Transcript Document

Dislessie acquisite
Deficit di lettura dopo una lesione
cerebrale
Dislessie acquisite: approcci
neurologici
Alessia parieto-occipitale (o alessia
con agrafia) - associata a sintomi
afasici
Alessia occipitale (o alessia senza
agrafia)
Alessia frontale (o alessia letterale)
Jules Dejerine (1849-1917)
J. Déjerine, Sur un cas de cécité verbale avec agraphie suivi d’autopsie, in :
<Mémoires de la Société de Biologie>, vol. 3, 1891, pp. 197–201.
J. Déjerine, Contribution à l’étude anatomo-pathologique et clinique des
différentes variétés de cécité verbale, in: <Mémoires de la Société de
Biologie>, vol. 4, 1892, pp. 61– 90.
J. Déjerine, J. Tinel, Un cas d’aphasie de Broca, in: <Revue Neurologique>,
vol. 16, 1908, pp. 691-694.
Dislessie acquisite: approccio
cognitivo
Analisi degli errori di lettura
Errori semantici (via - strada)
Errori visivi (banale - banane)
Sostituzione di parole funzione (questo- quello)
Errori morfologici (entrano - entrando)
Errori di lessicalizzazione: viornale - giornale

A syndrome is a collection of symptoms that tend to occur together. Cognitive neuropsychologists don't use the concept of
syndrome in their theorizing because, if the kinds of modular models of cognition favoured in cognitive neuropsychology are
even roughly correct, the number of different possible syndromes of impairment in any domain of cognition is gigantic. So the
probability of ever seeing two patients with the same syndrome (i.e. exactly the same pattern of preserved and impaired
components of a particular cognitive processing system) is essentially zero.

However, syndrome labels do have their uses. Firstly, they are convenient shorthand terms that can convey to other people a
quick though only approximate idea of what impairments a patient has. Secondly, it has turned out that in any domain of
cognition that is unexplored from a cognitive-neuropsychological point of view, a good way to begin such exploration is to try to
identify some basic broadly-defined syndromes, even if this way of thinking will subsequently be abandoned as impairments in
this domain become better understood

That's what happened with respect to reading, the first domain to be studied in detail by cognitive neuropsychologists. The first
paper on the cognitive neuropsychology of reading was published in Neuropsychologia in 1966 by Marshall and Newcombe; it
was on the particular syndrome of acquired dyslexia known as deep dyslexia. They followed this up with a paper on three
syndromes of acquired dyslexia (deep dyslexia, surface dyslexia, and visual dyslexia); this was published in the Journal of
Psycholinguistic Research in 1973. A fourth syndrome of acquired dyslexia was first described in 1979, by Beauvois and
Derouesne in the Journal of Neurology, Neurosurgery and Psychiatry. And in 1982 in the Quarterly Journal of Experimental
Psychology, Patterson and Kay discussed a fifth syndrome which they called letter-by-letter reading; it is also known as pure
alexia, and had in fact first been described about a century ago by the French neurologist Dejerine, though he and subsequent
authors had not approached this acquired dyslexia in a cognitive-neuropsychological way (that is, they had not attempted to
relate it to models of normal reading).
Syndromes of acquired dyslexia

A third use for the syndrome concept is that it is a good device for teaching material about acquired dyslexia; a good
way of organizing basic knowledge of the area. So what I will do here first is to describe the general features of these
five syndromes of acquired dyslexia so as to make it clear what they are like and how they differ from eachother.

Having provided an overview of the basic characteristics of each of these acquired dyslexias, I will then go on to
discuss how each relates to the model of language processing we are using; it will be at that point that we will move
away from the concept of syndrome and adopt the real cognitive-neuropsychological approach. That approach is, of
course, to treat each patient as a unique case, but to try to relate every patient to the model, by asking: can we see
how all the patient's symptoms could arise from damage to specific components of the model, with all the other
components being intact.

Ellis and Young's "Human Cognitive Neuropsychology" has an excellent basic chapter on acquired dyslexia which you
should read at this point.
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* Deep Dyslexia.
* Surface Dyslexia.
* Phonological Dyslexia.
* Pure alexia (Letter-by-letter reading).
* Visual Dyslexia.
* Neglect Dyslexia.
Explaining the different patterns of
acquired dyslexia in relation to a
model of normal reading.


