# Psycholinguistics/Aphasia
## Introduction

Aphasia is a language disorder caused by damage suffered to certain portions of the brain that are involved in language perception and production. Depending upon the area that is affected, a person suffering from Aphasia may be able to speak fluently but not coherently, and vice versa. Aphasiology is the study of these linguistic deficits resulting from brain damage and through this study, much can be learned and inferred about the normal function of language and its organization within the brain. There are a variety of modern assessment tools through which aphasia can be studied in patients. The prognosis varies greatly and is dependent upon such factors as, site of the stroke, severity of the lesion, the age of the patient, and the type of aphasia acquired.

## History

The word “Aphasia” is derived from the Greek word “aphatos”, meaning speechless. Mentions of Aphasia in Greek Medicine are evident in which speechlessness accompanied convulsions are documented as resulting in paralysis of the right side of the body. Aphasia is again shown in literature from the Roman times in which authors such as Soranus of Ephesus noted the impairment of speech following paralysis of one part of the body. Great advancements occurred from the 1800s to the 1860s in which clinical knowledge, theoretical formulation and neuropathology were developed and a working knowledge of the brain as associated with speech disorders was beginning to be understood more scientifically.
The most recent widespread acceptance of the brain's functioning is in the language localization theory in which different sections of the brain are responsible for the functioning of different bodily functions. The birth of this concept came with Franz Joseph Gall's theory of phrenology. Gall proposed that all mental functioning could be located on different sections of the brain and the advancement of a particular area resulted in a visible difference on a person's head. Although Franz Gall's theory of phrenology is now considered a pseudoscience, his localizationist assumptions were evidently working in the right direction as it is now possible to scientifically prove that certain sections of the brain are involved in different bodily functions.
The theory of language localization gained furthur credit with significant findings attributed to Paul Broca in the 1860s. The beginning of comprehensive Aphasia understanding came with Paul Broca’s research and subsequent description of his patient Laborgne's brain. In 1861, Broca published “Remarques sur le siège de la faculté du langage articulé: suivies d' une observation d'aphémie” in which he evidences for the localization of articulate speech in the frontal lobe. Upon Leborgne’s death, Broca performed an autopsy and determined that the damage was suffered to the third convolution of the left frontal lobe, which is now commonly referred to as Broca’s area. Stemming from his influential findings, was a revolution in medical and physioogical thinking as it pertained to the brain and the establishment of cerebral localization. Less than a decade later, Wernicke identified “sensory” aphasia as being localized to the temporal lobe. Ludwig Lichtheim then branched off of Wernicke’s model, naming five other types of aphasia, pure word deafness, conduction aphasia, apraxia of speech, transcortical motor aphasia, and transcortical sensory aphasia.
As the mid 20th century approached, professionals specializing in language began searching for a revised model of understanding normal and abnormal language functioning. One professional by the name of Norman Geschwind formed the Geschwind model. Revisiting language localization theories, the model describes the interconnecting functions of a normally working human brain to produce speech and language comprehension. Aphasias were viewed as occurring along these interconnecting lines, disrupting spoken speech or comprehension, resulting in various symptoms. Although the Geschwind model was a great contribution to the understanding of language, problems with it have been uncovered in recent years and a straying away from this understanding of language functioning has occurred.
Advancements in imaging technology has propelled our understanding of the brain as it pertains to language and disorders such as aphasia. Voxel-based Lesion Symptom Mapping (VLSM) in particular, has allowed for medical professionals to determine more specifically where brain lesions lie and the tasks that are impaired because of them. VLSM's ability to identify white matter regions which can play causal roles in certain cognitive domains allows for professionals closely identify these problem regions. A 'voxel' is the three dimensional analog of a pixel and represents a volume of 1 cubic millimeter; The image produced displays 3 dimensional picture of the human brain as depicted in the picture to the right. Studies using VSLM have suggested that language functions are not as localized as the Geschwind model posits it to be.

