The Annual Newsletter of the International Reading Association's Phonics Special Interest Group
Changes in Brain Function in Children with Dyslexia after Training
by
Elise Temple
Department of Human Development
Cornell University
Introduction
Developmental Dyslexia
Developmental dyslexia is defined simply as difficulty reading despite
the intelligence, motivation, and education necessary for successful reading
[1].
Its prevalence is still an active area of research but has been estimated
at any where between 5 and 17% of the population, therefore representing
a very large national and international concern [1]. Studies have shown
that the reading deficits of children with developmental dyslexia have
persisted into adolescence and even adulthood. The disorder cannot be
explained as a simple developmental lag [1]. A number of different methods
have suggested a neurobiological basis for the disorder, but the fundamental
cause (or causes) remains unknown and is an active area of research on
many fronts [2, 3]. It is important to note that there are many risk factors
for difficulties in reading that are not biological. For example, home
literacy environment and socio-economic status can predict reading ability
[4]. These factors can and should be addressed in educational and social
policy. The biological basis for dyslexia is considered when those risk
factors have been accounted for and a reading deficit remains.
Importance
of Phonological Awareness
A developing consensus among many researchers is that developmental dyslexia
is characterized by difficulties in phonological processing, specifically
phonological awareness which is the ability to identify and manipulate
the sound structure of words [1, 4]. Individuals with dyslexia have impaired
phonological skills, including the ability to distinguish rhyming sounds,
count the syllables of words, and sound out novel or “pseudo-words”
(e.g., “stroat” or “traim”). Phonological awareness
skills are thought to be a required foundation for both normal-reading
and dyslexic children to benefit from phonics instruction.
Auditory Processing
In addition to a deficit in phonological processing, individuals with
dyslexia have been shown, by some researchers, to have a more fundamental
deficit in auditory processing, specifically auditory processing of rapid
auditory sounds that are entering the nervous system in the 10’s
of milliseconds [5, 6]. This deficit in processing rapid auditory stimuli
is thought to impact language and subsequently reading because some of
the sounds in language, or phonemes, differ only in frequency changes
that occur in the first 40-50 ms of the sound. The idea behind the rapid
auditory processing hypothesis of developmental dyslexia is that without
this ability to detect rapid auditory signals the child is unable to distinguish
certain phonemes and develops an inadequate or “fuzzy” understanding
of the phonology or sounds of his/her language. This inadequate understanding
of the sounds of the words in the language is especially problematic when
the child learns to read and is required to map letters onto their appropriate
sounds.
Functional Brain Imaging
With the advent of new technology that allows us to visualize brain function
in adults and children, researchers have begun to explore brain function
and possible dysfunction in adults, and more recently children with developmental
dyslexia. There are a few methods available to measure brain function
in children. The type used in the current study is called functional magnetic
resonance imaging or fMRI. FMRI is a variant of traditional MRI, which
is used for visualization of any soft tissue inside the body (including
the structure of the brain and spinal cord).
While MRI allows us to see the structure of the brain, fMRI allows us
to see the function of the brain. The technique is based on the fact that
when you think, see, or imagine there is an increase in brain function
(neurons firing) in specific and localized parts of the brain. Increased
brain function causes an increase in blood flow. The increase in blood
flow, brings about an increase in oxygen, that can be measured by fMRI.
More oxygen occurs naturally in areas of the brain that are working harder.
The technique is entirely noninvasive (it requires no injections or imaging
contrasts) and can be used safely in children
.
Brain Function in Dyslexia
Studies of brain function in dyslexia using this and other techniques
have shown people with dyslexia seem to have a neural disruption in phonological
processing as well as the behavioral deficit described earlier. A number
of studies, using different methods and subject groups, have found that
when people with dyslexia are asked to do some tasks that require phonological
processing they have less brain function (as compared to normal reading
controls) in a specific brain area. This decreased activity is localized
to a part of the brain on the left side called the temporo-parietal cortex,
a region of the brain located a little behind and above the ear [2]. (See
figure.) This decrease in brain function has been shown in adults with
dyslexia and even non-English speaking adults with dyslexia.
More recently, children with dyslexia have also been shown to have decreased
activity in this brain region, suggesting that the disruption may be fundamental
to the disorder and not an effect of years of compensation. What has not
been known is the extent to which this decrease in brain function could
be changed with training or education.
The Current Study
The current study [7] was designed to test whether this decrease in activity
could be changed in children with dyslexia. We hypothesized that we might
be able to see changes in brain function in children with dyslexia after
remediation and we expected two types of changes. One type of change we
might see would be a normalizing of the activity in the left temporo-parietal
region discussed above. We might see increases in activity in this region,
bringing the dyslexic brain closer to the normal-reading brain. We also
expected that we might see increased activity in other regions of the
brain, perhaps reflecting a compensatory effect of the training on brain
function.
Methods
Training program
The training program used in the study was Fast ForWord Language (www.scilearn.com),
which focuses on auditory processing and oral language through an intensive
and adaptive computer program [8, 9]. One unique feature of the program
is a focus on training children to discriminate rapid auditory signals.