Here is a model of the processes
skilled readers use to read single
words and nonwords aloud and to
understand the meanings of single
words.
If any of the boxes or arrows in this
diagram are not functioning normally,
then reading will be abnormal in some
way. So we could try to understand
different patterns of acquired dyslexia
by trying to work out which boxes
and/or arrows have been affected by
brain damage in each of these cases.
This works very well for some kinds of
acquired dyslexia, but less well for
others.
Deep dyslexia

Introduction

The first systematic study of deep dyslexia was by Marshall and Newcombe (1966),
although the condition had been sporadically mentioned in the neuropsychological
literature at least since 1931.Marshall and Newcombe (1973) and Shallice and
Warrington (1975) also published early systematic studies. An entire book on deep
dyslexia was published in 1980 (Coltheart, Patterson and Marshall, 1980), and much
work on deep dyslexia has appeared since then.
The symptoms of deep dyslexia.

All patients so far reported with deep dyslexia have had extensive left-hemisphere damage sufficient to
produce aphasia (normally Broca's aphasia) and normally also a left hemiparesis. This acquired dyslexia is
identified by the occurrence of semantic errors in reading aloud. Single words are presented, without
context and without time pressure, for reading aloud; even in this simple situation the deep dyslexic will
often produce a reading response that is related in meaning to the stimulus word but may be quite different
from it in spelling and pronunciation, such as reading the word canary as "parrot". Although the semantic
error in reading aloud is the key symptom of deep dyslexia, many other reading symptoms are also seen
in this form of acquired dyslexia (for review see Coltheart, 1980a, 1987a).Deep dyslexics generally show
all of the following symptoms in reading-aloud tasks:

* Semantic errors, such as "tartan" read as "kilt" or"anchor" read as "boat".
* Visual errors: a visual error in reading is when the response shares many letters with the stimulus,
such as quarrel read as "squirrel" or angel read as "angle".
* Morphological errors: a morphological error in reading is when a prefixed or suffixed word is read with
the root of the word correct but the prefix or suffix wrong, such as running read as"runner" or unreal read
as "real".
* Concreteness effect: concrete (highly-imageable) words such as tulip or green are much more likely to
be successfully read than abstract (difficult-to-image) words such as idea or usual.
* Function words such as and, the or or are very poorly read.
* Nonwords such as vib or ap cannot be read aloud at all.
* Spelling/writing may be impossible; if it is at all possible, then it usually shows the spelling equivalent
of the above 6 symptoms.
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Deep dyslexia as left-hemisphere reading.

Cognitive neuropsychologists seek to understand cases of acquired dyslexia by investigating how one could
selectively damage a component or some components of a model of reading so that the model would exhibit the
same symptoms as the patient.

For deep dyslexia,this was attempted by Morton and Patterson (1980, 1987) as follows: First, since nonword
reading is completely abolished in deep dyslexia, the letter-to-sound rules system must have been abolished.

Second, since word reading is much less than 100% accurate, the direct connection from the Orthographic Input
Lexicon to the Phonological Output Lexicon must be impaired. Take function words, for example. The deep
dyslexic can recognize these as words (since visual lexical decision performance with such words can be very
good) and can produce them (since the usual error response to a function word is another function word). Hence
the problem in reading them must be a disconnection between recognition and production.

Third, since reading is worse for abstract words than for concrete words, there must also be an impairment of the
Semantic System that is worse for abstract than for concrete words.

Fourth, the Semantic System must be impaired in such a way that semantic errors occur e.g. that "parrot" and
"canary" are not successfully distinguished in the semantic system.

Fifth, since sometimes the deep dyslexic will correctly understand a printed word but make a semantic error in
reading it aloud, the connection between the Semantic System and the Phonological Output Lexicon must be
damaged in such a way that a correct semantic representation yields an incorrect (semantically related) reading
response.

