Phonological dyslexia

Last updated June 12, 2022

Phonological dyslexia is a reading disability that is a form of alexia (acquired dyslexia),^[1] resulting from brain injury, stroke, or progressive illness and that affects previously acquired reading abilities. The major distinguishing symptom of acquired phonological dyslexia is that a selective impairment of the ability to read pronounceable non-words occurs although the ability to read familiar words is not affected. It has also been found that the ability to read non-words can be improved if the non-words belong to a family of pseudohomophones.^[2]^[3]

Deep and phonological dyslexia

Individuals with phonological dyslexia have the opposite problem to surface dyslexics. These individuals are able to read using the whole word method. However, they struggle when it comes to sounding words out. Phonological dyslexics are able to read familiar words, but have difficulties when it comes to unfamiliar words or non-words that are pronounceable.^[4] Several studies have found that many phonological dyslexics have a good reading ability if the individual has developed a large vocabulary prior to having brain damage. These individuals seem to stop developing their vocabulary post-brain damage, which affects their reading capacity.^[2]

Phonological dyslexia is a reading disorder in which the patient has impaired reading of nonwords. The symptoms of phonological dyslexia are very similar to those of deep dyslexia. The major difference between these two dyslexias is that phonological dyslexics do not make semantic errors associated with deep dyslexia. Beauvois and Dérouesné (1979) studied the first case of phonological dyslexia and came up with this term.^[5] The problem people with phonological dyslexia have is that they are able to read words using the whole word method; however, they are not able to sound words out. This means that they are able to read familiar words, but have difficulties reading new words.^{[ citation needed ]}

Initially it was believed that the factor causing phonological dyslexia was lexicality; however, other factors such as imageability and concreteness also play a critical role in reading. A study done by Crisp and Lambon Ralph concluded that imageability has a significant effect on phonological dyslexia. The study found that eleven out of the twelve patients had more accuracy when reading words with high imageability.^[5] In that study, the patient who was the exception was the least severely damaged, contributing to a view of phonological dyslexia and deep dyslexia as points on a continuum rather than discrete disorders.^[5]

Physiology

Several studies have found that different levels of brain damage can lead to the occurrence of varying forms of non-word reading disorders.^[6]^[7] It has been found that during certain tasks, dyslexics had activated one of two regions of the brain: the Broca's area, which is responsible for speech, or the Wernicke's area, which is responsible for forming and understanding. Both areas were seldom active together. This study has led to the conclusion that there exist neural connection breakdowns between the language centers that may be causing dyslexia.^[8]

Hyphenation

An investigation conducted by Harley, T. A., and O'Mara, D.A. (2006) found that hyphenation significantly improved a participant's reading ability. The subject had phonological dyslexia that was due to a deficiency in graphemic parsing. The study suggested that hyphenation might be generally useful as a strategy to assist phonological dyslexics.^[9]

Case study

A study was done by Beauvois and Dérouesné on a 64-year-old man. The individual is described as right-handed, a retiree, and having formerly been an agricultural machinery representative. The individual had had surgery for a left parieto-occipital angioma. Scans showed a lesion at the left angular gyrus, the posterior part of the second temporal convolution, the inferior longitudinal fasciculus, the geniculostriate fibres and tapetum. The patient was also found to have neurological defects such as right inferior quadrantanopia, mild memory deficit, mild calculation impairment, minimal constructional apraxia, and astereognosia. It was found that the patient did not have motor or sensory defects. He had been obliged to retire as the phonological dyslexia disrupted his ability to work. He had previously enjoyed reading, but was now unable to read his own or other pieces of writing. The diagnosis was confirmed with the Alouette reading test, which concluded that the patient had a reading disability. He was found to have the reading ability of a 6-year-old child, which is considered to be the lowest reading level. The level of reading was not determined from the speed, rather from the fact that the patient was not able to read more than 62 of the stimuli presented in three minutes, while 40% of the represented stimuli were either read incorrectly or left unread. The reading errors included adjectives, possessive adjectives, conjunctions and verbs.^[4]

The dual route cascaded model

Patients with phonological dyslexia have problem reading non-words and unfamiliar words. According to the dual route model, patients with phonological dyslexia use route 2 or 3 that have intact orthographic input lexicon which allow them to pronounce familiar words whether regular or irregular. However, due to phonological dyslexia they are unable to use grapheme-phoneme conversion (Route 1), as route 1 is impaired, thus patients find it difficult to pronounce unfamiliar words and non-words.^[10]

Related Research Articles

Aphasia Inability to comprehend or formulate language

Aphasia is an inability to comprehend or formulate language because of damage to specific brain regions. The major causes are stroke and head trauma; prevalence is hard to determine but aphasia due to stroke is estimated to be 0.1–0.4% in the Global North. Aphasia can also be the result of brain tumors, brain infections, or neurodegenerative diseases.

