Reading, Alexia, and Dyslexia



Reading, Alexia, and Dyslexia

I. Learning to read (for an alphabetic script like English)

phonological awareness – awareness of how sound maps onto graphemes

very important for beginning readers (phonic method works a lot better than whole-word method of teaching reading)

During normal development, awareness seems to begin with small units (individual letter-sound mappings, e.g., 1 letter = 1 phoneme), and then progresses to larger units (e.g., syllables)

Phoneme-letter awareness seems to best predict subsequent reading skill.

SO: Right from the start, sound and writing go hand in hand.

II. “Dual route” model of normal reading

Graphemes

direct phonological

“visual” recoding

route

Word recognition/

lexical access

Definitions:

grapheme-to-phoneme (spelling-to-sound) “rules”

regular words – those that correspond to the most common patterns

(e.g., steam, hint)

irregular words – those that do not correspond to the most common patterns

(e.g., steak, pint, yacht, aisle)

For normal reading, there seems to be a “race” between the two routes, which both occur; the speediest “wins”

III. Alexia (in the U.K., acquired dyslexia)

A. Syndromes

1. “peripheral” alexias (affect visual processing system)

a. spelling alexia

takes forever to read a word; each letter is processed individually, one at a time

2.”central” alexias (specifically affect reading system)

a. surface alexia (reading by sound)

selective impairment in ability to read irregular (exception) words (e.g., yacht, pint)

pint ( spoken o that it rhymes with “hint”

steak ( steek

yacht ( yached

But, comprehension of these words is normal. mostly

b. phonological alexia (reading by sight)

selective impairment in ability to read pronounceable nonword (pseudowords)

can’t read aloud “sleeb”, although they can read “sleep”

c. deep dyslexia

semantic reading errors (paralexias)

Written word … Read aloud as …

daughter sister

rose flower

etc

IV. Dyslexia (in the U.K., developmental dyslexia)

very common (depending on how you define it, 5-20% of the population)

Relationship between dyslexia and alexia is not clear. (I think they are very distinct.)

Possible causes:

1. phonological processing deficit

a. lack of phonological awareness

b. poor ability to segment speech stream into phonemic units

2. visual processing deficit

a. problem processing closely spaced, highly detailed visual objects (like letters)

Treatments:

1. Try to increase phonological awareness.

2. Try to improve ability to segment speech stream into phonemes (e.g., Fast ForWord)

Language as a social behavior

Language is learned and used in a social context.

Language itself is inherently a social activity.

But we tend to forget this . . .

I. Birdsong and social interaction (Beecher & Hurt, 2004)

Social interaction is important for song learning!

- some songbirds will not learn from a taped song but require live birds as their song tutors

- songs are learned more quickly and accurately with a live bird tutor than with taped song

- the “critical period” for song learning is longer when birds learn from live birds rather than from taped song

- which variants of song a bird learns is often determined by social factors (e.g., the adult birds’ relative standing in the social hierarchy, their relative closeness to the learner, etc)

II. In humans, language learning might be intricately linked to children’s general tendency to imitate adults

A. Meltzoff: Babies can imitate adult behavior from a startlingly early age

B. The ability to imitate might be linked to a “mirror neuron” system that humans and other primates have

- located in Broca’s area and in the homologous area in monkeys

- are activated both when the monkey or person performs some motor movement, AND when the monkey or person observes another monkey or person performing that motor act

- mirror neurons therefore seem to match observed events to similar internally generated actions, thereby forming a lilnk between the observer and the actor (and hence facilitate imitative behavior)

C. The ability to learn a language might crucially depend on imitation, and mirror neurons might play a role in that (Rizzolatti & Arbib, 1998)

- mirror neurons are now thought to play a role in higher cognitive processes, not just motor movement (e.g., langage, or being able to imitate and learn form others’ actions, decode their intentions, or feel their pain)

III. Normal social interactions are essential for normal language development

A. Social deprivation (e.g., Genie)

B. Autism

a disorder of social interaction, with very abnormal communicative function

New evidence suggests that autistics might have dysfunctional mirror neurons!

Ramachandran (2005): dysfunctional mirror neurons might account for autistic’s language dysfunction

- “mu frequency” of EEG seems to reflect mirror neuron function; in normal people, mu activity is high in response to their own movement or other peoples’ movements

- mu frequency is very low in autistic children

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download