Sixthly, there must be damage to whatever the syntactic system is that is used for processing prefixes and
suffixes, to account for morphological errors in reading affixed words.
Deep dyslexia as left-hemisphere reading

The argument is that if the model has these 6 kinds of damage its reading will exhibit all the
symptoms of deep dyslexia. A problem with this argument is that if these are really six different
ways in which the reading system can be damaged, then one would expect to see patients with
forms of acquired dyslexia that represent subsets from this set of six forms of damage. For
example, there would be no reason why someone should not just have the first five
impairments: that would mean we should see cases of acquired dyslexia where there are
semantic errors but no morphological errors; similarly.when all but the third form of damage is
present, we would see semantic errors but no advantage for concrete words. Patterns like these
have never been observed. For that, and other, reasons an alternative theoretical account of
deep dyslexia was proposed by Coltheart(1980,1987) and Saffran, Bogyo, Schwartz and Marin
(1980, 1987). They proposed that deep dyslexia was unique amongst the acquired dyslexias in
that these patients are not reading with a damaged version of the normal reading system which
is in the left hemisphere. Instead,they cannot use the left hemisphere at all for reading. Their
reading is carried out by a separate reading system, located in the right hemisphere.
Deep dyslexia as right-hemisphere reading.

Coltheart (1980b, 1987b) and Saffran, Bogyo, Schwartz and Marin(1980, 1987) supported their
arguments that reading in deep dyslexia was carried out by a right-hemisphere reading system by
pointing out a number of resemblances between deep dyslexic reading and what was then known
about language in the right hemisphere: there was evidence, from split-brain patients, of poor syntax
in the right hemisphere (which would impair processing of function words and affixes), and there was
evidence from experiments with lateralized presentation of words to intact subjects of a concrete
word superiority with right-hemisphere (left visual field)presentation. There was also Gott's report of a
young girl who had learned to read but then had a left-hemispherectomy, after which semantic errors
appeared in her reading aloud of single words.

However, there was much that was inadequate about this evidence.For example, the well-studied
split-brain patients all had bilateral brain damage from birth, so one cannot safely generalize from
their hemispheres to the hemispheres of people who had intact brains in adulthood prior to the
damage that caused deep dyslexia. Similarly,Gott's patient exhibited an encephalopathy at an age
earlier than that at which language lateralization would have been complete, so she too is not a
completely satisfactory source of evidence. More recently, however, two much more satisfactory
pieces of evidence have emerged.
Deep dyslexia as right-hemisphere reading
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Patterson, Vargha-Khadem and Polkey (1987) report a study of a person who first exhibited signs of a left-hemisphere
abnormality at 13 and had a left hemispherectomy at age 15. Given her age, it is likely that language development in
the two hemispheres would have reached maturity. Prior to the onset of her left-hemisphere symptoms she was a
normal reader for her age. After her hemispherectomy she displayed all the major symptoms of deep dyslexia:
* Semantic errors (arm -> "finger", pigeon -> "cockatoo")
* Visual errors (bush -> "brush", frost -> "forest")
* Morphological errors (duck -> ducks", smoke -> "smoking")
* Very poor reading of function words
* Nonword reading impossible.

Michel, Henaff and Intrilligator (1996) report the case of a 23-year-old man who as a result of neurosurgery was left
with a lesion of the posterior half of the corpus callosum. He was able to resume his college studies in accountancy
after recovering from surgery. Michel et al studied his reading by briefly presenting words to the left hemisphere (i.e. in
the right visual hemifield) or the right hemisphere (left visual hemifield), with these results:


* Right visual hemifield: Words were read rapidly, and with 100% accuracy. Judgement of whether two words
rhymed or not was 94% accurate.
* Left visual hemifield:
o Numerous semantic errors such as bijou -> "perle", poulet -> "garlic".
o Concrete words read better than abstract words.
o Function words poorly read.
o Nonword reading virtually impossible.
o At chance on judging whether two words rhymed.

These two studies would seem to provide conclusive evidence for the right-hemisphere interpretation of deep dyslexia.

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Treatment
In deep dyslexia, the brain damage is extensive, the reading impairment is
severe, and the patient is aphasic as well as dyslexic. Nevertheless, the
condition responds to appropriate and intensive treatment; this has been
demonstrated by de Partz (1986).
References

Coltheart, M. (1980a, 1987a). Deep dyslexia: A review of the syndrome. In Deep Dyslexia. op cit.