Dyslexia, also known as reading disorder, is a disorder characterized by reading below the expected level for their age. Different people are affected to different degrees. Problems may include difficulties in spelling words, reading quickly, writing words, "sounding out" words in the head, pronouncing words when reading aloud and understanding what one reads. Often these difficulties are first noticed at school. When someone who previously could read loses their ability, it is known as alexia. The difficulties are involuntary and people with this disorder have a normal desire to learn. People with dyslexia have higher rates of attention deficit hyperactivity disorder (ADHD), developmental language disorders, and difficulties with numbers.

In neuroscience and psychology, the term language center refers collectively to the areas of the brain which serve a particular function for speech processing and production. Language is a core system, which gives humans the capacity to solve difficult problems and provides them with a unique type of social interaction. Language allows individuals to attribute symbols to specific concepts and display them through sentences and phrases that follow proper grammatical rules. Moreover, speech is the mechanism in which language is orally expressed.

Agnosia is the inability to process sensory information. Often there is a loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective nor is there any significant memory loss. It is usually associated with brain injury or neurological illness, particularly after damage to the occipitotemporal border, which is part of the ventral stream. Agnosia only affects a single modality, such as vision or hearing. More recently, a top-down interruption is considered to cause the disturbance of handling perceptual information.

Agraphia is an acquired neurological disorder causing a loss in the ability to communicate through writing, either due to some form of motor dysfunction or an inability to spell. The loss of writing ability may present with other language or neurological disorders; disorders appearing commonly with agraphia are alexia, aphasia, dysarthria, agnosia, acalculia and apraxia. The study of individuals with agraphia may provide more information about the pathways involved in writing, both language related and motoric. Agraphia cannot be directly treated, but individuals can learn techniques to help regain and rehabilitate some of their previous writing abilities. These techniques differ depending on the type of agraphia.

Anomic aphasia is a mild, fluent type of aphasia where individuals have word retrieval failures and cannot express the words they want to say. Anomia is a deficit of expressive language. Anomia is a symptom of all forms of aphasia, but patients whose primary deficit is word retrieval are diagnosed with anomic aphasia. Individuals with aphasia who display anomia can often describe an object in detail and maybe even use hand gestures to demonstrate how the object is used, but cannot find the appropriate word to name the object. Patients with anomic aphasia have relatively preserved speech fluency, repetition, comprehension, and grammatical speech.

Associative visual agnosia is a form of visual agnosia. It is an impairment in recognition or assigning meaning to a stimulus that is accurately perceived and not associated with a generalized deficit in intelligence, memory, language or attention. The disorder appears to be very uncommon in a "pure" or uncomplicated form and is usually accompanied by other complex neuropsychological problems due to the nature of the etiology. Afflicted individuals can accurately distinguish the object, as demonstrated by the ability to draw a picture of it or categorize accurately, yet they are unable to identify the object, its features or its functions.

Semantic dementia (SD), also known as semantic variant primary progressive aphasia (svPPA), is a progressive neurodegenerative disorder characterized by loss of semantic memory in both the verbal and non-verbal domains. However, the most common presenting symptoms are in the verbal domain. Semantic dementia is a disorder of semantic memory that causes patients to lose the ability to match words or images to their meanings. However, it is fairly rare for patients with semantic dementia to develop category specific impairments, though there have been documented cases of it occurring. Typically, a more generalized semantic impairment results from dimmed semantic representations in the brain.

