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Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 345 Chapter 13 Neurolinguistics Study of Language and Brain Speech is the representation of the mind, and writing is the representation of speech. Aristotle What to find in this chapter Structure of Brain Aphasia and Anomia Lateralization Dichotic Listening Mechanisms of Speech Neuro-Linguistic Programming (NLP) Teaching through Neurolinguistics 13.0 Introduction If we had to do a savage experiment on a person by mutilating him piece by piece in order to find out which bodily organ houses language faculty, what do you think the result would be? The obvious answer is head: more specifically the brain, which is contained in the head. Thankfully, with the development of sciences we need not do such an inhuman experiment to prove our point. Recall from the first chapter that one of the major features of language was that language is a product of mind and that it is produced as a result of the mental operations in the brain. In this chapter we elaborate on the relationship of language and brain so as to probe the physiological underpinnings of language: we would be pursuing questions like: Where is language located in the brain? Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 346 What are building blocks of the organ called brain? How does the nervous system function to encode and decode speech and language? This chapter begins with a description and scope of neurolinguistics, followed by brief information on the structure of brain. In the rest of the chapter, the question is investigated whether specific parts of the brain have specific functions. To support the position that it is so, various experiments and techniques are explained. Finally, three models are offered in order to account for the paths and procedures that take place during speech production. 13.1 Neurolinguistics Neurolinguistics is the term used to refer studies describing the physical relationship between language and brain. The term came about as result of the blending of the medical term ‘neurology’ and ‘linguistics’. Neurology is a branch of medicine that scientifically studies the anatomy and (mal)-functions of brain. Neurolinguistics is more a branch of neurology than of linguistics as mainstream linguistic studies usually are confined to the output, i.e. speech as produced by speakers. Therefore, neurolinguistic information is largely dependent on case studies and experiments done in neurology laboratories. There are times however when neurologists have to consult with linguists in order to appreciate the subtle differences their patients produce. For instance, they need to know what parts of speech are if they wish to better describe the type of language their patients produce, or what is phonology, morphology or syntax. 13.2 Structure of Brain Brain is no doubt the most indispensable, sensitive, and complex organ of the body. We will not go into the intricate aspects of its physical structure nor all of its functions for the human body. For our purposes, however, we will mention only those areas that are relevant for language. We know from newspaper reports that some seriously ill patients are described as “brain dead”. A brain dead patient is an otherwise fully functional person except that his brain functions are severed to a point where the patient Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 347 experiences total loss of consciousness, which is enough evidence to show that brain is the most important organ. Brain is located in the upper part of the head, protected by a spherical shape of bones known as skull. In between the bones and the brain lies a thin layer of tissues to regulate heat and cold. Brain contains about 10 billion neurons, which are the building blocks of the brain. The neurons are interconnected through billions of fibers. A neuron can be conceptualized as a nerve cell containing information of any kind. Continuous flow of oxygen through thousands of tiny veins is supplied to the brain so that brain can keep functioning normally. The size of the brain in men is generally greater in about one fifth than in women. Average brain weight for women is about 450-500 grams while it is about 550-600 grams for men. Larger brain size does not appear to play any positive or crucial role whatsoever in speech given the popular view and observation that women speak in longer durations than men. Brain cannot be conceptualized in isolation: it is part of the nervous central system that controls the body and also it is the most functional part of it. The central nervous system consists of two main organs: the spinal cord and the brain. Spinal cord can be conceptualized as the arm of the brain to control physical movements of the body and it extends through the skeleton to all areas in the body. When looked from outside, brain looks like a watermelon cut in half, which is further divided into halves, called ‘hemispheres’. The two hemispheres are connected by a cord, called ‘corpus callosum’1, which is like an electrical cable that enables the essential communication between the two