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Language Disorder (1)(1).pptx

  1. Language and the Brain By Dr. Rehab Farouk An Introduction to Psycholinguistics Danny D. Steinberg and Natalia V. Sciarini
  2. The Brain • A whole which is divided into vertical halves that seem to be mirror images of one another. It looks much like a walnut with the two parts joined around the middle, except that there is little space between the two halves in the real brain. Each half of the brain is called a hemisphere. There is a left hemisphere and a right hemisphere. The hemispheres come out of the brain stem, which connects to the spinal cord. The hemispheres maintain connection with one another through a bundle of fibres called the corpus callosum. The brain, together with the spinal cord, is referred to as the central nervous system of the human body.
  3. The cerebral cortex • There is a covering on each hemisphere, called the cortex, which is a furrowed outer layer of cell matter. It is the cortex that is concerned with higher brain functions in both humans and animals. The cerebral cortex in humans has increased in size and complexity to become the largest part of the brain. • Each cerebral hemisphere is divided into four parts or lobes: from front to back there are the frontal, temporal, parietal (located above the temporal), and the occipital. This division of the brain into lobes is loosely based on physical features and not on actual separations.
  4. General Functions • General functions such as cognition (to some degree) occur in the frontal lobe, hearing occurs in the temporal lobe, general somaesthetic sensing (feeling in the arms, legs, face, etc.) in the parietal lobe, and vision in the occipital lobe. Each hemisphere has these lobes with these functions. As we shall see later, there are other hemispheric-specific functions that are also located in some of these areas. For example, the left hemisphere typically involves language.
  5. Language areas: The front part of the parietal lobe, along the fissure of Rolando, is primarily involved in the processing of sensation, and may be connected with the speech and auditory areas at a deeper level. l The area in front of the fissure of Rolando is mainly involved in motor functioning, and is thus relevant to the study of speaking and writing.  l An area in the upper back part of the temporal lobe, extending upwards into the parietal lobe, plays a major part in the comprehension of speech. This is ‘Wernicke’s area’. l In the upper part of the temporal lobe is the main area involved in auditory reception, known as ‘Heschl’s gyri’, after the Austrian pathologist R. L. Heschl (1824–81).  l The lower back part of the frontal lobe is primarily involved in the encoding of speech. This is ‘Broca’s area
  6. Spoken Language • Some of the neural pathways that are considered to be involved in the processing of spoken language: • 1. Speech production. The basic structure of the utterance is thought to be generated in Wernicke’s area and is sent to Broca’s area for encoding. The motor programme is then passed on to the adjacent motor area, which governs the articulatory organs. • 2. Reading aloud. The written form is first received by the visual cortex, then transmitted via the angular gyrus to Wernicke’s area, where it is believed to be associated with the auditory representation. The utterance structure is then sent on to Broca’s area, as in (1). • 3. Speech comprehension. The signals arrive in the auditory cortex from the ear, and are transferred to the adjacent Wernicke’s area, where they are interpreted.
  7. Hemispheres • Left and right hemispheres control opposite sides of the body. • Dysfunctions seem to be caused by the two hemispheres vying with one another for dominance. Some even argue that left-handers die younger (Halpern and Coren, 1991). • Because dominance is a congenital condition, the practice of forcing children who are naturally left-handers to use their right hand for writing, etc., will not remedy such problems but may serve to worsen them and create others. Many countries still force natural left-handers to be right-handers
  8. Left-handers • About 10 per cent of the population worldwide are left- handed but, • counter to expectations, only about 30 per cent of left- handers have righthemisphere dominance (Klar, 1999). • The majority of left-handers are lefthemisphere dominant but their dominance tends to be much less marked than in natural right-handed persons. • The lack of strong dominance for lefthanders is believed to be a factor contributing to speech disorders and to various reading and writing dysfunctions, such as stuttering and dyslexia, which includes the reversal or mirror-imaging of letters and words when reading or writing. Lamm and Epstein (1999)
  9. Sound preferences Explain the relation between the two hemispheres and the different sounds. • Speech sounds are differentiated from other types of sounds including music, animal sounds, and noises. • . The two hemispheres specialize in processing these two types of sounds (speech and non-speech). • right-handers, speech sounds are mainly processed in the left hemisphere while music, noises, and animals sounds are mainly processed in the right hemisphere. • The opposite will be the case for some left-handers. • Because of the nature of the arrangement of large and small bundles of fibres, right-handed persons with lateralization for language in the left hemisphere will perceive speech sounds more readily through the right ear than the left.
  10. Listening behind a closed door if you are a right-hander, is: ‘Right ear forward’. This is because (1) speech sounds are processed in the left hemisphere, (2) the first big impulse of speech sound will be transmitted to the left hemisphere from the right ear. • (3) the first big impulse will precede and dominate any other big impulse.
  11. Pierre Paul Broca • He was a French pathologist and neurosurgeon (1824–80) • who made the first great discovery regarding brain and language. He discovered a certain area of the cortex that is involved with the production of speech; that part of the cortex bears his name, Broca’s area. • The speech-production process would begin in Broca’s area, pass on through the arcuate fasciculus to the motor area and from there to the articulators of speech for vocalization.
