Most of the problems reported in clinical pediatrics, neurology,
neuropsychology and speech therapy are related to learning disabilities
and/or developmental language disorders.
Learning disabilities are believed to be closely related to a past
history of developmental language disorders. Learning disabilities
are concerned with abnormal development of verbal and/or written
expression and reception. Therefore, the early detection of these
disabilities prevents later educational and social consequences
The aim of the present study is to provide health professionals,
especially pediatricians, with adequate tools, so as to diagnose
and prevent oral and written language disorders. To start with,
we focus on the normal language developmental process, the neurobiological
and environmental causes of these disorders, showing their implication
on several developmental stages. Finally, we present a brief therapeutic
Language is an example of higher cortical function, and its development
is based on a genetically defined anatomic and functional structure,
and on verbal stimuli provided by the environment ().
Language is a means of communication, that is, it is a social instrument
of interaction used for communication. Thus, language should be
regarded as a dynamic force or process instead of a product. It
may be defined as a conventional system of arbitrary symbols, combined
systematically to store and exchange information ().
Before children can speak, they use their eyes, facial expression
and gestures to communicate with others. They can also distinguish
sounds of speech. Learning the linguistic code is dependent upon
the acquired knowledge about objects, actions, places, properties,
etc. It results from the complex interaction between innate biological
abilities and environmental stimuli, advancing according to neuropsychomotor
Although the level of efficiency with which language is acquired,
is not well established, it is common knowledge that children from
different cultures follow the same global path of language development.
While still in utero, they learn the sounds of their native
language, and in their first months of life, they distinguish these
sounds from those of other languages ().
Two distinct phases of language development exist: the prelinguistic
phase, with vocalization of sounds but no words, which persists
up to the 11-12th month of life; and the linguistic phase, when
infants start to utter single but meaningful words. Later on, language
expression becomes complex. This is a continuous process that occurs
in an orderly and sequential fashion, with considerable overlapping
of different developmental stages ()
Table 1 -
Language acquisition encompasses the development of four interdependent
systems: pragmatic (communicative use of language in a social context),
phonological (perception and production of sounds to form words),
semantic (processing of meaning), and grammatical (use of syntactic
and morphological rules to combine words into meaningful sentences).
The phonological and grammatical systems constitute the language
form. The pragmatic system describes how language should be adapted
to specific social situations in order to convey emotions and reinforce
Intention to communicate may be expressed nonverbally through facial
expression, signs, and also by children's ability to answer questions,
wait for their turn, make questions and discuss their point of view.
This communicative competence shows that knowing to adapt language
to a given situation and knowing the rules for social communication
is as important as semantic and grammatical awareness ().
Biological aspects of language
The language process is quite complex, and consists of a neuronal
network distributed through different regions of the brain. In contact
with environmental sounds, speech is comprised of multiple sounds
that occur simultaneously at different frequencies and with increased
variability. The ear must tune into this complex auditory signal,
decipher it and translate it into electric impulses, which are carried
by nerve cells to the auditory region of the cerebral cortex (temporal
lobe). There, impulses are reprocessed and transmitted to language
areas, where the acoustic signal is probably stored for a certain
period of time ().
Wernicke's area, in the temporal lobe, recognizes the pattern of
auditory signals and interprets them until concepts or thoughts
are obtained, activating a distinct group of neurons for different
signals. Neurons are also activated in the lower portion of the
temporal lobe, forming an image of what was heard, whereas neurons
in the parietal lobe store related concepts. According to this model,
the neuronal network forms a complex processing unit ().
The inverse process is necessary for verbalization of thoughts.
Initially, there is an inner representation of the topic, which
is organized into Broca's area, in the lower portion of the frontal
lobe and converted into patterns of neuronal activation necessary
for the production of speech. Areas responsible for motor control
and memory are also involved in language development ().
The brain is a dynamic organ that is always adapting to new information;
consequently, the areas associated with language in adult individuals
might not be the same in children. Some brain zones might be used
only during language development ().