It also emphasizes other aspects of oral language, including auditory
attention, memory, phonological processing, and listening comprehension.
The training lasted approximately 8 weeks and included 100 minutes a day,
5 days a week.
Experimental Design
The study included children 8-12 years old with dyslexia (n=20) who underwent
fMRI scans before and after training. In addition, 12 normal-reading children
underwent two fMRI scans about 8 weeks apart to control for any practice
effects, normal development, and scan–rescan effects. The children
performed a phonological processing task while undergoing fMRI. The task
was a simple rhyming task. Each child was shown two letters and asked
to push a button if the names of the two letters rhymed with each other
(e.g., “T” and “D” rhyme, whereas “G” and
“K” do not). This was compared to a matching task where the
child simply indicated if the two letters were the same letter (e.g.,
“P” and “P”). The rhyming task was designed to require
phonological analysis of the letters’ names, but was simple enough
for a poor or beginning reader to perform.
By comparing the brain function during the rhyming task with the brain function during the matching task, we could focus on the brain function specifically associated with phonological analysis rather than orthographic processing of letters or other task demands (like pushing a button, being in an MRI machine, etc.).
Results
Reading and Language Ability
We found that the children with dyslexia, as a group, demonstrated improved
performance on reading measures after the training program. Their performance
on the Woodcock Johnson Reading Master subtests improved significantly
and, as a group, was now in the normal range. (WJR-MT scores: Word Identification:
pre training = 78.2, post training = 86.0, p<0.0005; Word attack: pre
training = 85.5, post training 93.7, p
< 0.0001; Passage Comprehension:
pre-training = 83.3, post training = 88.9, p < 0.001). Similar improvements
were seen in oral language measures (CELF-3: receptive: pre training =
92.5, post training = 101.3, p < 0.001; expressive: pre training =
95.0, post training = 102.2, p < 0.006).
Brain Function
In our analysis of brain function, we found a number of brain areas that
showed changes, after training, in the children with dyslexia. In line
with our expectations, we did see an increase in the left temporo-parietal
cortexes in the children with dyslexia after training. This region was
near the region which had been shown to be under-active in these children
compared to normal reading children. This increase in brain function had
a normalizing effect, in that it brought the brain function of children
with dyslexia closer to that of normal-reading children. This normalization
was not complete however; the children with dyslexia did not reach normal
levels of activity in this region.
In addition, we saw increased activity in a number of regions not normally
involved in phonological processing. These regions included parts of the
right side of the brain which are mirror images of the normal left-sided
language processing areas. These increases may reflect more of a compensatory
effect of the training, where the right side of the brain gets involved
to help the damaged left side. Right-sided help for language in people
who have left-sided damage has been reported in studies of stroke recovery
where increased right-sided activity was associated with improved language
after stroke.
In summary, we found a partial amelioration of the disrupted brain function
seen in children with dyslexia after training; they showed partial normalization
of activity in the left temporo-parietal cortex. In addition, we saw compensatory
effects of training, especially in increased activity in the right side
of the brain.
Conclusion
This study was the first to use fMRI to explore possible changes in brain
function after behavioral training in children with dyslexia. The training
used was Fast ForWord Language, a training program that focuses on oral
language and auditory processing. After training, the children with dyslexia
improved in reading and language ability. In addition, after training,
the children with dyslexia showed changes in brain function. These changes
in brain function were both “normalizing” and “compensating.”
Normalization of brain function in children with dyslexia included increased
brain function in the left temporo-parietal cortex, above and behind the
left ear. After training there was increased activity in this region,
which had been shown to be under-active in children and adults with dyslexia.
“Compensating” effects of the training included increased activity
in regions of the brain that are were not normally active during such
tasks. These increases were seen especially in the right side of the brain,
in mirror images to the traditional left-sided language areas, perhaps
reflecting a tendency by the right side of the brain to compensate for
the left side’s inability to function fully. This study shows that
the brain dysfunction seen in dyslexia can be affected by behavioral training.
The implications of this study are numerous. First, this study shows that
it is possible to study the brain effects of training in human children.
Previous research on brain plasticity had been largely limited to animal
research. This study opens up the possibility for further research that
explores different inter-ventions and educational strategies.
Second, this study shows that a specific remediation program, Fast ForWord
Language, resulted in changes in brain function in children with dyslexia
while improving their reading ability. Finally this study shows that previously
reported brain dysfunction in dyslexia can be at least partially ameliorated.
These results should help give hope to the individuals struggling with
dyslexia and their families and teachers. Dyslexia is not simply a matter
of a child not “trying hard enough.” This brain research has
shows us that the biological aspects of dyslexia can be changed and at
least partially normalized.
Please see the actual scientific article for more detail
on this study: Temple, E., et al., Neural deficits in children with dyslexia
ameliorated by behavioral remediation: Evidence from fMRI. Proc Natl Acad
Sci U S A, 2003. 100(5): p. 2860-2865.
References
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