PSYC4080D Learning Disabilities 1

PSYC4080D Learning Disabilities 2 A word on definitions… A “learning disability” (LD) is an administrative term Each school board has it’s own definition. In Ontario, there are 14 definitions of LDs boards, provincial an federal government (Helps, 2000) DSM-IV has 3 subtypes: 1.Reading Disorder 2.Mathematics Disorder 3.Disorder of Written Expression

PSYC4080D Learning Disabilities 3 Prevalence Different definitions makes it is hard to determine prevalence Estimates range from 2 to 20% of the population (Smith, 1994). Literature defines Specific Language Impairments (SLI) separately from dyslexia 1/2 of children in special needs classes have a diagnosed LD.

PSYC4080D Learning Disabilities 4 Case Study When I’m in class, there’s not enough time to copy from the board. I lose my place. I try hard but get lost. It takes me a long time to check nearly every word to find my place. It’s really easy to get frustrated. When I’m in class, there’s not enough time to copy from the board. I lose my place. I try hard but get lost. It takes me a long time to check nearly every word to find my place. It’s really easy to get frustrated. When my teacher checks my work I have lots of mistakes. I don't like having to stay in to finish copying from the board. I can't read the joined up writing, I don't always know what letter to write. I never know what I have written. I can't see the words on the whiteboard. They can move around and sometimes I see two words the same. When my teacher checks my work I have lots of mistakes. I don't like having to stay in to finish copying from the board. I can't read the joined up writing, I don't always know what letter to write. I never know what I have written. I can't see the words on the whiteboard. They can move around and sometimes I see two words the same.

PSYC4080D Learning Disabilities 5 Case Study I didn’t want to ask for help because I didn’t want people to know I have a disability. I didn’t want people to think I was stupid. I didn’t want to ask for help because I didn’t want people to know I have a disability. I didn’t want people to think I was stupid. It was also hard when I was able to get a notetaker for my classes. There were a few people who didn’t believe I had a problem and who said that I was lazy. It was also hard when I was able to get a notetaker for my classes. There were a few people who didn’t believe I had a problem and who said that I was lazy.

PSYC4080D Learning Disabilities 6 DSM-IV Criteria 1.Reading Disorder 2.Mathematics Disorder 3.Disorder of Written Expression A.Achievement in any of these areas, as measured by individually administered standardized tests, is substantially below that expected given the person’s chronological age, measured intelligence, and age-appropriate education.

PSYC4080D Learning Disabilities 7 DSM-IV Criteria B. The disturbance in Criterion A significantly interferes with academic achievement or activities of daily living that require the ability. C. If a sensory deficit is present, the difficulties are in excess of those usually associated with it.

PSYC4080D Learning Disabilities 8 Pure Alexia Pure word blindness Pure word blindness Affects vision, cannot read their own writingAffects vision, cannot read their own writing Able to write (no agraphia or other writing disability) Able to write (no agraphia or other writing disability) Able to recognize words that are spelled aloud to them (auditory) Able to recognize words that are spelled aloud to them (auditory) No visual agnosia (ability to recognize objects) No visual agnosia (ability to recognize objects)

PSYC4080D Learning Disabilities 9 Alexia: Pathology Occipital lobe lesions Occipital lobe lesions Preventing visual information from reaching (left) extrastriate cortex Preventing visual information from reaching (left) extrastriate cortex Lesions to posterior corpus callosum Lesions to posterior corpus callosum

PSYC4080D Learning Disabilities 10 How do we read? At least two different processes: 1.Phonetic (sound-based) reading unfamiliar words unfamiliar words requires recognition of individual symbols requires recognition of individual symbols sounds associated with letters and numbers sounds associated with letters and numbers 2. Whole-word reading familiar word, we recognize it by its shape familiar word, we recognize it by its shape context: “reading is predicting” context: “reading is predicting”

PSYC4080D Learning Disabilities 11 Model of the reading process VisualPerceptionCognition Whole Word Recognition Phonetic Word Recognition