hemispheres. One basic operation of the two hemispheres is that the right hemisphere controls the movements of the left part of the body while the left controls the movements of the right part of body. That is, if a serious damage is inflected in the right hemisphere, it is the left part of the body that is paralyzed or seriously handicapped. Both hemispheres work together though at times one is more involved in some mental functions while the other less. If the left hemisphere carried out more mental functions in some people, they are said to be ‘left hemisphere dominant’ and visa versa. For instance, for 95 % of right-handed people it is the left hemisphere 1 The pronunciation for it is / / Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 348 that is dominant. This relationship, however, is not symmetrical. This does not mean that the opposite holds true for left-handed people. Actually, left hemisphere is dominant for more than 60 % of left-handed people. Neurology is still in its infancy: we know very little about the functions of the brain, and research is continuously being carried out to explore the depths of the brain functions. Localization The question that whether certain parts of the brain are “assigned” certain abilities, capacities, or functions has been debated for about two centuries. If specific parts of the brain are identified having different human abilities or competencies, it is then said that certain abilities are ‘localized’ in the brain. Though there are differing views on the topic ranging from the extreme argument that all parts of the brain participate in all operations of the body to the argument that precise areas are responsible for specific functions. It appears from the more recent as well as some earlier studies that the latter view is more favorable, at least, so far as linguistic operations are concerned. Aphasia One of the pioneers of research on brain was a French surgeon named Paul Broca. He presented evidence in a conference in Paris, France, in 1861 that it is the left hemisphere with which we speak. Thus, the first piece of credible evidence was favoring the view that language functions are localized. How did he obtain evidence to show that language is localized? The patients he worked on had injuries on the front part of the left hemisphere and as a result of the injuries these patients had difficulty in expressing themselves (see figure). Their speech was like a telegraphic speech similar to what two year old children would speak. The discovery pointed to the “house” of language in the brain while it identified an impairment or physical disorder in the patient. This impairment is known as ‘aphasia’. Aphasia then can be described as a language disorder that results from damage to certain parts of the brain responsible for language functions. Aphasia can also occur either as a result of a stroke or heart attack. This type of aphasia, named Broca’s aphasia, impairs Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 Speech and Comprehension. Reading and Writing. 349 Individuals with Broca’s aphasia can still speak sensibly and in short phrases. They tend to use content words such as verbs, nouns and so forth while omitting function words such as and, the, is, and the like. The following is a typical example from aphasic speech, whose interpretation depends heavily on the context of speech. Speech of Individuals with Broca’s Aphasia Interpretation I will take the dog for a walk. Walk dog. You take the dog for a walk. The dog walked out of home. Later in 1873 another surgeon Karl Wernicke from Germany was presenting evidence relating to language disorders: but this time the location of the injuries was not the front part of the left hemisphere, but the back part of the brain. The actual area involved was slightly larger than that of Broca’s area. Speech of Individuals with Wernicke’s Aphasia Interpretation You know that smoodle pinkered and that I want to The dog needs to go out so I get him round and take care of him like you want will take him for a walk before. Wernicke’s aphasia exhibits features of speech that seem to have the opposite characteristics to those of Broca’s aphasia. Individuals with Wernicke's aphasia tend to speak in long sentences that may have no clear meaning. Though wordy their sentences are, again the circumstances under which the speech was made needs to be known well to interpret the sentences. Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 350 LEFT HEMISPHERE: Broca’s Area and Wernicke’s Area Broca’s Area FRONT BACK Wernicke’s Area BROCA’S APHASIA prevents a person from producing WERNICKE’S APHASIA loss of the ability to understand language speech person can understand language Clear but non-sensible speech words are not properly formed Longer sentences with considerable grammar Unclear pronunciation Considerable grammar with little semantics Speech is slow and broken. These two pioneering studies and many more that replicated them proved beyond doubt that language is localized in two specific areas in the left hemisphere: Broca’s area is close to the very front part while Wernicke’s area is close to the back part, though considerably larger than the previous one. Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 351 Overall, then, we are not speaking of a complete loss of linguistic capacity with the two types aphasic patients; rather, it is a partial one that blocks smooth and effective communication. Despite their injuries, they can still produce and hear language. Anomia It should then be clear that aphasic patients are unable to remember the words they wish to use. The loss of the ability, to a great extent, to call words on demand is called ‘anomia’. In such cases, aphasic speakers may replace other words or phrases to compensate the deficiency. The strategies they use reveal how their lexicon is organized in terms of pronunciation, grammar or semantics. Fromkin and Rodman (1983:366) claim, on the basis of available data from aphasic type of speech, that phonetic and phonological components of language are separate. They cite evidence in which aphasics will say democracy when they are asked to read liberty: This reveals the reality of semantic features. It is almost as if the patient in reading went to the stored written word and “looked up” its meaning and then immediately went to another word which shared these semantic features abd read that word instead. (ibid. p.366) Lateralization Dominance Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 352 The following figure is adapted from Akmajian (1984). LEFT HEMISPHERE Language Verbal Sounds Speech Reading Writing RIGHT HEMISPHERE Holistic processing Nonverbal sounds Calculation Visuospatial skills Recognition Thought Melodies Right visual field Left visual field Corpus Callosum Experiments with Brain Various experiments have been carried out to find out the exact or relative positions of linguistic functions in the brain. These experiments involve studies with patients whose corpus callosum was sectioned, injecting chemicals into the brain, electrical stimulation of the brain, and listening to two different expressions simultaneously. Dichotic Listening In dichotic listening, as the term suggests, subjects are given two pieces of listening text at the same time, one to the left ear, the other to the right ear. For Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 353 instance, subjects can be asked to report what they heard soon after they are subjected to the listening of student through the left ear and teacher through the right ear. Consider the table for the experiment results that involve the testing of verbal as well as nonverbal sounds. Verbal Sounds Nonverbal Sounds Dichotic Listening Experiments Results Listening - Left Ear Listening - Right Ear Student Teacher Book Paper Cough – cough Ahh - ahh Police siren Car horn Report Result Teacher Paper Cough – cough Police siren Generally speaking, subjects who heard teacher through the right ear and student through the left reported to have heard teacher more often. This result, coupled with others, indicated that verbal sounds are processed in the left hemisphere. When subjects are subjected to nonverbal sounds, the opposite turned out to be the case. For instance, cough – cough was spoken to the right ear while ahh – ahh was to the left ear. The result was that subjects reported to have heard better cough – cough. One can conclude from these studies that the processing of verbal sounds is carried out in the left hemisphere and the nonverbal sounds in the right, which is another piece of evidence for the existence localization or specialization in the brain. Split Brains There had to be occasions when the injured patients’ corpus callosum had to be removed to offer them some relief from pain, which produces a situation in which the communication between the left and right hemispheres is broken down. Experiments on such patients showed that information sensed by the left side of the body (which arrives at the right hemisphere for processing) cannot be verbally expressed. If an apple is put in the left hand of a split-brain human and his vision is cut off, he cannot describe the object. The right brain senses the apple, and is able to distinguish the apple from other objects, but the information cannot be relayed to the left brain for linguistic description. But if the same experiment is repeated and in addition a banana is placed in the right hand, the subject is able to describe the banana verbally, though he is still unable to describe the apple. (Fromkin and Rodman, 1983:369) Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 354 Brain Imaging Technique With the development of technological devices, the relationship between language and brain can be more accurately studied. States of the brain during linguistic activity can be “photographed” in the form of images if do not mind the term. One of these brain imaging techniques is PAT, standing for Positron Emission Tomography. Images produced by PAT show the physical activities taking place in the brain during language activity. One of these activities is that the pace of blood flow increases in those areas where language is used, either in listening or speaking. PAT images indicate that such observable changes