5 DnssoIutiiorBo language loss In many ways, this final chapter on the loss of language and the unworking of the mind is the obverse of Chapter i, which dealt with how babies acquire their mother tongue. But unfortunately, it is not just the natural progression of the years that can exact its toll on our speech. Dissolution can be caused by an unhappy accident which assaults the language area of our brain, or by a traumatic event in our personal life, or, as researchers are just beginning to discover, even by some unfortunate roll of the genetic dice. The study of abnormalities of speech has provided psycholinguists with several direct insights into the psychology of language, for example the slip of the tongue data reviewed in Chapter z. Another illustration of this type of inquiry is the large field of Second Language Acquisition (SLA) research, which could be considered a branch of applied psycholinguistics. Here, the errors that non-native speakers make while they are learning a new language have turned out to reveal at least some of the learning processes they employ. So it is no surprise that psycholinguists have found that the dissolution of language, whether due to accident or age, is a rich source of information about how the human mind controls our attempts to communicate. Neurolinguistics and language loss The evidence from aphasia We will begin with the most extensively studied examples of psy-cholinguistic dissolution, the loss of language due to brain damage. Since the brief comment on Emily Dickinson's poem quoted in Chapter i, talk about the brain has been avoided in an attempt to focus on the mind and on mental processes. So far we have assumed that mind and brain are relatively distinct and that it would be misleading to consider them psychologically synonymous. However a different perspective would take the other extreme and claim that the mind and brain are one. Neurolinguistics, an offspring of psycholinguistics, investigates how the human brain creates and processes speech and language. Before we examine the findings of neurolinguistic research, we need to clear up some popular misunderstandings about the human brain and the way it functions. One example is the disproportionate attention devoted to the well-known anatomical fact that human brains have two separate and virtually identical cerebral hemispheres. Biologically, this is an unremarkable piece of information, for this bifurcation is found in all vertebrates and is itself a characteristic of the bilateral symmetry that pervades our living world. However, there exists an unusual enchantment with the brain in our current culture, so that this anatomical condition has prompted a great deal of discussion about left brain versus right brain' differences in human behavior. What the media and most people forget is that, anatomically, there are millions of association pathways which connect the left and right hemispheres together so that in normal brains any information in either hemisphere is immediately shared with the other. The function of the corpus callosum (the largest sheath of association pathways connecting the two hemispheres) is often unknown, ignored, or misunderstood so that nowadays it is often represented as a 'fact' that there are 'left-brained' and 'right-brained' people in the same way that individuals can be left- or right-handed. Misconceptions like these about neurology lead, quite naturally, to misconceptions about the relationship between the brain and mental states or linguistic structures. But in this final chapter, it is time to take a look at the brain and to acknowledge "the legitimacy of neurolinguistics as a sub-field of the psycholinguistics of language. Sadly, we learn the most when this precious piece of anatomy is damaged. We can get an idea about the way the brain controls human speech and language without resorting to an anatomy text or arranging to view a craniotomy. Take your left hand and cup it over your left ear so that the palm of your hand is clapped over r your ear hole. You will find that your hand covers most of the left side of your head and that the first two fingers of your hand extend upward almost to the top of your scalp. If you could see the interior surface of your brain lying under your hand (as surgeons would if they had flapped open the left side of your skull to expose the brain in a craniotomy), you would be able to identify, after some scrutiny, two vertical strips of brain tissue running down from the top of your head, roughly the same size and in the same position as the first and second finger of your hand. The more forward strip, the one covered by your middle finger, is called the motor cortex and is the primary area of the brain for the initiation of all voluntary muscular movement. The strip just parallel to this, and covered by your index finger, is the sensory cortex. This is the primary location for processing all sensations to the brain from the body. Because our central interest is in language and not in the anatomical mapping of human neurology, we are most concerned with the location of the control of speech organs and the sensation of speech sounds within these two strips. And here, we run into one of the many oddities of our neurological system. It is, in fact, the top part of the brain which controls the lower extremity of the body and vice versa. In an equally counterintuitive manner, the left side of the brain is responsible for the right side of the body and vice versa. It follows that the tops of the motor and sensory cortices take care of the movement and sensation of your feet, and the bottom parts of these two strips are responsible for your head. Returning to the hand-on-the-head illustration, the tips of your first two fingers lie over the area of the brain which controls your feet (your right foot to be specific), and the base of those two fingers, where they meet your palm, cover the motor and sensory areas which control your head, mouth, and throat. Because language is represented for most people in the left hemisphere, the area of the brain which is crucial for the production and comprehension of human language is covered by the spot where your first two fingers join your hand. Because of their importance to linguistic communication, these two locations, motor and sensory, are named after the two nineteenth-century neurologists who first described their unique linguistic functions. The