnormal neural responses have been observed in a number of studies, using different methodologies, such as PET and fMRI techniques, and across multiple tasks (e.g., rhyming, nonword vs word reading, and explicit and implicit reading). These findings strongly suggest an implication of both temporal and frontal lobes in the phonological processing of reading.
Assessment of Dsylexia
To assess for dyslexia at the SCDC we conduct an IQ test as well tests of reading, phonological awareness, and possibly visual processing. The IQ test will show what level of reading would be expected from the child. This way calculations can be performed to look at whether the child is significantly performing below their level of potential. The IQ test also assessed working memory and processing speed skills which can be fundamental to acquisition of reading skills. We then perform tests of reading accuracy, speed and comprehension. We also assess phonological awareness, that is, how well a child can break down words into sounds as well as blend sounds into words. This also looks at phonological memory as well as rapid naming and retrieval. If a child is having problems memorising sight words, this could also indicate issues with visual memory or visual processing, and this may be assessed by higher level visual processing tests (eg. visual discrimination, visual closure etc...). We may recommend that if other cognitive issues are noted, such as poor attention skills or more widespread memory problems, that the child has a more comprehensive neuropsychological assessment, or combines a dyslexia assessment with an ADHD assessment. At the Sydney Cognitive Development Centre all testing is tailored to individual needs.