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Speech and Language Disorders

How have neurophysiological and neuroimaging techniques advanced our knowledge and understanding of speech and language disorders like agrammatism and lexical semantic disorders, as well as in thought disordered speech and dyslexia?

Term Paper (Advanced seminar) 2009 10 Pages

English Language and Literature Studies - Linguistics

Excerpt

Table of Contents

1. Introduction

2. Neurophysiological and Neuroimaging Techniques

3. Aphasia and Agrammatism

4. Dyslexia

5. Thought Disordered Speech – Schizophrenia

6. Conclusion

7. Bibliography

1. Introduction

Language is the specific human form of communication. In this process, ideas, thoughts, and conclusions can be provided verbally or in writing. Hence, language is medium through which people communicate and it serves as a means of orientation for an individual in his/her environment, which is characterized by visual and aural inputs.

Language comprehension and language processing, due to their complexity, belong to higher brain functions, which are objects of research in lots of different disciplines. The technical methods of neurophysiology have been in extensive progress since the 1950s. These methods enable researchers to examine the functions of brain activities, such as language processes. This neurophysiological progress also supports the research of speech and language disorders, such as aphasia and agrammatism, dyslexia, and thought disordered speech (as in schizophrenia). As a consequence, causes of the disorders and possible therapies (i.e., if they are successful or not) are studied.

The presented essay deals with the topic, how neurophysiological and neuroimaging techniques have advanced our knowledge and understanding of speech and language disorders, especially of lexical semantic disorders (aphasia including agrammatism), as well as thought disordered speech (schizophrenia) and dyslexia. In order to discuss this issue, the theoretical background of these disorders will be considered to discuss the functions of the respective techniques in each case. The techniques are briefly described in advance to provide the basis for the discussion.

2. Neurophysiological and Neuroimaging Techniques

In the field of language, language comprehending and the processing of perceived information has been analysed by neurophysiological and neuroimaging techniques. First of all, scientists make use of event-related potentials (ERP), which are deduced by the help of electroencephalography (EEG). ERPs are either evoked by sensory perception or correlated to cognitive processes such as language processing. According to Wassenaar (2004: 553), “[…] ERPs are small voltage changes in the EEG, recorded at the scalp and time-locked to the onset of a particular event (e.g., the onset of words in a sentence).” The analysis of these potentials is useful in the research of aphasia and agrammatism or of thought disordered speech.

In order to examine dyslexia, scientists exploit, for example, functional magnetic resonance imaging (fMRI). fMRI is a neuroimaging technique to illustrate brain activity, which developed from magnetic resonance imaging (MRI). It enables scientists to visualise metabolic processes caused by brain activity. Thus, the location of the activity in the brain can be calculated. (Scott 2003: 13f)

3. Aphasia and Agrammatism

In the second half of the 19th century, Paul Broca, a French anthropologist and doctor, was able to prove that the left hemisphere (usually the dominant one) of the human brain is the centre of speech, “[…] more precisely […] the left inferior frontal gyrus.” (Scott et al. 2003: 7) According to the researcher, this part of the brain, today known as Broca’s area, is responsible for the production of speech. This also includes the encoding of speech (e.g., grammar), as well as the use of function words and phonological rules. With the help of this knowledge, in 1874 the German neurologist Karl Wernicke identified another area in the left hemisphere, which plays an important role in the comprehension of language: the so called Wernicke’s area. Both areas are linked to each other through the arcuate fasciculus. (Scott et al. 2003: 7) Briefly spoken, in order to answer a heard question, the input is perceived by the auditory cortex and comprehended in Wernicke’s area. The response is controlled in Broca’s area, because this part controls the language production. Finally, the motor cortex, which is responsible for all movements, including those of speech organs, coordinates the spoken output.

Aphasia is usually the result of a lesion on the left hemisphere, especially on the above described areas. Hence, this disorder affects the speech of the patient. The word aphasia etymologically derived from the Greek term αφασία, which originally means “without language”. It is a lexical semantic disorder due to a neurological injury, e.g. a stroke, traumatic brain injury, cerebral haemorrhage, or tumours, that occurs after finished language acquisition. It causes impairments of several language modalities such as oral speech, language comprehension, writing, or reading in different severities.

Common types of aphasia are Broca’s aphasia (influencing language production) and Wernicke’s aphasia (concerning language comprehension), both caused by a lesion on their respective areas, and anomia, a lexical semantic disorder and a typical symptom of all kinds of aphasia. These disorders are not results of impairments of the intellectual, psychiatric, or sensory skills.

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Details

Pages
10
Year
2009
ISBN (eBook)
9783656319672
ISBN (Book)
9783656324256
File size
478 KB
Language
English
Catalog Number
v205523
Institution / College
University of Wales, Bangor
Grade
B
Tags
dylexia neuropsychological neuroimagingknowledgedisorder lesion aphasia agrammatismlexical semantic disordered Aphasie Agrammatismus Sprachbehinderung brain Hirn Gehirn Messung Hirnstrommessung Schizophrenie schizophrenia

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Title: Speech and Language Disorders