The left hemisphere is believed to be language dominant in approximately
90% of the population, however, the right hemisphere is responsible
for processing information, especially with respect to pragmatic
Etiology of oral and written language disorders
Speech involves articulation, resonance, voice, fluency/rhythm and
prosody. Language difficulties are among the most frequent developmental
disabilities, affecting 3-15% of children. They may be classified
into delay, dissociation, and deviance ()
Table 2 -
Classification of language alterations
The etiology of language and learning disorders varies considerably,
and may include organic, intellectual/cognitive, and emotional factors
(relational familial structure), and these factors are most times
correlated. Learning disabilities may co-occur with other conditions
(mental retardation, emotional disorders, sensory/motor disorders)
or may be exacerbated by external factors, such as cultural differences,
poor or inadequate education ()
Table 3 -
Etiology of written and verbal language disturbances
Language and epilepsy
The effects of epilepsy, seizures and electroencephalographic discharges
on language have been widely discussed in several studies. The most
frequent disorders observed in epileptic patients are: developmental
dysphasia associated with epilepsy; acute aphasia (transient dysfunction
of the cognitive function), and acquired epileptiform aphasia (Landau-Kleffner
Acquired epileptiform aphasia is characterized by deterioration
of spoken language associated with seizures or abnormal epileptiform
electroencephalographic activities, being often mistaken for autistic
syndrome or hearing impairment. On top of deterioration of speech
and auditory agnosia, behavioral disorders, including autistic traits,
are also observed. Therefore, it is essential to keep an eye on
children who have language regression, evaluating them carefully
so that a differential diagnosis is established and proper treatment
is provided ().
Language and autism
Language regression is observed in Landau-Kleffner syndrome and
in autistic regression ().
Recent studies, which focus on the language of verbal children on
the autistic spectrum, emphasize aberrant features of their speech
such as unusual word choices, pronoun reversal, echolalia, incoherent
discourse, unresponsiveness to questions, aberrant prosody and lack
of drive to communicate ().
Several studies attribute the lack of speech of some individuals
to the severity of their autism, mental retardation, or to an inability
to decode auditory language ().
In autism, comprehension and pragmatics are always affected, and
findings include aberrant prosody, immediate or late echolalia and
perseveration (inappropriate repetition of a utterance). Other symptoms,
which are different from those observed in children with speech
delay, are nonverbal communication disorders, stereotyped and persistent
behaviors, restricted and/or unusual interests and impaired social
Our conclusion is that language regression in children is a severe
disorder with significant long-term comorbidities ().
Intervention in children with speech disorders
Speech and language development may be appropriate or not, depending
on chronological age. Evaluation should include cognitive and emotional
aspects of development, which may indicate or not the severity of
the disorder, as well as the necessity for specialized family guidance
and/or speech therapy ().
It is widely known that early language stimulation may prevent learning
disabilities, dyslexia, and developmental disabilities. A body of
research has demonstrated the importance of the first three years
of life to the development of the human brain ().
The basic interventions include the evaluation of language development
at all levels, family and school guidance, and therapy ().
Types of therapy include speech therapy (phonetic and phonological
deviations), voice therapy (dysphonias), oral motor therapy (eating
disorders, breathing and mobility of phonoarticulatory organs),
oral speech therapy (expressive and/or receptive language) and written
language therapy (dyslexias, dysorthographies and dysgraphias).
All stimulation activities in a child's speech therapy must be carried
out in a playful way (e.g.: games), so that children find them amusing,
and should encourage the participation of family and school, if
Stimulation through singing, talking, playing games, and reading
allow for the acquisition of skills that foster development. For
the process of communication to occur, children need to be motivated.
There should be the so-called intention to communicate (children
can obtain their objects of interest through language). This occurs
through the daily contact with people and through the stimuli that
such interaction provides. The importance of breastfeeding, foods
with adequate texture and consistency at different stages, and the
elimination of thumb sucking or pacifiers at the age of two years
should also be emphasized. All of these factors contribute to an
orofacial musculature that facilitates speech development. Family
has a crucial role in stimulating speech; it is the physician's
or therapist's decision to let the family get involved or let himself/herself
be involved by the family ().
According to constructivism, learning is construction, action and
awareness of the coordination of actions, where knowledge is built
from learners' personal experience, with a previous learning structure
or conditions, in addition to exposure to the necessary learning
Specific reading and writing development is related to a wide series
of factors, which are underpinned by the mastery of language and
capacity of symbolization, and that depend on internal and external
Reading skills are verified by child's ability related to decoding,
fluency and written comprehension ().
Normal reading occurs in two phases. First, the graphic stimulus
is visually processed. Afterwards, linguistic processing takes place,
where letters are converted to sounds through the nonlexical route,
and then words are globally read as to their meaning via the lexical
The child should find out that some letters do not correspond to
the speech sound, since "alphabetical reading associates an
auditory phonemic component with a graphic visual component, which
is known as graphophonemic correspondence" ().
It is necessary to be aware of the phonemic structure of language
(word segmentation) and of the auditory units represented by different
The process of written language acquisition, as occurs with oral
language, involves various regions of the brain, including the parieto-occipital
area. In the occipital region, the primary visual cortex is responsible
for processing graphic symbols, and parietal lobe areas are responsible
for visuospatial aspects of writing. This processed information
is recognized and decoded by Wernicke's area, which is responsible
for language comprehension, and the expression of written language
requires the activation of the primary motor cortex and Broca's
area. For all this process to occur, intra-hemispheric connections
must be intact ().
