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Extract from The Bilingual Brain
By Arturo Hernandez
Chapter 1 Antagonists, Parasites, and Symbiotes
It was at the age of 20 that I first
encountered the paradox that would come to dominate my academic life and that serves as the major impetus for this book. I was taking a class in cognitive neuropsychology at the University of California, Berkeley, with Art Shimamura, a newly minted assistant professor, who had moved up the coast from La Jolla after a postdoc with Larry Squire. During class we learned about patients who had suffered strokes and lost the ability to do things that most people take for granted. Some lost the ability to remember new things (amnesia), some lost the ability to focus on things on the left side of space (spatial neglect), and others lost the ability to use language (aphasia).But the class unit on language actually began with a discussion of presurgical mapping. The pioneering work by Wilder Penfield in the 1930s (Penfield & Boldrey, 1937) had been extended by George Ojemann, a neurosurgeon at the University of Washington Medical School. In this work neurosurgeons stimulate the brain directly in order to map out the language zones. Based on this literature, Kolb and Whishaw (1985) suggested that individual variability in the size of the language zones was most likely due to how well a person used the language.
Two facts supported this view. First, females had smaller language zones than males, a likely reflection of their superior verbal skills according to the authors at the time. They suggested that less ability in a language results in a more diffuse brain representation, which “is supported by his [Ojemann’s] observation that in multilinguals the poorer language is disrupted over a larger area than the better one” (Kolb & Whishaw, 1985, pp. 570–571). In short, there seemed to be a relationship between how focally a language is represented in the brain and how well it is spoken. Surprisingly, the entire chapter we read on language contained no additional reference to the neural representation of bilingualism or multilingualism.
My curiosity piqued by this topic, I made an appointment to see my professor. Art Shimamura was personable and approachable and he patiently sat with me as I asked him about bilinguals. He pointed me to the work of Ojemann that had been mentioned in the class textbook (Ojemann & Whitaker, 1978). I quickly went to the library and looked the article up only to find that the two cases presented showed a very different profile. There was no place in the brain for each language. Furthermore, the patients had very different language profiles. One was a late bilingual, whereas the other was an early bilingual.
Intrigued by this topic, I spent time in the library hunting through the aphasia literature looking for cases of bilinguals who had lost the ability to use one of their languages after some form of brain damage. I asked a teaching assistant, Felicia Gershberg, whether she thought it would be appropriate to do my final paper on bilingual aphasia. She said yes. Luck would have it that there was a special issue of Brain and Languagededicated to this topic.
As I read through the different articles, I stumbled across a case that caught my attention. A.S. was a 49-year-old experienced orthopedic surgeon who spoke Farsi as a native language but went to college in Germany at age 18. During this time, he also spent a year doing research in England. Although Farsi was his native language, the patient also spoke German and English, his second and third languages.
On September 2, 1985, at the age of 49, A.S. was injured by an explosion that led to left frontotemporal trauma. He lost consciousness temporarily and was hospitalized that same day. After regaining consciousness he could say a few words in Farsi for the first 16 days before he switched to German. Much to everyone’s surprise, he could understand both Farsi and German, but could only speak in German even to monolingual Farsi speakers for the next 3 weeks, after which he switched back to Farsi. As he alternated between German and Farsi during these first few weeks, he was unable to speak or understand English. He regained the use of English only after having completely recovered his mastery of both Farsi and German.
Why did this particular case study capture my interest? Just two years earlier, I had experienced a similar episode during my first few months in Brazil, where I was immersed for the first time in Portuguese, my third language. In a brief period of time, speaking Spanish, my mother tongue, became extremely difficult and labored. In addition, English, my dominant language, was quickly becoming less and less accessible. I found it very difficult to write, read, or speak it with the fluency I had possessed just six months earlier.
Over two years, I became so proficient in Portuguese that people mistook me for a native. But my newfound proficiency in Portuguese came with a cost. My return from Brazil was marked with a couple of semesters of agony as I slogged through textbooks that used to be a breeze. And my Spanish, which had been native-like, now sounded strange to my grandmother.
At the age of 20, like patient A.S., I had suffered my own alternating antagonism, during which increased accessibility in one language was accompanied by loss in another language. But this interference between languages was not due to brain damage. It was simply the product of being immersed in a third language.