do not only take place in the left hemisphere but also in the right. In other words, though the right hemisphere is not dominant in language, it still has a part to play in language reception and production. Chemical Injection In 1949 Wada introduced a chemical technique in determining the location of speech. In his experiment, he used a chemical called ‘sodium amytal’, which is an anesthetic to temporarily put the brain to sleep. He injected this chemical into the arteries that supply blood to both hemispheres. When he injected the chemical into the left arteries of patients who had the language ability in the left hemisphere, they could not speak when they were asked. However, the same patients could speak and answer questions when the injection was made the right arteries that supply blood to the right hemisphere. Many more similar studies confirmed that language is localized, and in most people language is localized in the left hemisphere. Electrical Stimulation Perhaps the most elaborate of a series of pioneering studies was carried out by Penfield and Roberts (1959) in Canada. They were not particularly researching the relationship between language and brain as they were trying to give relief to patients who were experiencing seizures (attacks, fits) in their brains. Part of the task of giving relief necessitated a surgical removal of the some parts of the brain. Because they did not want to remove areas responsible for language functions, they had to first identify those areas responsible for speech. Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 355 It is in this phase of the brain research that identified and confirmed the fundamental areas where speech processing is carried out. They applied electrical stimulation to various areas in the brain which produced quite different reactions in the patients. For instance, when the electrical stimulation was applied to what is known as motor area, subjects experienced physical changes in the form of muscle contracting and trembling, or parts of their body lost sensitivity such as touching. This shows that the motor area is the centre of command to direct a person’s physical activities. As far as language is concerned, using vocal organs to speak gets instructions from the motor area. More importantly, perhaps, when electrical stimulation was applied to areas known as Broca’s and Wernicke’s areas, Penfield and LaMar engaged their subjects in speaking. The result was that their patients experienced either immense difficulty in speaking or produced cries that resembled language more than any other of sound. Once again for all, they established that Broca’s area, Wernicke’s area and the motor area were three major centers involved in speech processing and production. W. Penfield It is time now to examine what the paths / procedures are followed in the brain during the process speech is generated. Mechanics of Speech Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 356 The question of how speech comes to materialize is answered to a great extent by Geschwind (1972). According to Geschwind, speech occurs as a series of steps taking place in several parts of the left hemisphere. The type of steps can change depending on the stimulus that prompts a subject to speak. If the stimulus is a word that is heard, one particular series of steps are followed; if it is a written word, then another series of steps. If there is no verbal stimulus, yet another path is followed. In summary form, they are: Speaking without any verbal stimulus Speaking a word that is heard Speaking a word that is written Let us look at each of these in turn; first, speech without any verbal stimulus. Though no verbal stimulus exists here, stimuli can be either physical or psychological. Imagine someone who is hungry and wishes to say “I’m hungry.” There appear to be two basic phases: 1) Conceptualization, and 2) Speech. Conceptualization or the basic structure of utterance is generated in Wernicke’s area and straight after is sent to Broca’s area for the utterance to be encoded before it is forwarded to the motor area, which activates the vocal organs. SPEAKING WITHOUT ANY VERBAL STIMULUS Steps Step 1 Phases Conceptualization Features Utterance Generated Action Location Step 2 Step 3 Step 4 Speech Utterance decoded Readiness to Vocal organs speak activated Articulatory information Activated information Action taken to The word activated in passed onto speak spoken Wernicke’s area Broca’s area Motor area Actual Speech The second type of speech involves the repetition of word heard. When subjects are asked to listen to a word, the message is sent to the auditory area responsible for processing the incoming pronunciation. For the full processing to take place, the pronunciation is transmitted to Wernicke’s area as it is responsible for verbal language processing. Because the task is to repeat the same word, this Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 357 information (pronunciation) is passed onto Broca’s area for it to be conceptualized. The intention to repeat is converted into action when motor area receives it. Once the motor area instructs the