PSYC4080D Learning Disabilities 12 Model of the reading process VisualPerceptionCognition Whole Word Recognition word feature extraction word recognition, phonemic expression Phonetic Word Recognition

PSYC4080D Learning Disabilities 13 Model of the reading process VisualPerceptionCognition Whole Word Recognition word feature extraction word recognition, phonemic expression Phonetic Word Recognition letter feature extraction phoneme recognition, expression

PSYC4080D Learning Disabilities 14 Whole word reading Evidence comes from the study of dyslexias: Acquired: brain damage in those who already know how to read Acquired: brain damage in those who already know how to read Result of some trauma (tumour, stroke)Result of some trauma (tumour, stroke) Developmental: difficulties in children learning to read Developmental: difficulties in children learning to read Congenital illness or early childhood traumaCongenital illness or early childhood trauma

PSYC4080D Learning Disabilities 15 Dyslexias 1. Surface Dyslexia Deficit in whole word reading Deficit in whole word reading Errors related to visual appearance of words Errors related to visual appearance of words Semantic understanding is normal Semantic understanding is normal They rely predominantly on phonetic reading for understanding They rely predominantly on phonetic reading for understanding Cannot read irregular words Cannot read irregular words

PSYC4080D Learning Disabilities 16 Dyslexias 2. Phonological Dyslexia Are able to read familiar words using whole word method Are able to read familiar words using whole word method Cannot linking letters to phonemes Cannot linking letters to phonemes Trouble reading or learning unfamiliar words or nonwords Trouble reading or learning unfamiliar words or nonwords

PSYC4080D Learning Disabilities 17 Dyslexias 3. Word-form or spelling dyslexia Cannot recognize whole words or sound them out phonetically Cannot recognize whole words or sound them out phonetically Can recognize individual letters and can read words if naming the letters one at a time Can recognize individual letters and can read words if naming the letters one at a time Very slow readers Very slow readers Normal auditory recognition Normal auditory recognition Words spelt aloudWords spelt aloud Word memory intactWord memory intact

PSYC4080D Learning Disabilities 18 Dyslexias 4. Direct dyslexia Phonemic and whole word reading intact Phonemic and whole word reading intact Able to read aloudAble to read aloud Semantic deficit: Cannot link words to meaning Semantic deficit: Cannot link words to meaning Cannot understand words they’re sayingCannot understand words they’re saying Cannot match words with corresponding pictures Cannot match words with corresponding pictures

PSYC4080D Learning Disabilities 19 Dyslexias 5. Comprehension without reading Unable to read phonetically Unable to read phonetically Some comprehension of words they cannot read Some comprehension of words they cannot read However, can match words they can’t read with pictures However, can match words they can’t read with pictures

PSYC4080D Learning Disabilities 20 Dysgraphia: Writing Disorders Two types: 1.Motor control  directing movements to form letters and words 2. Various cognitive-based disorders  writing numbers but not letters  writing uppercase but not lowercase letters  Writing consonants but not vowels  writing single letters but not words  They have normal motor control

PSYC4080D Learning Disabilities 21 How do we write? There are four possible ways: There are four possible ways: 1. Phonetic: Sound them out before writing may do this with long, unfamiliar words may do this with long, unfamiliar words 2. Imagery: Transcribing an image of what a word looks like visual image of word is kept in mind during writing visual image of word is kept in mind during writing 3. Serial memory: Memorization of letter sequences memory of sequences of letters in a word memory of sequences of letters in a word 4. Motor memory: often repeated written words (signature)

PSYC4080D Learning Disabilities 22 Dysgraphias 1. Phonetic (phonological dysgraphia) Unable to sound out words and write them phonetically Unable to sound out words and write them phonetically They cannot write unfamiliar words or pronounceable nonwords They cannot write unfamiliar words or pronounceable nonwords Can visually image familiar words, then write them (visual, not phonetic strategy) Can visually image familiar words, then write them (visual, not phonetic strategy) Caused by damage to the (left) superior temporal lobe Caused by damage to the (left) superior temporal lobe