Cases of language loss and recovery bring up an intriguing paradox. If two languages are stored in the brain, how can it be that a person could lose a language and gain it back? My own experience and the cases of bilingualism that I was reading at the time suggested a very different model of how a language was represented in the brain. It appeared that languages could be inaccessible even though they were not entirely lost. Hence, stress, whether it be due to foreign language immersion, sleep deprivation, or brain damage, could lead to the apparent loss of one language and not the other. In my case, even though Spanish was my mother tongue, it was a language that I had used to a much lesser extent. English was my most literate language and as such it withstood the onslaught of Portuguese immersion much better.
This episode also showed me that the brain was not egalitarian. Rather than giving similar representational privileges to all languages, it favored some languages over others. And so I set off on a quest to understand the factors that might help to predict how two languages are coded in one brain. This book fleshes out this topic with results that have come out in the 22 years since I first stumbled on this field of study as an undergraduate at the University of California, Berkeley. In this time researchers spanning the globe have generated a lot of new information. However, interestingly a lot of this information builds on existing notions that were introduced many years ago.
Familiarity and Its Neural Instantiation
The phenomenon of alternating between languages shown by patient A.S. (and by me) shares the flavor of the conclusion that Kolb and Whishaw suggested in the third edition of their classic textbook. Stronger languages are more efficient and hence may be most resistant to brain damage. The weaker language may be more spread out across the cortex and hence may be less resistant to damage.
The idea that stronger languages might be more resistant to damage was also present in early work carried about by Pitres in 1895. Jean-Albert Pitres was born in Bordeaux in 1848 (Lebrun, 1995). He studied medicine in his birthplace before joining the army and serving as an auxiliary physician in Paris. He completed his studies in Paris and went on to work with Charles Emile Francois-Frank (1849–1921). Upon completing his training he returned to Bordeaux, where he took a position in the newly formed school of medicine.
Pitres noted that selective impairment of a language in a patient who was bilingual or multilingual was quite common. He then went on to review a number of cases in which he describes the loss of language in multilingual aphasics. Some patients retain access to only one language. For example, consider the case of a 56-year-old male who lived in France but learned German as a child and Basque, English, Spanish, and Italian as an adult. After a suspected stroke during which he lost consciousness, he had difficulty moving the right side of his body, what neurologists would call right-sided hemiplegia. Over time he recovered his ability to use French but not his other five languages. Although other cases reviewed by Pitres showed recovery in several languages, there was always a differential amount of recovery of some languages relative to others.
Based on these cases, Pitres formulated the generalization that the strongest language would remain resistant to damage. This is known as Pitres’s rule. In addition, Pitres noted that many cases showed temporary “inertia” and that once this was overcome there was no need to think that aphasics were growing new language centers for each language.
The idea that familiarity of language is important for the recovery of language has played an important role in the child and adult bilingual literature. Language proficiency, as it has been termed today, has been found to play a central role in the neural representation of bilingualism (Abutalebi, Cappa, & Perani, 2001; Chauncey, Midgley, Grainger, van Heuven, & Holcomb, 2004; Chee, Hon, Lee, & Soon, 2001; Elston-Guettler, Paulmann, & Kotz, 2005; Mechelli et al., 2004; Meschyan & Hernandez, 2006; Perani et al., 1998; van Heuven, Dijkstra, & Grainger, 1998; Xue, Dong, Jin, Zhang, & Wang, 2004) and in the behavioral responses seen in the cognitive literature (Birdsong, 2006; Costa, Santesteban, & Ivanova, 2006; Kotz & Elston-Guettler, 2004). To this day, the idea that stronger languages are represented differently than weaker languages remains.
Age of Acquisition
In addition to language proficiency, the age at which a language was learned, age of acquisition (AoA) can also be seen as playing a role in the recovery of function observed with patient A.S. The alternating antagonism he experienced was between German and Farsi, his first and second language. The third language, English, took the longest to recover. This case suggests that when a language is learned may also play a role in its speed of recovery. This can be seen in some case studies. The question remains whether other cases show the importance of AoA in their recovery.