  12. Wernicke Area Carl Wernicke, a German neurologist (1848–1905) According to Wernicke, on hearing a word, the sound of a word goes from the ear to the auditory area and then to Wernicke’s area. It is from Broca’s area that the vocalization of speech would then be activated
  13. Reading (see Figure 12.1). When a word is read, according to Wernicke, the information goes from the eyes to the visual area of the cortex in the occipital lobe, from there to the angular gyrus, then to Wernicke’s area and then to Broca’s area, which causes the auditory form of the word to be activated. Wernicke had the mistaken belief that all written words had somehow to be speech activated (said aloud).
  14. Left Hemisphere Although most language processes occur in Broca’s area, Wernicke’s area, and the angular gyrus, some language functioning occurs elsewhere in the left hemisphere, as well, and some even occurs in the right hemisphere. The ability to understand the meaning of intonation, such as the rising tone of a question, the ability to interpret emotional intentions, such as anger or sarcasm, from inflections in the voice, and the ability to appreciate social meanings from something such as whispering, may very well be located outside of what have been traditionally regarded as the main language areas of the brain.
  15. Right-Hemisphere • There is increasing evidence that the right hemisphere is critical for understanding discourse (Hough, 1990; Kaplan et al., 1990; Beeman, 1993, 1998; Brownell and Martino, 1998; Stemmer and Joanette, 1998; Paradis, 2003). • Thus, patients with right-hemisphere damage have impairments concerning narrative script, interpretation, integration of information or conceptualization of the unit as a whole, construction of new conceptual models, and inferences about another person’s beliefs and intentions (Stemmer and Joannett, 1998).
  16. What happens with the damage of the right hemisphere? • The right hemisphere has an ability to use ‘knowledge of the world’, involved in scripting, where a number of sentences are related to a topic. • Patients who have damage in their right hemisphere show structuring problems in story recall (Moya et al., 1986), and their speech is disrupted, particularly at the level of discourse, jumping from one topic to another incoherently (Brownell and Martino, 1998).
  17. The right hemisphere can take over left- hemisphere functions. • damage to language areas in the left hemisphere of young children is compensated for, with the right hemisphere taking over the reacquisition of language.
  18. Bilingualism • Albert and Obler (1978), Karanth and Rangmani (1988), and Wuillemin et al. (1994) report greater involvement of the right hemisphere in bilinguals than in monolinguals. Albert and Obler (1978) argue that ‘the right hemisphere plays a major role in the learning of a second language, even in adulthood’ (p. 243)
  19. Sign Language • Right-handed deaf signers, like hearing persons, exhibit aphasia when critical left-hemisphere areas are damaged (Poizner et al., 1989) • Approximately one dozen case studies provide sufficient detail to implicate left-hemisphere structures in sign-language disturbances.
  20. Language Disorder • language disorders, known as aphasias, are presumed to have as their cause some form of damage to some specific site in the hemisphere where language is located. Such damage causes characteristic problems in speech, as well as in reading and writing.
  21. Broca's Aphasia • One particular condition, now called Broca’s aphasia, is characterized by meaningful but shortened speech and also occurs in writing. In the condition, grammatical inflections are often lacking, such as the third-person present tense ‘-s’ (‘Mary want candy’ for ‘Mary wants candy’), and the auxiliary ‘be’ (‘Joe coming’ for ‘Joe is coming’), as are articles, prepositions, and other so- called function words. In a way, the speech is similar to that of children at the telegraphic stage of speech production. • Although the most noted feature of Broca’s aphasia is the fragmentary nature of speech production, it has recently been discovered that speech • comprehension is also affected. In one experiment with a patient with Broca’s aphasia, when presented with the spoken sentence, ‘The apple that the boy is eating is red’, the patient was able to understand the sentence,particularly with regard to who was doing the eating (the boy). However, whenpresented with the sentence, ‘The girl that the boy is looking at is tall’, the samepatient could not figure out who was doing the looking (the boy).
  22. Wernicke’s aphasia • This condition is characterized by speech that often resembles what is called nonsense speech or double-talk. It sounds right and is grammatical but it is meaningless. It can seem so normal that the listener thinks that he or she has somehow misheard what was said, as is often the case in ordinary conversation. A patient with Wernicke’s aphasia may say, ‘Before I was in the one here, I was over in the other one. My sister had the department in the other one’, ‘My wires don’t hire right’, or ‘I’m supposed to take everything from the top so that we do four flashes of four volumes before we get down low’.
  23. Word substitution • Patients with Wernicke’s aphasia commonly provide substitute words for the proper ones on the basis of similar sounds, associations, or other features. The word ‘chair’, for example, elicited the following in some patients: ‘shair’ (similar sound), ‘table’ (association), ‘throne’ (related meaning), ‘wheelbase’ (?) and ‘You sit on it. It’s a . . .’ (word loss). As with Broca’s aphasia, Wernicke’s aphasia can also cause a severe loss of speech understanding, although the hearing of non-verbal sounds and music may be unimpaired
  24. Reading and writing aphasias: dyslexias • One type of aphasia that involves disorders in reading and writing is called dyslexia. There are many sorts of dyslexia, one category of which is due to damage to the brain, after reading and writing have been acquired. With children, however, dyslexias may be observed while they are in the process of acquiring reading and writing skills. Problems of hemisphericdominance or defects in visual perception, for example, may play some role in causing difficulties in reading and writing. Some children may only be able to write backwards (deer as reed) or upside down, or in reading they may confuse letters (b with d, p with q, u with n, m with w) and engage in other anomalies.