Aphasia
Loss of language function is called aphasia – strictly dysphasia when there is partial language loss, but the term ‘aphasia’ is commonly used for all types of language loss. Aphasia is diagnosed when there are language difficulties that occur in the absence of sensory impairments or thought disturbances – in other words, the symptoms are specific to language. The traumatic event of a stroke often results in an inability to use language to some degree, and is a sadly common occurrence. Strokes (cerebrovascular accidents) affecting those parts of the brain that support language processing account for 85 per cent of aphasia cases.
The left hemisphere has long been known to be associated with language function. Damage the left hemisphere, and language dysfunction is likely to result. In particular, two areas of the brain have long been associated with specific aphasic symptoms: Broca’s area, and Wernicke’s area.
Broca’s aphasia (or production aphasia) Broca’s area is found to be damaged in patients with Broca’s aphasia. These patients have difficulty in the production of language, some being unable speak at all, others only with difficulty. When language is produced, it lacks fluency and is slow. Speech may consist of just one or two words, with no grammar and often an absence of verbs necessary for the production of well-formed sentences. Broca’s aphasics can understand language, though. This is demonstrated by their capacity to follow instructions or to verify whether scenes match sentences.
Wernicke’s aphasia (or sensory aphasia) Patients with Wernicke’s aphasia have a problem in comprehending the speech of others, and although they can produce a fluent flow of speech, it is usually garbled, containing many pseudo-words (so-called jargon). Because they cannot understand the speech of others, they also may not be aware that they are not making sense. They suffer from word retrieval deficits and cannot properly pars sentences. These effects result from lesions to Wernicke’s area.
Other types of aphasia include the debilitating global aphasia, in which heard speech cannot be comprehended or even repeated, there is no capacity to produce speech, and even objects cannot be named. Another category is conduction aphasia, in which patients have an apparently normal capacity to understand and produce speech. But they have difficulty repeating word-strings and ‘nonsense’ words. This condition has been attributed to damage to fibres connecting Broca’s and Wernicke’s areas. Psychologists who study the changes that occur in aphasia will explore specifics, such as whether the patient has difficulty finding the right words in normal speech, repeating words and sentences, using grammar so that they can understand sentences, or producing grammatical outputs themselves. For further information on treatments of aphasia, see Zurif and Swinney (1994).
Dyslexia
Dyslexia means impaired reading. There are two broad categories: acquired dyslexia and developmental dyslexia.
1. Acquired dyslexia Brain damage in people who could previously read well can lead to acquired dyslexia. There are four main classes of this disorder:
1. People with visual form dyslexia might not be able to recognize all the individual letters. So they might read ‘mat’ as ‘cat’.
2. Those with phonological dyslexia have difficulty reading pronounceable pseudo words, like ‘pleke’, but they are good at reading real words. This shows that their problem is caused by damage to the mechanism that connects how a word looks (its orthography) to how it sounds (its phonology). By contrast, when they read well known real words, these patients can use direct routes between the whole word pattern and its sound – these direct routes are established when we learn to read.
3. Surface dyslexia is the opposite way round to phonological dyslexia. People with this disorder are unable to use this direct route to recognize words on the basis of their overall appearance, but they can read words by using orthographic knowledge. This means that they make errors pronouncing words that are irregular in the mapping between the letters and the sound, like ‘pint’ or ‘yacht’.
4. Deep dyslexia forms a very interesting category. On being asked to repeat concrete nouns, such as ‘uncle’, the patient may say ‘aunt’ instead: i.e. they substitute a semantically related item. These patients cannot read abstract words and pronounceable pseudo words. Deep dyslexia is associated with widespread left hemisphere damage, and tends to co-occur with aphasia.
2 Developmental dyslexia This refers to a developmental difficulty with reading, despite adequate intelligence. Attempts to match the reading difficulties to the categories of acquired dyslexia have led the division of syndromes into two main types: those associated with difficulties in ‘sounding out’ (as in acquired phonological dyslexia) and those related to difficulties in recognizing word forms (as in surface dyslexia). But one prevalent problem for most developmental dyslexics is poor phonological awareness: so they perform badly on tests of rhyme awareness, segmenting words into individual sounds (spelling out) and producing rhymes. The detailed study of dyslexia entails the application of well developed psycholinguistic techniques. For a review of one hundred years of work in this area, see Miles and Miles (1999).
