1. Prof John Stein
Oxford
University
Wobbles, warbles and
fish - the brain basis of
dyslexia
D
Supported by The Dyslexia Research Trust (www.dyslexic.org.uk), R
Dyers & Colourists, Esmee Fairbairn, Garfield Weston and Wellcome
Trusts, BBC Children in Need
T

2. Reading is difficult!
‘Reading is a painful task.
It extinguishes the light from the
eyes.
It bends the back.
It crushes the viscera and the ribs.
It brings forth pain to the kidneys
and weariness to the whole body.’
13th C. Florentine monk or 20th C dyslexic!
‘Writing is not merely a copy of
speech; it is tyrannical, unnatural,
perverse, pathological and sinful’.
Jacques Derrida –founder of structuralism, 1950

3. Reading is difficult because it
requires:
1. Rapid visual identification of letters and
their order; even in experienced good readers this
process is rate limiting
2. Rapid auditory translation into the sounds
they stand for
3. Background knowledge of ‘phonology’-
how words can be split down into separate
sounds - phonemes
All these processes depend on the timing
properties of magnocellular neurones

4. Reading is Prevalence of Dyslexia
difficult!
1 in 3 of US & UK 11yr
olds leave primary school
unable to read properly
This is cruelty; they cannot
cope with high school; they
lose all self confidence
girls boys
Reading failure is the
commonest cause of
childhood misery,
depression, even suicide
Commonest disability
among College students
OR frustration, aggression,
crime; 75% of those in
gaol are illiterate.
Nevertheless, if they
survive school, dyslexics
are often highly talented –
original, artistic,
entrepreneurial boys dyslexic boys dyslexic girls girls

6. The Hurt of Dyslexia
“I am in the slow readers’ group.
My brother is in the football team
My sister is a server.
My little brother was a wise man
in the Christmas play.
I am in the slow readers group.
That is all I am in.
I hate it.”

7. Developmental Dyslexia is a
complex syndrome- not just reading
Reading and spelling significantly below that expected
from subject’s age and intelligence, despite good
health, teaching and cultural experience
Symptoms History
• Reading/IQ discrepancy • Family History (Genetic) of
• Visual sequencing problems language, literacy and psychiatric
• Auditory sequencing problems problems
-poor phonology • 20% of all boys.
• Speech impairments (lisps, • Difficult birth
spoonerisms, mispronunciations • Delayed milestones (crawling,
• Very bad spelling walking, speech)
• Left/right confusions, mixed • Developmental dyspraxia, dysphasia
handedness hyperactivity
• General sequencing problems • Autoimmune problems: asthma,
• Clumsiness & incoordination – eczema, hayfever
‘soft’ cerebellar signs • Omega 3 (fish oil) deficiency

8. 2/3rds of backward
readers complain
of visual difficulties
with reading.
Often their eyes
wobble when they
try to read. This
may be due to
weak visual
magnocellular
function

9. Reading is primarily a visual
process
Visual processing

10. Magnocellular Retinal
Ganglion cells keep eyes
still
Large magnocellular cells
(100x p- cells in area) – are
for timing visual events: fast
responses, sensitive to low
contrast, motion, flicker, for
focussing visual attention and
controlling eye movements
Most retinal ganglion cells
are parvocellular (small): for
colour, fine detail, high
contrast

11. Visual magnocellular system directs
visual attention & eye movements.

12. The visual magnocellular system
is mildly impaired in dyslexics
• Reduced visual motion sensitivity
• 30% smaller LGN • Reduced activation of cortical
magnocells post motion areas (FMRI)
• Lower sensitivity to contrast
mortem
• Lower sensitivity to flicker
• Reduced and • Lower stereoacuity
delayed evoked • Reduced visual jitter
• Weaker visual attention - slower
brain waves visual search
• Visual crowding
• Unstable eye control • Mini left neglect - clock drawing
• Prolonged line motion illusion
• Reduced Ternus effect

13. Abnormal magnocells in dyslexic brain

14. Delayed Brain Potentials Evoked
by Moving Visual Stimulus

16. Vergence control
• The eyes have to converge
for near vision when reading
• Control of vergence eye
movements is dominated by
the visual magno system
• The vergence eye movement
control system is the most
vulnerable to drugs and
disease
• Dyslexics have very
unstable vergence control

17. Magnocellular processing sharpens:
into

18. Weak magnocellular system causes
unstable vision - oscillopsia
“The letters go all blurry”
“The letters move over each other, so I
can’t tell which is which” “The words are all
“The letters seem to float all over the
page” tangled up inside
“The letters move in and out of the page” my head. I’m
“The letters split and go double” confused. I get
“The c moved over the r, so it looked like
another c” tangled up in
“The p joined up with the c” writing the words,
“d’s and b’s sort of get the wrong way and I stop.”
round”
“The page goes all glary and hurts my
eyes”
“I keep on losing my place”

19. Interventions that improve
m- function and eye control
often improve reading
In some children with poor
eye control temporary
blanking of left eye improves
vergence control and reading
by 2 months/m (proved by randomised
controlled trials –RCT)
In older children exercises
can stabilise binocular
fixation and greatly improve
reading (proved by RCT)
Yellow or blue coloured filters
can often rebalance visual M-
input and greatly improve
reading (av. 2 ms/m -proved by RCTs)

20. Yellow Filters
• Although they do not contribute to
colour vision, retinal magnocellular
ganglion cells are most responsive
to yellow light
• So in some children yellow filters
can increase magnocellular and
visual motion sensitivity and
binocular control, hence improve
reading

