READING DISABILITY- ETIOLOGICAL PERSPECTIVE

PRESENTED BY- SOFIYA NAZIR (A0423412001)

B.A+M.A- CLINICAL PSYCHOLOGY- SEMESTER 5

MODERATED BY- BABITA PRUSTY

CONTENTSDEFINITION OF READING DISABILITY

READING DISABILITY AND LEARNING DISABILITY

EPIDEMIOLOGY

ROUTE TO READING

COGNITIVE BASIS OF READING DISABILITY

THEORIES OF READING DISABILITY

ETIOLOGY OF READING DISABILITY

REFERENCES

DEFINITIONDyslexia is a specific learning disability that is

neurobiological in origin. It is characterized by difficulties

with accurate and/or fluent word recognition and by poor

spelling and decoding abilities. These difficulties typically

result from a deficit in the phonological component of

language that is often unexpected in relation to other

cognitive abilities and the provision of effective classroom

instruction. Secondary consequences may include problems

in reading comprehension and reduced reading experience that

can impede growth of vocabulary and background knowledge

(Lyon 2003).

READING DISABILITY AND LEARNING

DISORDER“The Individuals With Disabilities Education Act (IDEA)

provides that “specific learning disability” means “a disorder

in 1 or more of the basic psychological processes involved

in understanding or in using language, spoken or written,

which disorder manifest itself in the imperfect ability to

listen, think, speak, read, write, spell, or do mathematical

calculations”. such term “includes such

conditions as perceptual disabilities, brain injury, minimal

brain dysfunction, dyslexia, and developmental aphasia.” such

term does not include “a learning problem that is primarily the

result of visual, hearing, or motor disabilities, of mental

retardation, of emotional disturbance, or of environmental,

cultural, or economic disadvantage.”

EPIDEMIOLOGYA recent epidemiological study indicates the prevalence rate of

dyslexia to be around 9.87 per cent among Indian school children.

5- 17% prevalence rate of dyslexia in school aged children of united

states of America

3-6% in united kingdom

In Chinese and Japanese people prevalence rate is as low as 1%

1% prevalence rate in elementary school population in Egypt

EPIDEMIOLOGY

0.98

0.11

0.45

0.10.1

indian america ukchinese egypt

ROUTE TO READING DUAL ROUTE TO READING

The indirect route (phonological)translating the letters into sounds and knowing the pronunciation of words from the combination

of sounds.

The direct route

(orthographic)

Looking at word and

automatically knowing

what it says

COGNITIVE BASIS OF READING DISABILITY DEFICITS OF PHONOLOGICAL SKILLS

Inability to

break down spoken

words into

phonemes

Phonemic awareness

IMPAIRED DECODING SKILLS

graphemes phonemes

THEORIES OF READING DISABILITY

THE CORE PHONOLOGICAL DEFICIT THEORY- This

theory is proposed by Snowling and Vellutino( 2000). This

theory posits that poor phonemic awareness and poor mastery

of the alphabetic principle are the key underlying deficits seen

in most dyslexic individuals.

DOUBLE DEFICIT THEORY- This theory was developed

and presented in 1993 by bowers and wolf. It is a culmination

of two deficits, it explains that students with phonological

awareness deficits and RAN ( Random Autonomic Naming)

deficits are poorer readers than those students with only one

deficit. Bowers and Wolf (1993) discuss four subtypes of

readers:

Good non word decoders and good fluency in regular word

reading

Poor non word decoders while demonstrating good fluency in

regular word reading ( single deficit of phonological

awareness)

Good non word decoders while demonstrating poor fluency in

regular reading words ( single deficit with RAN)

poor non word decoders and poor fluency in regular reading

words ( double deficits)

ETIOLOGY OF READING DISABILITY

GENETIC FACTORS- Dyslexia runs in families and

dyslexia in a parent is one of the strongest predictors of dyslexia

in the child. Across studies, about 40% of parents who have

offspring with dyslexia have dyslexia themselves. The

association is greater for fathers than for mothers, with

aggregated figures of 46% and 33% respectively (grigorenko

2001).

1. TWIN STUDIES- One study found that the concordance

rate for pairs of monozygotic twins was around 70%,

whereas the corresponding concordance rate for reading

disability in same-sex dizygotic twins was 48%, a highly

significant difference.( Colorado twin project)

2. CHROMOSOMES- Four genes that affect reading are

•DCD2, KIAA0319 (both on chromosome 6p)

•DYX1C1 (on chromosome 15)

•ROBO1 (on chromosome 3)

FUNCTIONAL BRAIN IMAGING

Through the use of technologies like PET, fMRI and MEG,

several research groups elicited the activation pattern of brain

areas during phonological processing tasks in dyslexics. The

results were-

BRAIN STUDIES- Post mortem studies have reported two

significant changes in the brains of dyslexics-

1. A region of the superior temporal gyrus known as the planum

temporale has been shown to lack asymmetry in such

individuals.

2. Changes in the left-hemisphere perisylvian region and parts

of the thalamus in individuals with dyslexia, specifically the

presence of abnormally large cells, ectopias (‘brain warts’)

and dysplasia. These cellular abnormalities in the brain are

thought to result from failure of neural migration.

REFERENCES