bottom portion of the motor cortex, the area that is slightly more forward and is covered by the base of your middle finger, is called Broca's area, named after a French physician, Paul Broca, who also helped coin the term aphasia, the loss of speech or language due to brain damage, jusr behind this area, at the lower portion of the sensory cortex, the spot covered by the base of your index finger, is Wernicke's area, named after Broca's Austrian contemporary, Karl Wernicke. These discoveries of the location of speech centers in the cerebral cortex well over a century ago also helped to demonstrate that the human brain differs from the brains of most other animals because it was not equipotenttal. For many species, including mammals like rats, much of the brain seems to function holistically; if half a brain is damaged, the animal seems to lose about half of its functions, so approximately any area is equal in [ potential importance to any other area. Not so with the human brain, as Broca, Wernicke, and other nineteenth-century neurologists discovered and as has been further confirmed and refined by a century of research. One of the first pieces of evidence that certain functions of human behavior were localized and were not diffusely represented throughout the brain was this nineteenth-century discovery that different areas of the brain controlled different language functions. Speech production resided largely in Broca's area and comprehension of language was confined pretty much to Wernicke's area. By localizing specific functions to particular areas, it seems that human brains create more compact and powerful neurological 'computers' than those employed by most other animals, which tend to rely more on the equal potential of any area of their cortex for functional processing. But like all animals, humans are susceptible to injury, probably even more susceptible than animals when it comes to the central nervous system (the brain and spinal cord). Suppose a friend or • relative of yours was unfortunate enough to sustain an injury that just happened to be located in either of these two relatively small areas of the brain straddling the top of your left ear. The damage could arise from a loss of blood supply to that location due to a stroke, or from an invasive injury like an automobile accident or a gunshot wound. There are at least two consequences to misfortunes like these that make the central nervous system unique in relation to any other part of the body. First of all, because there are no pain receptors in the brain, any distress that is felt comes from the tissues that surround the brain, the source of discomfort in a headache, and not the brain itself, and that is why a stroke, unlike a heart attack, is not necessarily a painful experience. The second irony is that of all the tissue that comprises the human body, the nerves in the central nervous system do not regenerate. Once they are damaged, they do not grow back, so brain injury is permanent, though, given the right circumstances, functional loss is sometimes recovered, most frequently within a year of the initial injury. Let us return now to the consequences of injuries to the two 'language centers' of the brain. There are many different types of aphasia, varying in their degree of severity and the way they might overlap, but the two classic types are representative of this malady. Damage to Broca's area usually affects one or all of the stages of speech production reviewed in Chapter 2. Broca's aphasia is characterized by speech and writing which is slow, very hesitant, and in severe cases, completely inhibited. Although automatic speech and function words can remain almost unaffected, usually the production of key words, like subjects, verbs, and objects, is hesitant and inaccurate. Nevertheless, comprehen-sion is relatively spared. If the injury is located in a more posterior position, just to the back of the upper ear, then patients usually experience Wernicke's aphasia; speech production and writing are pretty much intact, but because the sensory cortex is damaged, patients experience a great deal of trouble processing linguistic input. Although speech flows more fluently and comfortably than for Broca's aphasics, patients afflicted with Wernicke's aphasia tend to ramble somewhat incoherently. Part of this steins from their inability to process conversational feedback due to the problems they confront in comprehension. Remember that in both types and for most cases, aphasia occurs only if either of these two areas are damaged in the left hemisphere of the brain. Broca's and Wernicke's areas are unilateral, and reside only in the left hemisphere, at least for almost all right-handed people. Damage to the parallel areas in the right hemisphere does not normally affect in language production or comprehension, although, as neuropsychologists have discovered, it affects other types of human behavior, for example the correct recall and naming of familiar faces, or the ability to read maps. A good illustration of the type of language dissolution these two types of aphasia create is found in the following excerpts from speech produced by a Broca's and a Wernicke's patient. Although written transcripts fail to capture many of the features of speech so conspicuous in a tape recording or face-to-face interview, the examples printed below reveal remarkably different patterns of linguistic production for the two patients. The Broca's aphasic struggles to search for appropriate words and ends up producing mostly nouns. He also seems unable to use grammatical function words to string phrases and clauses together, although his intention to communicate is almost painfully apparent. The speech of the Wernicke's patient, on the other hand, appears to be a series of cohesive phrases and clauses, without coherence or apparent communicative purpose. Broca's aphasia [The patient is attempting to describe an appointment for dental surgery.] Yes... ah ... Monday... er ... Dad and Peter Hand Dad ... er... hospital... and ah ...Wednesday ...Wednesday, nine o'clock ... and oh ...Thursday ... ten o'clock, ah doctors... two ... an' doctors ... and er... teeth ... yah Wernicke's aphasia [The patient is trying to describe a picture of a family in a kitchen.] Well this is... mother is away here working her work out o'here to get her better but when she's looking, the two boys looking in the other part. One their small tile into her time here. She's working another time because she's getting too ... • (from H. Goodglass and N. Geschwind. 