A study conducted with healthy individuals asked to read pseudo-words
revealed activation of the left inferior frontal region; parieto-temporal
region, involving the angular and supramarginal gyri, and posterior
portion of the superior temporal gyrus; and occipito-temporal regions,
involving mesial and inferior portions of the temporal and occipital
The same study was carried out with dyslexic patients, and revealed
an increase in the activation of the inferior frontal gyrus and
little activation of posterior regions.
Researchers have shown that as far as neurological mechanisms involved
in reading disabilities are concerned, hemispheric asymmetry produces
an atypical organization of the right hemisphere in dyslexic children
and adolescents ().
Dyslexics have a temporo-parieto-occipital disconnection and a disconnection
with the left frontal cortex, as well as other problems between
the temporo-parietal cortex and the cerebellum and other brain regions
Written language disorders in childhood
Learning disabilities refer to the abnormal development of reading
and written skills, and logical and mathematical thinking, and may
be associated with oral language impairment ().
When investigating oral language disorders, it is common to find
predictors of subsequent reading and writing disabilities. Likewise,
when we investigate the factors that predispose to reading and writing
disabilities, questions about language learning difficulties are
raised. It has been underscored that among oral language difficulties
in children, phonological difficulties may interfere with later
development of reading and writing skills, and not articulation
disorders, as previously thought ().
Reading and writing encompass complex cognitive skills, in addition
to the ability to reflect upon the language in phonological, syntactic,
semantic and pragmatic terms.
When children are introduced to writing they already master the
oral language, being therefore able to learn how to write. However,
we know that there are specific rules that apply to writing, which
make its learning more difficult ().
In Brazil, around 40% of children who are learning to write have
problems with their school performance. This rate drops to 20% in
industrialized countries ().
If children with learning disabilities are properly followed by
health professionals and educators, conjointly with the family,
they can succeed in school ().
As a matter of fact, there is a combination of biological and environmental
factors in written language acquisition, including motor integrity,
sensory perceptual integrity and social and emotional integrity
(actual possibilities offered by the environment in terms of quantity,
quality, and frequency of stimuli). Moreover, the mastery of language
and the ability to interpret symbols are important for the development
of reading and writing skills ().
Dyslexia is a learning disability characterized by specific reading
and writing difficulties. There are two types of dyslexia: developmental
dyslexia and acquired dyslexia ().
Developmental dyslexia refers to reading and writing disorders of
environmental origin (related to learning style). In this case,
reduced reading ability is associated with cerebral dysfunction,
denoting a specific problem with the development of reading skills,
and consequently, with learning to read ().
Some authors think genetic factors are implicated in the etiology
of developmental dyslexia. In acquired dyslexia, acquired reading
and writing skills are lost, due to brain damage.
Several factors related to the etiology of developmental dyslexia
have been under investigation, including cognitive deficits, neurological
(neuroanatomical and neurophysiological) factors, premature birth,
low birthweight, genetic and environmental factors. However, external
(environmental) factors cannot be dissociated from neurological
problems, since aspects such as poor education, emotional disorders,
and poor stimuli during childhood may cause differences in the neurological
and cognitive development, leading to severe reading disabilities
Dyslexias may be of two types: central and peripheral (Table 4).
In central dyslexias, linguistic processing is undermined, that
is, the letter-to-sound conversion is impaired. In peripheral dyslexias,
the visual perceptual system is compromised, and the understanding
of what has been read is then hindered.
Table 4 -
Classification of central and peripheral
Central dyslexias can be subdivided into phonological, surface,
and deep dyslexias, whereas peripheral dyslexias are subdivided
into attentional, neglect and pure dyslexias ().
With regard to developmental dyslexias, the most common ones are
phonological dyslexia, surface dyslexia, and semantic dyslexia.
The latter is characterized by reading aloud, with perfect letter-to-sound
conversion, but poor written comprehension ().
Several studies have provided evidence of phonological deficits
in developmental dyslexia. Nevertheless, recent studies have gathered
evidence of multiple temporal processing deficits in dyslexias.
Actually, dyslexics have visual and auditory disorders, which may
result from generalized problems with perception and selection of
Dyslexic children have auditory and visual disorders related to
spatial orientation. These findings suggest that poor utilization
of allocated space may tamper with the development of phonological
and orthographic representations that are essential to reading acquisition
A study conducted by the Institute of Cognitive Neuroscience (London)
assessed 16 dyslexic adults and 16 controls by submitting them to
a full battery of psychometric, auditory, visual and cerebellar
tests. Individual data showed that all dyslexic individuals had
phonological deficits, 10 individuals had auditory deficits, four
had motor deficits, and two of them had visual deficits. These findings
suggest that phonological deficits may occur in the absence of any
other motor or sensory disorder, and may cause significant literacy
impairment, as demonstrated by five of 16 dyslexic individuals ().