PSYC4080D Learning Disabilities 23 Dysgraphias 2. Image-Based (orthographic dyslexia) Disorder of visually based writing Disorder of visually based writing Can only sound out familiar words Can only sound out familiar words Can write pronounceable nonsense words Can write pronounceable nonsense words Have difficulty spelling irregular words Have difficulty spelling irregular words

PSYC4080D Learning Disabilities 24 Dysgraphias 3. Serial Memory memorizing sequences of letters that spell particular words (I.e. spelling bee) memorizing sequences of letters that spell particular words (I.e. spelling bee) Cippolitti and Warrington (1996): patient with a Left Hemisphere stroke Cippolitti and Warrington (1996): patient with a Left Hemisphere stroke Disrupted ability to spell wordsDisrupted ability to spell words Impaired ability to recognize a word that examiners would spell aloudImpaired ability to recognize a word that examiners would spell aloud

PSYC4080D Learning Disabilities 25 Dysgraphias 4. Pure Motor Memory (direct dysgraphia) Can Write words that are dictated to them even thought they cannot understand these words Can Write words that are dictated to them even thought they cannot understand these words

PSYC4080D Learning Disabilities 26 Neuropathology 1.Superior temporal lobe (Galaburda and colleagues, )  perisylvian cortex (surrounding syvian fissure)  abnormalities in part of Wernicke’s area called the planum temporale associated with developmental dyslexia  left planum temporale is usually larger in normal controls  in dyslexics they are both equal size  not all people with dyslexia show this anomaly

PSYC4080D Learning Disabilities 27

PSYC4080D Learning Disabilities 28 Neuropathology 2. Visual and auditory pathway abnormalities Magnocellular layer of LGN (thalamus) may be damaged (Galaburda & Livingstone, 1993) Magnocellular layer of LGN (thalamus) may be damaged (Galaburda & Livingstone, 1993) Motion and spatial locationMotion and spatial location MGN damage in thalamus can cause difficulties in hearing MGN damage in thalamus can cause difficulties in hearing Dyslexics often have difficulties with perception of letters and of movements in space Dyslexics often have difficulties with perception of letters and of movements in space Particularly with developmental dyslexiaParticularly with developmental dyslexia

PSYC4080D Learning Disabilities 29 What and Where Pathways Albright & Stoner, 2002

PSYC4080D Learning Disabilities 30 Neuropathology More on visual pathway deficits…  Transposition of letters is commom: moving around, merging, and becoming blurry  Maybe related to eye movements, since fixation is often unsteady  Motion sensitive areas of V5 in the extrastriate cortex (posterior temporal lobe) are not activated in persons with LDs to moving stimuli

PSYC4080D Learning Disabilities 31 Etiology 1.Focal neuroanatomical abnormalities Cell migration in perisylvian structures Cell migration in perisylvian structures Ectopias: abnormal positioningEctopias: abnormal positioning Focal microgyri: small lesionsFocal microgyri: small lesions Cytoarchitecture in thalamic nuclei Cytoarchitecture in thalamic nuclei Disorganized, smaller cell bodies in magnocellular LGN and MGN neuronsDisorganized, smaller cell bodies in magnocellular LGN and MGN neurons Genetic correlate of these abnormalities found in mice Genetic correlate of these abnormalities found in mice

PSYC4080D Learning Disabilities 32 Etiology 2. Primary phonological deficits cause secondary sensory and motor deficits  Perisylvian anomalies are primary  Cortical lesions produce secondary thalamic abnormalities  Affecting relay neurons to vision, audition, motor centres

PSYC4080D Learning Disabilities 33 Other Information LD is a lifelong disorder. LD is a lifelong disorder. Many people who have LDs may either compensate for their difficulties, or avoid situations where their weaknesses are likely to show. Many people who have LDs may either compensate for their difficulties, or avoid situations where their weaknesses are likely to show. More and more universities have special services for those with LDs. More and more universities have special services for those with LDs. Not so in the workplace – problems may go unnoticed. Not so in the workplace – problems may go unnoticed.