1976. 'Language disorders (aphasia)' in E. C. Carterette and M. P. Friedman (eds.): Handbook of Perception: Volume 7. Language and Speech. Academic Press, pages 3 89-42.8) -J * L'Tinurv T The surgical evidence Neurolinguistics has progressed enormously since the nineteenth century, and as a consequence of advances in diagnosis and surgery, the particular sub-field known as aphasiology {the study of aphasia, or loss of speech) has flourished especially. Two kinds of surgical operation have a particular bearing on questions of language dissolution. One of these procedures is hemispherectomy. In rare cases, when a life-threatening neurological condition is found in either the left or right hemisphere of a patient (for example a rapidly growing malignant tumor), and there is no alternative to surgical treatment, neurosurgeons will open up the affected side of the skull and remove almost the entire left or right hemisphere! This procedure used to be performed even on adults, but now it is fairly much restricted to children under the age of ten. There is a dramatic difference between the effects of this operation on adults and young children when it comes to speech. When an adult undergoes a left hemispherectomy, he or she becomes completely aphasic, except for a few words of automatic speech, and this is why such operations are rarely performed nowadays. Conversely, hemispherectomies performed on young children, quite amazingly, do not lead to loss of speech. How do we reconcile this neurolinguistic phenomenon with the claims made earlier that language centers are localized to specific areas of the left hemisphere? Certainly, the key factor here is the age of the brain. During the first decade of life, the human brain is continuously evolving and growing. Cognitive and linguistic functions have not yet been localized to specific areas (although these sites appear to be genetically predetermined), and this allows for the neuroplasticity of the still maturing brain. When a young brain encounters traumatic injury, even to the extent of losing an entire cerebral hemisphere, because it is still maturing, and because the primary areas of cognitive and linguistic functioning have not undergone canalization (established as neuronal networks), a child does not suffer the extensive functional loss that an adult does. Consequently, we can see that the effects of neurological damage on linguistic performance are not strictly predictable from anatomical change. In this case, for example, age is a critical factor. Does this mean that children are spared all neuropsychological or neurolinguistic disadvantage? Certainly not. Childhood aphasia exists, though it is much less common than its adult counterpart, and congenital language disorders such as autism, to be discussed in a moment, very likely stem from neurological abnormalities. But we can see even after this briefest of excursions into neurolinguistics that it is difficult to forge clear-cut links between the neurology of the brain and the language of the mind. A second, and better known, surgical procedure which also has neurolinguistic relevance is the split-brain operation which was developed in the 1970s to help treat specific and rare cases of severe epilepsy. This ancient affliction is most often caused by discharges in the motor cortex in one hemisphere that are instantly transmitted to the corresponding cortex of the other hemisphere via the corpus cailosum. There are certain severe and singular forms of epilepsy which remain unaffected by pharmacological treatment, and split-brain surgery was developed to spare sufferers from the terrible trauma of major seizures. In an operation much less dramatic than a hemispherectomy, the surgeon makes a front-to-back incision along the corpus cailosum, severing most of the association pathways which connect the left and right hemisphere. Although this might sound almost as grim as a hemispherectomy, there are actually very few negative consequences to the operation, and this rests largely on the fact that all of our senses are bilaterally represented. Our left eye, for example, is controlled by both hemispheres: the left visual field (everything we see to the left of center) is controlled by the right hemisphere and the right field (everything we see to the right of center) by the left hemisphere. The same is true for the right eye, and so even after the corpus cailosum is cut, in normal, everyday situations, information from either eye goes to both hemispheres. A number of unique neurolinguistic consequences of this surgical operation have been discovered. Most daily functions, including speech and language were found to be unaffected; it was only under experimental conditions that certain strange, linguistic processing constraints emerged. For example, when specially selected words were flashed very rapidly on a screen, normal subjects read them as single words, but these same words were read as only half a word by the split-brain patients. Take the following illustration. When the word 'HEART' was flashed to subjects on a r screen, with the middle of the word right in the center of the field of vision, normal subjects had no trouble in reading it. When the same word was flashed to split-brain subjects, however, they read only the right half; rhat is, they claimed they saw just the word 'ART1, and seemed to miss completely the 'HE1 on the left. HEART HEART [What normal subjects read.] [What split-brain patients read.] The discrepancy can be explained by the fact that when a word like 'HEART' is flashed momentarily in front of our eyes, the image does not last long enough for us to read it completely, but we can reconstruct it as one word because our corpus callosum instantly transfers all linguistic information which enters our right hemisphere from the left visual field into our left hemisphere, the one that contains the language centers which comprehend and produce language. These centers immediately read this linguistic stimulus as one word, 'HEART'. Under non-experimental conditions, when there is much more than the merest fraction of a second to catch a word, a split-brain patient has time to scan back and forth and ensure that both the right and the left side of the word are caught by the right visual field and hence fed