Coltheart, M. (1980b, 1987b) Deep dyslexia: A right-hemisphere hypothesis. In Deep Dyslexia. op.cit.

Coltheart, M., Patterson, K. and Marshall, J.C. (Eds): Deep Dyslexia. London: Routledge and Kegan Paul, 1980 (Second
Edition 1987).

De Partz, M.P. (1986) Re-education of a deep dyslexic patient: Rationale of the method and results. Cognitive
Neuropsychology, 3,149-177.

Marshall, J.C. and Newcombe, F. (1966) Syntactic and semantic error sin paralexia. Neuropsychologia, 4, 169-176.

Marshall, J.C. and Newcombe, F (1973) Patterns of paralexia: A psycholinguistic approach. Journal of Psycholinguistic
Research,2,175-199.

Michel, F., Henaff, M.A. and Intriligator, J. (1996) Two different readers in the same brain after a posterior callosal
lesion.NeuroReport,7, 786-788.

Morton, J. and Patterson, K. (1980, 1987) In Deep Dyslexia. Op cit.

Patterson, K., Vargha-Khadem, F. and Polkey, C. (1987) Reading with one hemisphere. Brain, 112, 39-63.

Saffran, E., Bogyo, L.C. Schwartz, M. F. and Marin, O.S.M. (1980,1987). Does deep dyslexia reflect right-hemisphere
reading? In Deep Dyslexia, Op. cit.

Shallice, T. and Warrington, E.K. (1975) Word recognition in a phonemic dyslexic patient. Quarterly Journal of Experimental
Psychology, 27, 187-199.

Weekes, B., Coltheart, M. and Gordon, E. Deep dyslexia and right-hemisphere reading - A regional cerebral blood flow
study. Aphasiology, 1997, 11, 1139-1158.
Introduction

Surface dyslexia was first described by Marshall and Newcombe (1973), and
subsequently by Shallice, Warrington and McCarthy (1983). An entire book on
surface dyslexia was published in 1985 (Patterson, Marshall and Coltheart,
1985), and a number of other studies of surface dyslexia have appeared since
then. Surface dyslexia also occurs as a form of developmental dyslexia i.e. as
a specific pattern of difficulty in learning to read, in children without any sign of
neurological abnormality.
The symptoms of surface dyslexia

About three-quarters of the words of English are regular words. This term
refers to words which obey the standard spelling-to-sound rules of English:
words like new, jetty or howl. The remaining 25% or so of words are irregular
words, also referred to as exception words; such words contain at least one
violation of English spelling-to-sound words. Examples are sew, pretty and
bowl. The defining symptoms of surface dyslexia are:

* Exception words are less often read correctly than regular words matched
to the exception words on word frequency, number of letters, etc.;
* When an exception word is misread, the error is generally a regularization
error i.e. the pronunciation given is the one specified by the rules. For
example, pretty is read as if it rhymed with "jetty", and bowl is read as if it
rhymed with "howl".