## Forms of Aphasia

Aphasia can be divided into three category types depending upon the quality of the deficit acquired. Fluent, non-fluent, and pure:
* Fluent
    Fluent aphasias are caused by impairment to language reception. These aphasic individuals have little issue with fluent verbal output but have difficulty in the language that they are speaking, which often seems like nonsense. Some fluent aphasias include: Wernicke’s Aphasia, Conduction Aphasia, and Anomic Aphasia.
* Non-fluent
    Non-fluent aphasias are impaired in their ability to articulate. Unlike some fluent aphasias, non-fluent aphasics retain a relatively intake auditory verbal comprehension. Some examples of non-fluent aphasias include: Broca’s aphasia, Transcortical motor aphasia, and global aphasia.
* Pure-Aphasia
    Pure aphasias display themselves as selective deficits to writing, reading or the recognition of words altogether. Pure aphasias include: Pure alexia, Pure word deafness, and Agraphia.

## Types of Aphasia
### Broca's Aphasia

    Broca's aphasia, also referred to as 'expressive aphasia, occurs as a result of damage to the frontal lobe of the brain. As a result of the deletion of function words (i.e. 'and', 'the'), speech by a Broca's aphasic appears telegraphically. As opposed to wernicke's aphasia, speech is nonfluent, and highly laboured depending upon the severity of the aphasia.

### Global Aphasia

    This type of aphasia is a result of extensive damage to the language areas of the brain with the impairments appearing globally across all areas of speech processing and production.

### Transcortical Motor Aphasia (TMA)

    Patients with TMA, also referred to as adynamic aphasia, display nonfluent speech as well as phonemic and global paraphasias and the omission of function words. This aphasia results from damage, typically caused by a stroke, of the anterior superior frontal lobe.

### Wernicke's Aphasia

    Wernicke’s Aphasia occurs as a result of damage to the temporal lobe of the brain. Patients exhibit fluent speech and paraphasias and in some types are unable to comprehend speech as well as produce comprehensible speech.

### Conduction Aphasia

    Conduction aphasia, also referred to as 'associative aphasia', is a fluent disorder caused by damage to the left hemisphere of the brain above and below the posterior sylvian fissure. Auditory comprehension remains fairly intact in these individuals, with speech production being mostly affected. Speech repetition is poor, and spontaneous speech production is laboured, with frequent substitution of words or transposing of sounds. As opposed to wernicke's aphasia, patients with conduction aphasia are often aware of their mistakes and make efforts at correcting their errors.

### Anomic Aphasia

    Anomic aphasia occurs as a result of damage to the language areas outside the perisylvian circle. Characteristic of this aphasia is difficulty in word retrieval, while fluent and well-articulated speech remains intact.

### Transcortical Sensory Aphasia (TSA)

    TSA patients display damage to the temporal occipital parietal junction located behind Wernicke's area.
TSA differs from Wernicke's aphasia in that, although they are both fluent disorders, TSA sufferers have fluent and usually comprehensible speech, save for semantic paraphasia in which similar words are substituted for an item. Auditory comprehension is often severely impaired.
* The following table separates the different types of aphasias, identifies the area of the brain affected and then names the deficits incurred by each.
| Disorder | Site of Lesion | Spontaneous Speech | Speech Comprehension | Repetition | Naming |
| Broca’s aphasia | Left frontal cortex rostral to base of motor cortex | Nonfluent | Relatively intact | Poor | Poor |
| Global aphasia | Anterior and posterior language areas | Nonfluent | Poor | Poor | Poor |
| Transcortical motor aphasia | Areas anterior and superior to Broca’s areas | Nonfluent | Relatively intact | Intact | Poor |
| Wernicke’s aphasia | Posterior part of the superior and middle left temporal gyrus and left temporoparietal cortex | Fluent | Poor | Poor | Poor |
| Conduction Aphasia | Temporoparietal region, above and below posterior Sylvian fissure | Fluent | Relatively intact | Poor | Intact |
| Anomic Aphasia | Posterior part of the superior and middle left temporal gyrus and left temporoparietal | Fluent | Relatively intact | Intact | Poor |
| Transcortical sensory aphasia | Posterior to Wernicke’s area around boundary of occipital lobe | Fluent | Poor | Intact | Poor |
(From Biological Psychology by Klein, Stephen B., © 2000.)