Other cases show a similar resistance to damage of earlier languages (Bianchi, 1886). There is the case of A.A., a healthy 24-year-old man, short and muscular but well proportioned. He was an excellent businessperson working successfully as a traveling salesman abroad. Aside from Italian, his native language, he also spoke French and English, which he had learned early in life. One day following an episode of extreme convulsions he was promptly taken to the doctor for treatment. Like A.S., A.A. suffered from hemiplegia, difficulty moving half his body, and had difficulty producing any speech. Upon examination it became clear that he could say some words in Italian but did not understand the link between these words and the corresponding objects in the real world. However, over time, the link between a word and its real-world referent became stronger. Unlike A.S., A.A. was never able to fully recover all the languages he spoke. Whereas he showed a considerable amount of recovery in Italian, he was never able to say a single word in French or English again. In the case of A.A., the first language was the last one left standing.
On the surface, the case of A.A. supports Pitres’s rule, since Italian, the most familiar language, is preserved relative to the other two. But in this case, familiarity is confounded with AoA, since Italian was also the patient’s first language. A.A. learned both French and English early and spoke both of them very well before the damage. However, they were learned after the first language was already in place. This would suggest that the first language might have some strength over and above pure familiarity. At least in this case, we would have to accept that AoA may not just be familiarity in disguise.
The notion that age of learning was a principal driving force in recovery of language for bilingual aphasics predates Pitres. Ribot, considered by many to be the father of French psychology, had proposed that language representation in bilinguals would be driven by when a language was learned (Lorch, 2009; Ribot, 1881,1882). He saw this as a natural extension of the general laws that ruled the organization of memory. He noted that when patients had difficulties with word finding they would show the same order of loss: proper names, common nouns, adjectives and verbs, interjections, and finally gestures.
In each of these categories, patients would forget their most recent memories first and their earliest memories last. This regression would proceed from items that were new, complex, voluntary, and least organized to items that were old, simple, automatic, and best organized. In short, Ribot proposed the idea that “age of acquisition” played a profound role in the formation of memories.
Ribot also proposed an interesting view on what today would be termed automaticity. He noted that there are very simple organic or motor memories, which are deeply engrained and not available to consciousness. This is what many today would term procedural memory (Squire & Zola, 1996). In addition, there are conscious memories that are formed over time. As we encounter a number of events across time, the time stamps associated with individual instances are lost.
This would naturally lead to the loss of specifics for a particular episode and the retention of commonalities across memories. In short, these new conscious memories would take on the form of organic memories in that they would be deeply engrained. Furthermore, these new memories would involve the characteristics that were common across all the different episodes.
At the time that Ribot was developing his theories, there was little in the way of theoretical or empirical psychological work with children. However, there was an existing literature on second language acquisition that built on then-current ideas that distinguished between speech (motoric memory) and comprehension, which was considered a component of the mind. In fact, Ribot was hinting at the distinction between speech and other forms of memory. As we will see in this book, AoA seems to have effects on certain types of language functions, especially those related to speech. However, other components of the mind seem to be less influenced by AoA to a certain extent.
Finally, Ribot considers the case of the recovery of lost languages in multilinguals. Of particular interest to him were patients who under anesthesia showed amazing recovery of a language even after protracted periods of little use. One example that he uses is the case from Duval’s article on hypnotism.
An old forester had grown up on the border with Poland, where he only spoke Polish. Afterward he lived in the German districts, and his children verified that for more than thirty years he neither heard nor spoke a single Polish word. However, upon being administered anesthesia he spent close to two hours, speaking, praying, and singing, exclusively in Polish (Ribot 1881, 1882, p. 181).
The forester had these memories even though he had used German exclusively during his adult life. The deeply engrained memories were released as soon as the conscious mind was put to sleep. Hence, even though new memories can become very well engrained during an adult’s life, the primary memories will remain over time when the conscious mind is put to sleep. The fact that the second language is built using the conscious mind and the first language is built using organic and motor memories is the basis for Ribot’s claim that AoA plays a crucial role in the neural representation of both languages in a bilingual.