Primary progressive aphasia Medical condition

Primary progressive aphasia (PPA) is a type of neurological syndrome in which language capabilities slowly and progressively become impaired. As with other types of aphasia, the symptoms that accompany PPA depend on what parts of the left hemisphere are significantly damaged. However, unlike most other aphasias, PPA results from continuous deterioration in brain tissue, which leads to early symptoms being far less detrimental than later symptoms. Those with PPA slowly lose the ability to speak, write, read, and generally comprehend language. Eventually, almost every patient becomes mute and completely loses the ability to understand both written and spoken language. Although it was first described as solely impairment of language capabilities while other mental functions remain intact, it is now recognized that many, if not most of those with PPA experience impairment of memory, short-term memory formation and loss of executive functions. It was first described as a distinct syndrome by M.‑Marsel Mesulam in 1982. Primary progressive aphasias have a clinical and pathological overlap with the frontotemporal lobar degeneration (FTLD) spectrum of disorders and Alzheimer's disease. However, PPA is not considered synonymous to Alzheimer's disease due to the fact that, unlike those affected by Alzheimer's disease, those with PPA are generally able to maintain the ability to care for themselves, remain employed, and pursue interests and hobbies. Moreover, in diseases such as Alzheimer's disease, Pick's disease, and Creutzfeldt-Jakob disease, progressive deterioration of comprehension and production of language is just one of the many possible types of mental deterioration, such as the progressive decline of memory, motor skills, reasoning, awareness, and visuospatial skills.

A reading disability is a condition in which a person displays difficulty reading. Examples of reading disabilities include: developmental dyslexia, alexia, and hyperlexia.

Auditory verbal agnosia (AVA), also known as pure word deafness, is the inability to comprehend speech. Individuals with this disorder lose the ability to understand language, repeat words, and write from dictation. Some patients with AVA describe hearing spoken language as meaningless noise, often as though the person speaking was doing so in a foreign language. However, spontaneous speaking, reading, and writing are preserved. The maintenance of the ability to process non-speech auditory information, including music, also remains relatively more intact than spoken language comprehension. Individuals who exhibit pure word deafness are also still able to recognize non-verbal sounds. The ability to interpret language via lip reading, hand gestures, and context clues is preserved as well. Sometimes, this agnosia is preceded by cortical deafness; however, this is not always the case. Researchers have documented that in most patients exhibiting auditory verbal agnosia, the discrimination of consonants is more difficult than that of vowels, but as with most neurological disorders, there is variation among patients.

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Deep dyslexia is a form of dyslexia that disrupts reading processes. Deep dyslexia may occur as a result of a head injury, stroke, disease, or operation. This injury results in the occurrence of semantic errors during reading and the impairment of nonword reading.

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Brian Lewis Butterworth FBA is emeritus professor of cognitive neuropsychology in the Institute of Cognitive Neuroscience at University College London, England. His research has ranged from speech errors and pauses, short-term memory deficits, reading and the dyslexias both in alphabetic scripts and Chinese, and mathematics and dyscalculia. He has also pioneered educational neuroscience, notably in the study of learners with special educational needs.

The history of dyslexia research spans from the late 1800s to the present.

Dyslexia is a reading disorder wherein an individual experiences trouble with reading. Individuals with dyslexia have normal levels of intelligence but can exhibit difficulties with spelling, reading fluency, pronunciation, "sounding out" words, writing out words, and reading comprehension. The neurological nature and underlying causes of dyslexia are an active area of research. However, some experts believe that the distinction of dyslexia as a separate reading disorder and therefore recognized disability is a topic of some controversy.

Surface dyslexia is a type of dyslexia, or reading disorder. According to Marshall & Newcombe's (1973) and McCarthy & Warrington's study (1990), patients with this kind of disorder cannot recognize a word as a whole due to the damage of the left parietal or temporal lobe. Individuals with surface dyslexia are unable to recognize a word as a whole word and retrieve its pronunciation from memory. Rather, individuals with surface dyslexia rely on pronunciation rules. Thus, patients with this particular type of reading disorder read non-words fluently, like "yatchet", but struggle with words that defy pronunciation rules. For example, a patient with surface dyslexia can correctly read regular words like "mint", but will err when presented a word that disobeys typical pronunciation rules, like "pint". Often, semantic knowledge is preserved in individuals with surface dyslexia.

The dual-route theory of reading aloud was first described in the early 1970s. This theory suggests that two separate mental mechanisms, or cognitive routes, are involved in reading aloud, with output of both mechanisms contributing to the pronunciation of a written stimulus.

Carlo Semenza is an Italian neuropsychologist and cognitive neuroscientist. Carlo Semenza’s research activity mostly contributed to the field of aphasiology, neuropsychology of language, and numerical cognition.

References

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↑ Kendall, Diane L.; McNelil, Malcolm R.; Small, Steven L. (1998-07-01). "Rule-based treatment for acquired phonological dyslexia". Aphasiology. 12 (7–8): 587–600. doi:10.1080/02687039808249560. ISSN 0268-7038.