## Signs and Symptoms

Individuals may experience one or many of the following symptoms of an acquired aphasia due to stroke or brain damage:
* Disturbances in Naming 'Paraphasia' :
Paraphasia refers to the inability to use correct words in speech through substitution of other words in a way that makes speech incomprehensible. In normal human speech, the ability to quickly retrieve words from a mental lexicon makes it easy for speech to sound fluid, well- structured and effortless. This process of selecting a word, termed ‘word finding’, is automatic for most of the population of normal speakers, but for aphasics displaying paraphasia, this process is greatly impaired resulting in the substitution of random words for the intended word. It is called ‘global’ aphasia when an aphasic substitutes an entire word and ‘semantic’ aphasia when a word belonging to the same semantic field is substituted.
* Disturbance of Fluency:
Aphasic patients are grouped into two categories: fluent, and non-fluent. Fluent aphasics retain the ability to speak in continuous strains of words, with the meaning of the uttered words being the point of issue. Non-fluent aphasics, such as Broca’s aphasics, suffer from low speech rate, short sentence length, with the production of sentences, and even single words being laboured.
* Disturbance of Repetition:
In some aphasia patients, the ability to repeat words may be lost. More specifically, impairment of the ability to repeat indicates that the damage to the brain is located in the perisylvian region of the dominant hemisphere. Conversely, patients suffering from transcortical aphasia repeat too frequently, and engage in a echolalia, meaning they repeat what is being said to them without knowledge that they are doing so.
* Disturbance of Grammatical Processing 'Agrammatism' :
Agrammatism refer to an aphasic’s inability to speak correctly in terms of grammatical morphemes. As a result of this, free grammatical morphemes, as well as inflectional affixes which indicate tense or aspect, are not present in speech. Sentences are oversimplified with the omission of these function words, resulting in a telegraphic speech. Also, these patients have difficulty with questions or complex sentence, such as passive sentences. The severity of the aphasia predicts the amount of errors an aphasic makes in this area.
* Disturbances of Reading and Writing:
Certain Aphasias can affect reading and/or writing as well as speech production and processing. Reading and writing are not necessarily affected together or even equally when the pairing does occur, however, in some aphasias, all of the above are affected together, only in varying degrees of intensity.
* Apraxia of Speech:
This type of Apraxia, also referred to as dyspraxia, occurs when the brain is damaged in a way that disrupts voluntary movement involved in speech production. When patients with Apraxia are asked to perform a physical command, they are unable to do so even though the command is understood and the speech muscles are not impaired due to paralysis. Two types of Apraxia exist: Acquired Apraxia of Speech, and Developmental Apraxia of Speech. The focus, as it related to Aphasia, is in acquired apraxia of speech as it is a result of sustaining injury to the central nervous system.

## Treatments

* Aphasia Rehabilitation

## Learning Exercise

1. The following youtube clips show different situations in which people suffer from aphasia. During the first segment, you encounter councilman Ken Albrecht. Given the way he speaks during therapy, what type of Aphasia does he likely have? As well, referring back to the table on the types of aphasia, what type of Aphasia does the man in the second clip suffer from?
http://www.youtube.com/watch?v=Bk13HLma2CI
http://www.youtube.com/watch?v=ZDbSh5DoVJA&feature=related
2.Refer back to the readings of this chapter. What is the primary issue with the Geschwind model?
3.Watch the following video: http://www.youtube.com/watch?v=NUTpel04Nkc
   * What qualities of Broca’s aphasia does Charles display?
   * Why is it that he has such an issue with the simple sentence concerning the leopard and the lion?
   * What types of symptoms would you be witnessing if Charles was suffering from Conduction Aphasia?
4. What does the study of Aphasias tell us about the brain and language?
5. What recent advancements have made it possible to study the brain in detail?
6. As a doctor you encounter a patient who begins to describe experiencing what you suspect to be a stroke. Upon studying their behaviour, you come to find that their fluency of speech is normal, but their ability to name things is greatly impaired and proves to be laboured and frustrating for the patient. What type of aphasia has this patient experienced? What part of the brain was likely damaged due to the stroke?
7. If the temporoparietal region of the brain is damaged, what type of aphasia is a patient suffering from and what would their symptoms be?