Beyond Language: The Role of Control
Whereas Pitres and Ribot proposed the two mechanisms of AoA and familiarity/proficiency as playing a crucial role in the neural instantiation of two languages, there still exists the possibility that impairment may not have to do with damage to the cortex that is involved directly in language. Rather, the impairment may involve mechanisms that are involved in helping to select or switch to the correct language. Loss in the ability to switch from or to a language would result in the apparent loss of that language. However, it would not be loss per se but rather loss in the ability to control which language is available.
The first to propose the idea of a switching mechanism was Otto Pötzl, an Austrian neurologist born in 1877 in Vienna, Austria, where he completed his medical training. He is best known for his work during his tenure at the Vienna Psychiatric and Neurological Clinic, where he joined Freud’s psychoanalytic movement and became one of its most ardent supporters. But our story takes us back to 1922, when he took a position as head of psychiatry in Prague (Pötzl, 1983). During this time he encountered a bilingual patient who had a strange syndrome.
The patient was a 60-year-old Austrian businessman, a native speaker of Czech, who had learned German at 14. As an adult he had moved to Vienna and used German exclusively in his family and daily life. The patient suffered two strokes that had caused him to lose the ability to see the space that was directly to his right. Furthermore, he suffered from a peculiar language impairment. He could understand both Czech and German but he could only speak Czech. A subsequent patient with a very similar problem led Pötzl to conclude that some bilinguals suffered from a problem with language fixation. Although they understood both languages perfectly, they remained fixated on the language they had used during their first few days after the stroke.
In 2000 Franco Fabbro (2000), one of the premier experts in the neurolinguistics of bilingualism, encountered a similarly odd case. A 56-year old Friulian man, patient S.I., was a prominent land surveyor who learned Friulian as a native language but was educated in Italian for 13 years. Although close to a million people speak this dialect in the northeast portion of Italy, the vast majority also speak Italian, the majority language. During a vacation with an Italian monolingual friend, the patient noticed that he began to intersperse Friulian sentences with his Italian friend. He kept apologizing and translating for his friend. But it was quite unnerving. Later he began to notice problems moving the right side of his body and eventually found walking more and more difficult.
The patient met with Fabbro and it was quickly determined that he had a tumor, which was resected. After the tumor had been removed, the patient presented with a very odd pattern of communication whereby he would alternate between his two languages across sentences. He never mixed languages within a sentence. But the patient would consistently say one sentence in Friulian and one in Italian even when he knew the person listening spoke only Italian. When tested with a set of standardized neuropsychological instruments, he showed no real language deficits. He understood each language very well. He could repeat words in each language almost perfectly. He could even translate between his languages. The problem seemed to be restricted to spontaneous speech.
The two cases presented by Pötzl and Fabbro provide us with an intriguing insight. These two individuals understand both languages very well. Hence, these two syndromes do not involve language loss. Rather it is a problem with the ability to access each language. Researchers have come to think of this as a problem with language switching.
The metaphor of a language switch, originally proposed by Wilder Penfield in the 1950s (Penfield & Roberts, 1959), has gained popularity in the literature in recent years. The idea is that bilinguals have to use general control mechanisms in order to access each of their two languages at the appropriate time. However, the importance of control has also been explored in bilinguals relative to monolinguals. These findings suggest certain advantages for bilinguals on tasks that, at least on the surface, have nothing to do with language.
The three themes that arise from the bilingual aphasia literature, AoA, proficiency, and cognitive control, serve as the main guiding posts in the present book. Hence, this book is divided into three main sections.
The first section, which consists of two chapters, expands on the role of AoA in determining the nature of the bilingual mind. Chapter 2 presents a model for understanding how language and mind develop. For centuries, philosophers, theoreticians, and researchers have debated two opposing viewpoints on how humans acquire knowledge—nature versus nurture. Is knowledge innate or learned? I consider the issue of language and cognitive development in light of this question. A review of the literature quickly leads us to realize that certain things are learned earlier than others. Also discussed is recent work that suggests a different metaphor for language learning.
In this view, early language learning may actually build itself using basic sound elements of language. The ability to make fine phonological distinctions even for sounds from an unspoken language is present very early in life. In addition, young children spend hundreds of hours focusing on the spoken form of language. This emergentist approach in which larger skills—like language—are built from the bottom up provides the overarching themes that are explored further in the second chapter of this section.