vocal organs, speech occurs. SPEAKING A WORD HEARD Step 1 Phases Step 2 Step 3 Hear the word Action Location Step 4 Step 5 Speak the word Pronunciation Articulatory Activated Action The word received in information information taken to spoken activated in passed onto speak Wernicke’s area Broca’s area Motor area Auditory area Speech – Vocal organs The third type of speech in which a visual or written stimulus is involved. In other words, reading first and replicating the read word in speaking form. In the reading phase, written symbols are first received in the visual area, responsible for almost all the visual input into the brain. The area known as ‘angular gyrus’2 functions like a filter and sends it to Wernicke’s area for linguistic processing. Once the message/information in symbols is converted to language in this area, it is then forwarded to the Broca’s area. As for the speaking phase, it is in Broca’s area that abstract sounds symbols correspond to the written symbols are activated. Then the information is passed on the motor area responsible for controlling the bodily actions in the body. According to the instructions received from the motor area, vocal organs work together to produce the speech. SPEAKING A WORD READ Step 1 Phases Action 2 Step 2 Step 3 Step 4 Reading Step 5 Step 6 Speaking Written Written Written Same abstract Action is The word symbols symbols symbols symbols taken to spoken received in activated in decoded in activated in speak The pronunciation for it is / /. Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 Location Visual area Angular Wernicke’s gyrus area Broca’s area 358 Motor Speech – area Vocal organs Three most important areas emerge to be responsible for speech before it is emitted through the vocal organs: Wernicke’s Area → Center for Utterance Generation, Auditory Representation, Interpretation and Decoding Broca’s Area → Center for Encoding and Conceptualization Motor Area → Center for Command and Instructions Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 359 NLP: Neuro-Linguistic Programming In the two experiments described above, the stimuli for the subjects to speak were auditory (heard) and visual (written symbols), respectively. A person can normally be stimulated through his five senses: seeing, hearing, touching, smelling, and tasting. BRAIN’S FIVE SENSES Seeing Hearing Touching Smelling Tasting Visual Auditory Kinesthetic Olfactory Gustatory There have been attempts lately to utilize all or the preferred senses of people in all areas of learning and personal development. This is what NLP is about: identify the most or the more preferred channels (systems, senses) of language learners and design the syllabus according to neurolinguistic needs of the learners. Instead of relying heavily on visual or auditory techniques of teaching, teachers can vary their techniques and procedures by including activities based on kinesthetic, olfactory and gustatory. Basically, NLP teaches us two things: 1. Learners have different preferred systems of experiencing the world (knowledge, teaching, lesson, etc.), and 2. Learners may like to use, and so get stimulated to learn, various senses to learn more efficiently as they get involved in real-life like tasks. This will also modify a monotonous pattern of learning. Practitioners of NLP believe that if activities are designed in a way to tap different or the best functioning areas of brain, learning can be maximized. Conclusion No doubt, language is located in various locations in the left hemisphere with the right hemisphere contributing and perhaps complementing the tasks of the left. This, however, should not rule out the possibility of other areas having Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 360 meaningful contributions, though minimal. We can now safely say that the most important areas for speech are: Broca’s area, Wernicke’s area and the motor area. Knowledge of the relationship between language and brain will certainly benefit the language teacher, as we now know that various abilities are localized. Activating various areas in the brain through different activities for learners can help involve them in the learning process. Further, when devising activities in classroom, preferred ways of using the five senses can be identified and thus be implemented through the guidance of neuro-linguistic programming. Teaching through Neurolinguistics Knowledge Activity 1 References and Further Reading Fromkin, Victoria and Rodman, Robert (1983) An introduction to language. New York: Holt. Geschwind, N. (1972) Language and the brain. Scientific American, 226, 76-83. Harley, Trevor (2001) (2nd ed.) The psychology of language: From data to theory. East Sussex: Psychology Press. Lamb, Sydney M. (1999) Pathways of the brain: The neurocognitive basis of language. Amsterdam: John Benjamins. Penfield, Wilder and Roberts, LaMar (1959) Speech and brain mechanisms. Princeton: Princeton University Press. Wada, J. (1949) A new method for the determination of the side of cerebral speech dominance. Medical Biology, 14, 221-222. Neurolinguistics – Linguistics for Language Teaching, Çelik 2006 361