Parole
regolari
•1
•2
•3
•4
•5
•6
•7
•8
•9
•10
•11
•12
•13
•14
•15
•16
•17
•18
•19
•20
•21
•22
•23
•24
•25
•26
•27
•28
•29
•30
take
free
market
effort
plant
middle
check
drop
luck
navy
chicken
context
weddind
smog
tail
victor
weasel
mist
infest
curb
nerve
pump
peril
radish
brandy
stench
ditty
marsh
flannel
cord
frequenza
611
260
155
145
125
118
88
59
47
37
37
35
32
1
24
23
1
14
1
13
12
11
8
8
7
1
1
4
4
6
irregolari
come
sure
island
answer
blood
pretty
break
lose
soul
iron
colonel
routine
ceiling
quay
bowl
regime
meringue
shoe
indict
pint
gauge
tomb
choir
debris
cough
brooch
beret
yacht
bouquet
wolf
frequenza
630
264
167
152
121
107
88
58
47
43
37
35
31
0
23
23
0
14
0
13
12
11
8
8
7
0
0
4
4
6
Non-Parole
•1
•2
•3
•4
•5
•6
•7
•8
•9
•10
•11
•12
•13
•14
•15
gop
teg
nad
lif
sut
stet
mulp
prin
nint
gren
thim
chut
sith
phot
giph
•16
•17
•18
•19
•20
•21
•22
•23
•24
•25
•26
•27
•28
•29
•30
hoil
toud
gead
doil
roin
gurdet
torlep
tadlen
latsar
polmex
tashet
sothep
miphic
lishon
dethix
ail - ale
air - err
aisle - isle - I'll
all - awl
ate - eight
bail - bale
bait - bate
ball - bawl
balm - bomb
band - banned
bard - barred
baron - barren
base - bass
bask - Basque
be - bee
beach - beech
bear - bare
beat - beet
beat - beet
beer - bier
bird - burred
birr - burr
blew - blue
bloc - block
board - bored
bold - bowled
boor - bore
boos - booze
born - bourne
bough - bow
brake - break
bread - bred
broach - brooch
broom - brume
grate - great
groan - grown
guessed - guest
hail - hale
hair - hare
hay - hey
heal - heel - he'll
hear - here
heard - herd
hi - high
him - hymn
hoarse - horse
hole - whole
hour - our
I - eye
browse - brows
brut - brute
but - butt
buy - bye
Cain - cane
capital - capitol
cast - caste
cede - seed
ceiling - sealing
cell - sell
cellar - seller
chard - charred
sew - so
shear - sheer
shoe - shoo
sighs - size
sight - site - cite
sign - sine
slow - sloe
cheap - cheep
check - Czech
chews - choose
chilli - chilly
coarse - course
collard - collared
cored - cord
creak - creek
cue - queue
curd - Kurd
dam - damn
dane - deign
days - daze
dear - deer
die - dye
doe - dough
done - dun
Ernest - earnest
ewe - yew - you
faint - feint
fair - fare
feat - feet
file - phial
find - fined
flea-flee
flew - flue - flu
flour - flower
foul - fowl
four - for - fore
frays - phrase
frees-freeze-frieze
gait - gate
gilt - guilt
gored - gourd
in - inn
knap - nap
knave - nave
knead - need
knew - new
knot - not
know - no
knows - nose
leak - leek
led - lead
liar - lyre
lie - lye
light - lite
links - lynx
loan - lone
maid-made
mail - male
main - mane
maize - maze
mall - maul
manner - manor
mews - muse
might - mite
moor - more
morning - mourning
mote - moat
muscle - mussel
nay - neigh
night - knight
none - nun
one - won
or - ore
pail - pale
pain - pane
Homophones: spelling fun
Is it "deer" or "dear"?
Speaking of which or witch?
A dog has a tail. A story's a tale.
The postman brings the mail., A boy's a male.
A knight wears shining armour, at night we sleep (and
speaking of wears, wares are also the goods sold in
shops and … Where are you going?)
I have some chocolate. I make the sum of three plus
three.
You say "bye" to your friends after school. You buy a
loaf of bread. We go by the pharmacy on our way
downtown.
I carry a pail of water. Mary is as pale as a ghost.
The police go to the site of a crime. Teachers often
cite the words
of Shakespeare.
We're in sight of the Statue of
Liberty.
The theoretical interpretation of surface dyslexia

Because the nonlexical route reads by applying letter-sound rules, it will misread
words that don't obey those rules; indeed, it will produce regularization errors with
such words. Therefore, according to the model, correct reading aloud of exception
words depends upon the lexical reading route. Hence damage to the lexical route
will result in surface dyslexia: nonwords (and regular words) will still be read
correctly, but exception words will often result in regularization errors.

Since the lexical route has a number of different components, there are a
number of different ways in which it can be damaged so as to produce surface
dyslexia, and so any two patients with surface dyslexia may have quite
different patterns of damage in the lexical route. Two examples of such
damage are (a) damage to entries in the Orthographic Input Lexicon and (b)
damage to entries in the Phonological Output Lexicon. If the word pretty has
been lost from the Orthographic Input Lexicon, it won't be recognized lexically,
so will be read nonlexically and so will be regularized. If it has been lost from
the Phonological Output Lexicon, it will be recognized when it is seen, but its
pronunciation won't be retrieved from the Phonological Output Lexicon, so will
have to be generated nonlexically - so again a regularization error will occur.