In chapter 3, we expand this view to consider how age affects language learning in bilinguals. We begin by considering the nature of language learning in bilingual children. One of the central questions in the literature is whether bilinguals use one system or two. Initially, some researchers have suggested that bilingual children start off with a single integrated system that later develops into two. However, researchers have found that children can differentiate both languages very early in life.
In addition, there appears to be considerable flexibility in the system. Skills appear to transfer fluidly from one language to another. Results from these studies add further support for the emergentist notion that was proposed in chapter 2. Specifically, bilingual children build up two language systems from the start. This creates a different neural representation than that seen in adult learners of a second language.
The second section of the book considers the role of proficiency in the neural and cognitive processing in bilinguals. This is covered in two separate chapters.
In chapter 4, we consider the nature of proficiency, starting with the wider issue of expertise. Expertise exists across many domains. This is best exemplified in the work of Anders Erikson, who has found a set of general principles that apply across domains. Specifically, expertise is built up across time through deliberate practice in which individuals seek out or receive specific feedback about what is correct or not. This is thought to occur across many nonlinguistic domains. For example, recent work suggests that adults show similar types of acquisition profiles for nonfaces as those exhibited by children for faces (Gauthier & Nelson, 2001).
This view is also mirrored in the monolingual literature, where adults and children are seen as utilizing similar skill acquisition systems (M. H. Johnson & Munakata, 2005). In its essence this view suggests that practice leads to changes in proficiency or expertise that are specific to language.
Chapter 5 considers the neural bases of language proficiency, focusing on bilinguals. Recent work on language proficiency has begun to identify the neural underpinning of improved skill. In general, experts tend to show smaller foci of activity relative to nonexperts. Most importantly, language proficiency seems to affect certain types of functions more than others. Language functions that involve the processing of meaning are more highly affected by language proficiency. Others, however, are less likely to be affected as strongly by language proficiency. For example, accent is much less likely to improve past a certain point even with continued increases in vocabulary and other higher-level forms of language in second language learners. Hence, proficiency has a bigger impact on certain language forms than on others.
The third section of the book moves beyond the AoA/proficiency factors that dictate the neural representation of language and considers the role of cognitive control in language processing. As noted earlier, researchers have used the metaphor of a language switch to explain a third type of deficit in which patients exhibit an inability to control which language is being spoken. The two chapters in this section shed light on current research in this area.
Chapter 6 addresses the nature of control in the context of monolinguals. I discuss how control develops across childhood and eventually declines in older adulthood. I also discuss how control plays a central role in task- or set-shifting. Chapter 7 expands on the nature of control within the bilingual context. Both Pitres and Ribot alluded to the fact that language loss could reflect temporary difficulties that were not directly due to damage to the language cortex. Pötzl took it one step further by suggesting that some regions of the brain were specialized for controlling access to one or the other language.
The notion of a switching mechanism within the brain had already been proposed by Penfield, who suggested that bilinguals might employ a switch that could be used to maintain access to each language. In the 1960s and 1970s, a series of studies on language switching were conducted, with mixed results. The studies often explored whether there was a cost to switching and under what conditions this cost appeared. This increased cost could be in the form of absolute reaction time or in reduced ability to process the meaning of words in mixed language conditions.
In the late 1990s the field turned to brain imaging techniques in order to uncover how the brain handles language switching. During the first decade of the 21st century, fMRI (functional Magnetic Resonance Imaging: Editor’s note) research led to one clear finding. The brain areas involved in language switching do not appear to be specific to language. Rather it appears that the bilingual brain uses areas involved in cognitive control when switching between languages. Finally, there is evidence that these control mechanisms may also get recruited in a less proficient second language. This suggests that bilinguals may be using more cognitive control in their everyday lives.
The importance of control also appears to have unintended benefits. Early research found that bilingual children showed better flexibility. For example, they understood that the sun (e.g., the object) was not the same as the word “sun” at an earlier age than monolingual children. This early ability to distinguish a word from its concept is due to the fact that bilinguals learn very early that there is more than one word for the same thing. Pioneering work by Ellen Bialystok found that this flexibility in the language system extended to tasks that require attentional flexibility. Furthermore, recent work suggests that bilinguals are able to modulate control on nonlinguistic attentional tasks. This bilingual advantage is most likely to appear in a person’s 30s or 40s but is much more visible after age 60.