22. Yellow filters can improve reading
Increase in literacy in 3 months
8
7
6
5
months
yellow
4
placebo
3
2
1
0
reading spelling

24. Blue makes the letters keep still!

25. Blue filters improved reading even more
Increase in literacy
14
12
10
months
8 blue
6 placebo
4
2
0
reading spelling

26. Blue entrains
hypothalamus clock headache
to day length
hypothalamus
Blue
light
Diurnal
rhythms
M-system
B - Dull Shifting Y - Highly Labile

27. Blue can
also
improve
headaches
Dyslexic
artist
portrays
her
migraine!

28. The colour choice of 297 reading disabled 9 year olds
yellow 26%
no colour preference
49% 1
2
3
blue 25%

29. Elucidating the role of the visual system in reading has enabled us to develop
techniques for helping most of the dyslexics we see
Reading age increase in 3 months
8
**
7 **
6
RA incr. (months)
5 * *
4
*
3
nil grey normal, yellow occlusion search blue omega 3s
2 reading
recovery
1 (phonology)
0

30. Magno deficit causes many dyslexics to confuse the
visual order of letters!

31. D
The auditory/phonological R
pathway T

32. Hearing differences
between letter sounds
requires sensitivity to
changes in frequency
and intensity
2nd and 3rd formants
ascend in frequency
for ‘b’; but descend for
‘d’.
Test sensitivity to
warbles

33. Meltham Primary School

34. Developmental Dyslexics are less sensitive to
changes in sound frequency and intensity –
warbles.
• Slow frequency changes in speech are tracked in real time by
large magnocells in the auditory system
2 Hz FM 40 Hz FM
3 0.16
Detection Threshold (Mod. Index)
2 Hz FM 40 Hz FM
p<0.001 p=0.027
0.12
2
0.08
500 Hz
1 0.04
pure
0.00 tone
0
Dyslexics (N=21) Controls (N=23) Dyslexics (N=21) Controls (N=23)
Detection Threshold (Mod. Index)
240 Hz FM
0.012 p=0.360, N.S. 240 Hz FM
0.008
0.004
0.000
Dyslexics (N=21) Controls (N=23)
Witton, Talcott, Hansen, Richardson, Griffiths, Rees, Stein & Green, 1998

35. Many dyslexics
also have
phonological
problems,
partly caused
by auditory
magnocellular
impairments

36. Auditory and visual magnocellular sensitivity determines
over half of the differences in children’s reading ability
The most important determinant of overall reading ability is
magnocellular neuronal sensitivity. Encouraging because
this can be improved

37. What causes this
general
magnocellular
impairment?
Genetic
Nutrition

38. Genetic linkage
• Are particular genes associated with poor
reading?
• Analyse the DNA of father, mother and
their dyslexic and normally reading children
• 400 Oxford families
• EU consortium; 1000 families, 2000 cases,
2000 controls, 50,000 markers per case

39. C6 KIAA gene
controls
neuronal
migration during
early brain
development in
utero.
Downregulation
may explain
mismigration
and impaired
development of
magnocellular
neurones

40. Autoimmune conditions in dyslexics and
30
controls
allergies
25
20
% affected
15
Dyslexic
eczema Control
10
asthma
5 uveitis
migraine
0
1 2 3 4 5

41. Cod Liver Oil Queue, 1950

42. ‘Most Britons were
better fed in 1943 than in
today’ Dr Hugh Sinclair,
Magdalen College, Oxford
• Aged 28, he persuaded
the WWII government to
provide free cod liver oil and
orange juice to all pregnant
mothers and young children
• 20% of the brain consists
of omega-3s, mainly DHA
• Essential for flexible
membranes – rapid neural
responses
• Modern diet very deficient
in fish oil omega–3s

43. Visual Dyslexia & Diet

44. Durham study - Omega 3 EPA supplements helped
dyspraxic children to improve their concentration and
their reading (RCT – Richardson & Montgomery)
Increase in Reading age in 3 months
10
9
8
7
RA increase
6
n-3
5
placebo
4
3
2
1
0
n-3 placebo

45. Fish oils, vitamins & mineral supplements reduced
offences in Young Offenders by 1/3rd
Ratio of Rate of Disciplinary Incidents Supplementation/Baseline
1.4
Active
1.2
Placebo
1
0.8
0.6
0.4
Error bars at 2SE
to indicate the 95%
confidence interval
0.2
0
Before Supplementation During Supplementation

46. So fish is indeed good for the
brain!
• By increasing
membrane flexibility,
improves magnocellular
responses
• Help focussing
attention, hence
improves reading
• Improves self-control,
hence reduces violence
• Improves memory
(Alzheimer’s)
• Prevents accumulation
of Alzheimer’s protein

47. Conclusions
•Fundamental auditory, visual & motor temporal
sequencing requirements of speech and reading are
mediated by magnocellular neuronal systems in the
brain
•These are impaired in dyslexia
•Treatments that improve m- function improve
reading
•Weak magnocellular function may result from:
Genetic vulnerability
Fatty acid (fish oil) deficiency
•These weaknesses can be remedied: auditory and
phonological training, eye exercises, coloured filters,
fish oil supplements
BUT… dyslexia carries talent as well

49. Wobbles, warbles
and fish - the
magnocellular
brain basis of
dyslexia
John Stein
Support D
The Dyslexia Research Trust R
(www.dyslexic.org.uk) T