In some of the early studies of surface
dyslexia, the disorder was not pure, in
the sense that reading by the nonlexical
route was not completely intact. Doubts
were therefore raised about the
interpretation of surface dyslexia in
terms of a model with separate lexical
and nonlexical pathways. However, pure
cases were eventually discovered: MP
(Bub, Cancelliere and Kertesz, 1985)
and KT (McCarthy and Warrington,
1986). Both of these patients were poor
at reading exception words, especially
when these were of low frequency, and
virtually all of their errors were
regularization errors; critically, the
accuracy and even the speed of their
reading of nonwords was within normal
limits. So they represent two pure cases.

Both of these patients had semantic
impairments. KT's was a progressive
semantic deterioration. In other patients with
"semantic dementia" (progressive loss of
semantic knowledge due to progressive
atrophy of temporal lobes), surface dyslexia
is also often seen (which is why the NART
can be inappropriate as a test for estimating
premorbid intelligence). In these cases, the
surface dyslexia is presumed to be due to
an impairment of entries in, or access to, the
Phonological Output Lexicon that
accompanies the semantic impairment (so,
as suggested in discussions in PSYP811, a
lexical decision task such as Baddeley's
"Spot the Word" test, with low frequency
words, might be better than the NART for
estimating premorbid intelligence).
Developmental surface dyslexia

Holmes (1973), Coltheart, Byng, Masterson, Prior and Riddoch (1983) and Temple
and Marshall(1983) have described cases of developmental surface dyslexia, and
Castles and Coltheart (1994) have shown that this form of developmental dyslexia is
not uncommon. These are children who have no trouble with the phonic side of
reading and quickly learn to sound out words by letter-sound rules; their particular
problem in learning to read is in developing a big enough sight vocabulary. They
recognize by sight many fewer words than other children their age who are making
normal progress in learning to read. Hence many exception words which the normal
children can read aloud correctly will be regularized by the developmental surface
dyslexic.
Surface dyslexia

Surface dyslexia: if brain damage
has deleted words from the visual
word recognition system, the
reading aloud will have to rely on
letter-to-sound rules. In that case,
regular words will still be read
correctly but irregular words won't.
Word
visual analysis
parser
word detectors
(input logogens)
semantic system
Phonological word representations
(output logogens)
response buffer
“Word”
translator
retranslate
blender
pint
p
int
analisi
1. deaf
2. deaf
d
d
/pint/
/p/ /int/
decodifica
eaf
ea f
assemblaggio
“nessuna traduzione”
/d/ /i/ /f/
riparsing
/dif/
“nessuna parola” --> retranslate (lexical check)
3. deaf
d
ea
f
/d/ /e/ /f/
/def/
Treatment

Both acquired and developmental surface dyslexia have been successfully treated, in
small-scale single-case studies, by a mnemonic technique aimed at restoring or
introducing whole words to the Orthographic Input Lexicon (see Byng and Coltheart,
(1986), Coltheart and Byng (1989) and Weekes and Coltheart (1996) for work on the
treatment of acquired surface dyslexia).
References

Byng, S., and Coltheart, M. (1986) Aphasia therapy research: methodological requirements and illustrative results.
In Nilsson, I.G., and Hjelmquist, E. (Eds.), Communication and Handicap: Aspects of Psychological Compensation
and Technical Aids. Amsterdam: North-Holland Publishing.

Castles, A. and Coltheart, M. Varieties of developmental dyslexia. Cognition, 1993, 47, 149-180.

Coltheart, M. Varieties of developmental dyslexia. Cognition, 1987, 27, 97-101.

Coltheart, M. and Byng, S. (1989) A treatment for surface dyslexia. In Seron, X. (Ed.). Cognitive Approaches in
Neuropsychological Rehabilitation. London: Lawrence Erlbaum Associates Ltd.

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