Chapter 8, the final chapter, brings these three strands together into a more coherent whole. In the first section, we considered the role of AoA in language learning. What emerges from the developmental literature is a clear view of how the brain is built up in expanding and overlapping systems. The earliest systems are devoted to sensorimotor processing. As development proceeds, later developing brain areas (e.g., the prefrontal cortex) become devoted to more complex processing. However, adults come to the language learning environment with a fully developed system. The use of these higher order systems provides certain advantages when learning explicit rules. However, this specialization naturally impedes the use of sensorimotor processing in later learned languages.
In the second section, we considered the role of proficiency. Proficiency is interesting because it builds over time and is the result of intense practice. In the bilingual domain, proficiency has come to be associated with higher-level cognition, which appears in the processing of semantic violations and in certain higher-level grammatical forms. Finally, the third section builds on these earlier two sections by considering the role of cognitive control. There is clear evidence that the brain areas involved in language switching are involved in many other cognitive control tasks.
Newer work suggests that bilinguals may show advantages when performing tasks that require cognitive control. This link is particularly interesting in the elderly, who exhibit larger language switching effects relative to young bilinguals but show significantly larger advantages relative to monolinguals on nonlinguistic control tasks. These results point to a link between cognitive control and language processing. In short, the neural bases of bilingualism are defined by AoA, language proficiency, and cognitive control. All three factors work together across time.
The book begins with a paradox. There are cases of patients who lose a language that seemingly lead us to think that bilinguals have separate areas for each language. The reality is much more complex than that. The reason for this complexity has to do with the nature of language itself. What researchers have come to call language is actually a collection of things that develop over a protracted period of time.
This collection of things is affected by three different factors. AoA affects the order in which these things are put together. If two languages were assembled in slightly different ways, then they might actually break apart differently. In addition to this there is the component of expertise in a language that develops over time. This expertise is due to the amount of use over time. And finally, there are different control components that come into play that may affect one language and not the other.
To date many researchers have suggested different types of models. Some have suggested an information processing approach, in which bilingualism is conceptualized as a set of mental programs. Others have suggested a more localizationalist approach, in which different languages are placed in specific areas of the brain. Others have taken a more linguistic approach, in which they describe the structure of each language and how it breaks apart after brain damage.
These different approaches are all rooted in different disciplines and emphasize different aspects of language processing. Whereas each of these serves as a framework for certain aspects of the field, they have fallen short in attempting to provide a framework for understanding the neural bases of bilingualism.
What I propose in this book is to extend recent work that has begun to take a biological or natural systems approach. In short, I propose that two languages live inside one brain almost as two species live in an ecosystem. For the most part they peacefully coexist and often share resources. But they also compete for resources especially when under stress, as occurs when there is brain damage.
Finally, the nature of bilingual language processing is intimately intertwined with the developmental profile of the brain. Because some brain areas develop earlier than others, this plays a role in the way in which early and late learners of a second language are instantiated in brain activity. That is, each language will take root in a network of brain areas depending on when that language is learned and at which rate it is learned.
An interesting aside here is the relatively slow development of the frontal lobes, which coincides with its slower developing ability to perform cognitive control tasks. In a similar vein, learning languages at different ages should be affected by and affect the particular control circuits used by different individuals. Although there are still many questions to answer and many puzzles to solve, this book will argue that the nonlinear dynamic models that have been used to uncover the underlying mechanisms seen in natural systems and more recently in language and cognition can be used to shed considerable light on the neural bases of bilingualism.
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Arturo Hernandez, who attained his doctorate in Cognitive Science and Psychology from the University of San Diego, is a Professor of Psychology and Director of the Developmental Cognitive Neuroscience graduate program at the University of Houston. His research centers on the neural underpinnings of bilingual language processing and second language acquisition in children and adults.
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Arturo speaks Spanish and English, which he learned as a child, Portuguese having spent two years in Brazil, and German.