directly to the left or linguistic hemisphere. The word is then read correctly, just as it was by the patient before surgery. But under these experimental conditions, when words are flashed too fleetingly to be scanned, the split-brain patient is confined to reading only half the field of vision, always the right half. Since 'ART' is an English word, and since it is quickly fed from the right visual field directly to the left hemisphere, it is the only word that is comprehended. Because it lies in the left visual field, 'HE' is just as quickly picked up by the right hemisphere, but since the neurological bridge between the two hemispheres has been cut, the lexical information remains trapped in the right hemisphere, which is not as literate as its cerebral twin. But the left side of the brain does not monopolize all of language processing; there are secondary or tertiary linguistic areas even in the right hemisphere, so split-brain patients are dimly aware that there is more than just the word 'ART' staring them in the face. When they are asked, however, to point with their left hand to the word they have just read ('ART'), patients usually point to the letters 'HE'. Apparently, they are influenced by the stranded memory of the word, 'HE' that is floating in the periphery of consciousness in the right hemisphere. What do the split brain studies tell us about neurolinguistic processing? Some of them have been interpreted to the public as support for the left versus right brain duality. They have been viewed as additional evidence that the left brain houses the logical and conscious mind whereas the right brain is home to the intuitive and the unconscious. But it is not very useful to draw such gross generalizations about normal neuropsychological processing from the results of split-brain patients in experimental studies. It is an enormous leap of faith and logic to assume that the inability of patients to fully process a word flashed momentarily on a screen because their corpus callosum has been severed due to severe epilepsy can be generalized to the claim that, in normal people in everyday situations, the right hemisphere is the seat of intuitive, nonconscious thinking. Research into aphasia, and studies of hemispherectomy and split-brain patients, has given rise to two superficially contradictory claims about the manner in which the brain processes language. On the one hand, there is irrefutable evidence that for the vast majority of adults, the production and comprehension of speech is located in two closely situated but clearly distinct areas of the left hemisphere, Broca's and Wernicke's, and this localization of function is not fully completed until about ten years old. An incidental corollary of this fact is that the exceptions, who number from five to ten percent of any given population, tend to be left-handers. For them, there is a greater probability of language being localized to the right hemisphere or being represented bilaterally. On the other hand, in contrast to these claims •about the neurolinguistic primacy of the left hemisphere, research in all areas of language dissolution shows that human linguistic ability does not solely reside in these two relatively small areas on one side of the brain. The left-handed exceptions just cited are a singular counter-example. But even for the preponderance of people, who are right-handed, more and more evidence has implicated the role of secondary and even tertiary areas of speech T processing. The 'HEART' example described above provides support for this. These two findings alone are enough to call into question the validity of neuropsychological models which neatly map various human behaviors on to the brain like a modern version of phrenology, the belief, popular in the nineteenth century, that the configurations of the skull's surface indicated the presence of different emotions. They suggest, instead, that models which use the analogy of a hologram might be more representative of how the human brain works. Holography is a modern form of photography which uses lasers to mold thousands of holograms together to create a rough, but identifiable, three-dimensional picture of an object. Each hologram, or individual cell, in that picture has the potential to depict the entire picture. In other words, holography creates a single picture from many individual depictions of the original. Genuine 'neurolinguistic programming' seems to work in the same way. There are primary locations in the brain for all complex human activities such as language; nevertheless, at the same time, language is diffusely represented in several other locations as well. The holographic metaphor also helps explain why neuroplasticity is lost. The different areas of the young brain can be neurologically programmed to fulfill a variety of functions, but as the child's environment and experience grow in complexity, these various functions are localized to allow for a more efficient allocation of neurological tissue. At about the onset of puberty, as the child enters an adult world, neuroplasticity is lost because localization is complete. But, like the hologram which is both one picture and many, the overall control of language and speech is both localized and diffuse. Speech and language disorders Dissolution from non-damaged brains Up to this point, we have been discussing examples of language dissolution that are the result of operations on the brain, but these cases are rare when compared to the many ways in which an individual's language can deviate significantly from social norms. Their number is too vast to summarize adequately here, but a brief review of two representative examples, stuttering and autism, will help to reinforce several themes and insights that have been brought out earlier in this book. Stuttering, also referred to as stammering, is one of the most common articulation problems encountered by speech pathologists, at least in most English-speaking countries. Like the slips of the tongue reviewed in Chapter 3, stuttering reveals psycho-linguistic information about how speech is organized and planned. Research has demonstrated, first of all, that stuttering is not random: it does not punctuate our speaking spasmodically, tike a hiccough. It occurs, most frequently on the initial word of a clause, the first syllable of a word, the initial consonant of a syllable, and on stop consonants (like /p/, /t/, /[