Dyslexia and attention deficit hyperactivity disorder
Most children with attention deficit hyperactivity disorder have
difficulties in school. Learning disabilities may co-occur with
A comparative study was carried out with children who had reading
disabilities but no attention deficit hyperactivity disorder, children
who only had attention deficit hyperactivity disorder, children
who had reading disabilities and attention deficit hyperactivity
disorder, and children without any disabilities. The auditory processing
in the temporal lobe of these children was investigated. The results
did not show a deficit in the auditory temporal functions in children
with reading disabilities, but they suggested that the presence
of attention deficit hyperactivity disorder is a relevant factor
for the performance of children with reading disabilities ().
Another study conducted in Holland (Department of Special Education
Vrije Universiteit Amsterdam) revealed that inhibitory deficits
in lexical dyslexics might be attributed to frontocentral dysfunctions
involved in motor inhibition, suggesting that there might be an
association between lexical dyslexia and attention deficit hyperactivity
disorder, since both groups present executive dysfunction ().
Dyslexia and low birthweight
In low birthweight infants, there exists an association between
the presence of periventricular brain injury and low performance
on reading and spelling tests ().
A U.S. study sought to establish an association between reading
disabilities and their potential risk factors in boys and girls.
The results indicated that low birthweight girls had twice the risk
of developing reading disabilities ().
Differences have been found as to the use of the cortex during reading
in low birthweight infants ().
Genetic influences in dyslexia
As some individuals have shown genetic susceptibility to reading
disabilities, several studies have been made about dyslexias taking
genetic factors into consideration. Reading has been ascribed to
specific chromosomes (6, 1, 2, 15), even though there has not been
any evidence so far of specific genes related to reading skills
Recent findings obtained from the Human Genome Project indicated
four dyslexia susceptibility genes: DYX1, DYX2, DYX3 and DYX4. These
genes are located in different positions, possibly showing the heterogeneity
of reading disorders ().
Another study, carried out by neuropsychologist Frank Wood, from
Wake Forest University, shows that other chromosomes (6, 1,2 and
15) are related to reading disabilities in some children ().
More specifically, loci on chromosomes 6 and 18 have shown replicable
effects on reading skills ().
It should be underscored that the improved knowledge about the role
of genetics in dyslexia may help diagnose and treat susceptible
children more efficiently and rapidly.
Other written language disorders - dysgraphia and dysorthographia
Written expression (assessed through copying, dictation, and spontaneous
writing) can also help detect disorders such as dysgraphia (distorted
or incorrect writing) and dysorthographia (spelling disability that
is unexpected for a given age or level of education). Dysgraphia
and dysorthographia may be associated or not with dyslexias.
The basic principles of stimulation of written language among children
are: to encourage discovery and use of logical thinking to build
words and texts and represent phonemes; to provide them with opportunities
to write and read spontaneously; to constantly explore different
writing functions (not only production of texts, but also of letters
and notes); and to show them the differences between spoken and
written language. It is essential that children become aware that
speech and writing are different forms of language expression.
As previously mentioned, problems with the perceptual reading processes
or with psycholinguistic processes (lexical, visual, phonological,
syntactic or semantic) may result in reading disabilities; in this
case, the development of a rehabilitation program should be directly
related to the assessment of children's deficits ().
In patients with surface dyslexia, a lexical strategy is used, and
in phonological dyslexics, the most appropriate strategy consists
of the letter-to-sound conversion (nonlexical) ().
The stimulation of phonological awareness in pre-readers is of paramount
importance, since various studies have demonstrated its efficiency
in reading acquisition ().
Currently, the most recommended intervention for the treatment of
children with written language disabilities is the direct approach
to reading skills, combined with activities related to phonological
processing. In the past, the practices sought to stimulate skills
considered to be prerequisites for reading acquisition, such as
visuospatial perception, psychomotor skills, etc ().
All activities that stimulate written language should be carried
out in a playful way (games), so that children find pleasure in
reading and writing. At home, parents should encourage their children
to read by reading them stories, playing rhyming games that help
with phonological awareness, playing games with letters and drawings
for them to get acquainted with writing, having them read labels
and ads; in brief, children should never be obliged to read a book;
they should be encouraged to read it in order to know what the story
is all about, instead ().
There are various causes for language disorders and learning disabilities,
although many studies indicate that neurological factors might be
implicated. Improved knowledge about the neurobiology of language
development and learning processes will certainly contribute to
a better therapeutic approach to these patients. Systematic investigation
aimed at an accurate diagnosis may guide health professionals in
choosing the best treatment for each case.