Loss of language function is called aphasia – strictly dysphasia when there is partial language loss, but the term ‘aphasia’ is commonly used for all types of language loss. Aphasia is diagnosed when there are language difficulties that occur in the absence of sensory impairments or thought disturbances – in other words, the symptoms are specific to language. The traumatic event of a stroke often results in an inability to use language to some degree, and is a sadly common occurrence. Strokes (cerebrovascular accidents) affecting those parts of the brain that support language processing account for 85 per cent of aphasia cases.
The left hemisphere has long been known to be associated with language function. Damage the left hemisphere, and language dysfunction is likely to result. In particular, two areas of the brain have long been associated with specific aphasic symptoms: Broca’s area, and Wernicke’s area.
Broca’s aphasia (or production aphasia) Broca’s area is found to be damaged in patients with Broca’s aphasia. These patients have difficulty in the production of language, some being unable speak at all, others only with difficulty. When language is produced, it lacks fluency and is slow. Speech may consist of just one or two words, with no grammar and often an absence of verbs necessary for the production of well-formed sentences. Broca’s aphasics can understand language, though. This is demonstrated by their capacity to follow instructions or to verify whether scenes match sentences.
Wernicke’s aphasia (or sensory aphasia) Patients with Wernicke’s aphasia have a problem in comprehending the speech of others, and although they can produce a fluent flow of speech, it is usually garbled, containing many pseudo-words (so-called jargon). Because they cannot understand the speech of others, they also may not be aware that they are not making sense. They suffer from word retrieval deficits and cannot properly pars sentences. These effects result from lesions to Wernicke’s area.
Other types of aphasia include the debilitating global aphasia, in which heard speech cannot be comprehended or even repeated, there is no capacity to produce speech, and even objects cannot be named. Another category is conduction aphasia, in which patients have an apparently normal capacity to understand and produce speech. But they have difficulty repeating word-strings and ‘nonsense’ words. This condition has been attributed to damage to fibres connecting Broca’s and Wernicke’s areas. Psychologists who study the changes that occur in aphasia will explore specifics, such as whether the patient has difficulty finding the right words in normal speech, repeating words and sentences, using grammar so that they can understand sentences, or producing grammatical outputs themselves. For further information on treatments of aphasia, see Zurif and Swinney (1994).
Dyslexia
Dyslexia means impaired reading. There are two broad categories: acquired dyslexia and developmental dyslexia.
1. Acquired dyslexia Brain damage in people who could previously read well can lead to acquired dyslexia. There are four main classes of this disorder:
1. People with visual form dyslexia might not be able to recognize all the individual letters. So they might read ‘mat’ as ‘cat’.
2. Those with phonological dyslexia have difficulty reading pronounceable pseudo words, like ‘pleke’, but they are good at reading real words. This shows that their problem is caused by damage to the mechanism that connects how a word looks (its orthography) to how it sounds (its phonology). By contrast, when they read well known real words, these patients can use direct routes between the whole word pattern and its sound – these direct routes are established when we learn to read.
3. Surface dyslexia is the opposite way round to phonological dyslexia. People with this disorder are unable to use this direct route to recognize words on the basis of their overall appearance, but they can read words by using orthographic knowledge. This means that they make errors pronouncing words that are irregular in the mapping between the letters and the sound, like ‘pint’ or ‘yacht’.
4. Deep dyslexia forms a very interesting category. On being asked to repeat concrete nouns, such as ‘uncle’, the patient may say ‘aunt’ instead: i.e. they substitute a semantically related item. These patients cannot read abstract words and pronounceable pseudo words. Deep dyslexia is associated with widespread left hemisphere damage, and tends to co-occur with aphasia.
2 Developmental dyslexia This refers to a developmental difficulty with reading, despite adequate intelligence. Attempts to match the reading difficulties to the categories of acquired dyslexia have led the division of syndromes into two main types: those associated with difficulties in ‘sounding out’ (as in acquired phonological dyslexia) and those related to difficulties in recognizing word forms (as in surface dyslexia). But one prevalent problem for most developmental dyslexics is poor phonological awareness: so they perform badly on tests of rhyme awareness, segmenting words into individual sounds (spelling out) and producing rhymes. The detailed study of dyslexia entails the application of well developed psycholinguistic techniques. For a review of one hundred years of work in this area, see Miles and Miles (1999).
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