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Bilingualism and neuroplasticity : a casual mechanism of delay in cognitive decline

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Bilingualism and neuroplasticity : a casual mechanism of delay in cognitive decline
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Cillessen, Katie
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Metropolitan State University of Denver
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Bilingualism and Neuroplasticity: A Causal Mechanism of Delay in Cognitive Decline
by Katie Cillessen
An undergraduate thesis submitted in partial completion of the Metropolitan State University of Denver Honors Program
December 2015
Vicki Nilles Dr. Marina Gorlach Dr. Megan Hughes-Zarzo
Honors Program Director
Primary Advisor
Second Reader


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Introduction
The learning process is of utmost fascination especially when we examine the rippling effect it has had on a variety of fields. Every day we can learn something new if we keep the right attitude toward the experiences we encounter. Yet, many times we find that our viewpoint of an issue can be short term rather than long term. Still, every experience we encounter can have not only short, but also long term consequences that can be experienced for a long time, if not for the rest of our life.
Language learning in particular can completely change our life. When we initially learn our first language it is purely to communicate our needs before anything else. Yet when we learn a second language, the reasons for use can expand exponentially. Not only can a second language open the door to opportunities to understand various cultures, world views, and sentiments that are not normally prevalent in our own spectrum of society but it has been demonstrated to affect the neurological constructs of our physical makeup (Brynes, 2008). How exactly bilingualism affects our cognitive processes in particular could greatly impact the future of a variety of fields. By disseminating the manner in which the cognition of bilingual1 individuals is affected by the presence of two languages, I postulate that a manner in which the plasticity of our cognitive processes develop will come into focus and allow a dynamic understanding of the learning process to elevate.
Neuroanatomy of Language
As is commonly held as fact, and as is described by Pulvermuller (2012), neurons pass
1 For a definition of bilingual, as understood in their paper, please see the definition of key terms in the Appendix.


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signals of action potentials, at times via axons, to adjacent and distant neurons. This process is strengthened by repetition. After time, the repeated action causes the learned path of connection between neurons to strengthen. According to Pulvermuller (2012), this physiological principle of correlation learning also supports the theory that various brain regions are used in the production of language.
Since then, according to Pulvermuller (2012), a high volume of language related neurons are found in the cortex. This means that the action potentials would need to travel to other areas of the brain in order to acquire acoustic (in the temporal area), somatosensory (in the parietal area), and visual (in the occipital area) information. For example, the importance of acoustic input and language can be seen in the development of a fibre bundle of nerves between the cortex and temporal regions. This bundle is but one of three such bundles that make up the perislyvian cortex. This perisylvian cortex and these bundles are shown in figure 1 of the appendix.
As described by Pulvermuller (2012) figure 1 you see:
[The] blue areas [show] the superior-temporal cortex [which] include the primary auditory cortex (Al), the auditory belt (AB) and parabelt (PB) regions...[While the] red areas [refer to] ...the inferior-frontal cortex include inferior prefrontal (PF), premotor (PM) and primary motor cortex (Ml). Connections between these areas by way of white matter fibre tracts (arcuate fascicle, extreme capsule) are shown schematically by arrows. Language-relevant areas in the inferior-parietal cortex are not highlighted. Diagram at the bottom: The neural model of the language cortex (Garagnani et al., 2008) is shown, which mimics relevant areas and connections and is used to simulate language learning and brain responses to linguistic materials. Highlighted neural elements (circles) and


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connections (lines) indicate a distributed cell assembly linking action and perception circuits. This type of distributed circuit may underlie the production and recognition of spoken words (p. 428).
While the principle of correlation learning demonstrates how pathways between neurons are strengthened through use, the question of whether those are static or not is something that has become of interest in recent years. When we initially learn our first language (LI) we go through a process that is quite implicit in nature. Our linguistic competence is unconsciously obtained (Fromkin, Rodman & Hyam, 2014). Thus, a baby does not learn language by looking at grammar books, but rather by quietly watching their surrounding environment for clues about the makeup of their linguistic environment.
These stages of learning are highlighted by Ghasemi & Hashemi (2011). They note that the first stage of acquisition, which they call "Learning Sounds(p. 874), is when babies start to distinguish the phonemes that belong to their native language out of the hundred and fifty sounds that make up all the languages in the world today. This phonemic awareness is essential for them to move on to stage two, which they call "Learning Words (p. 874), in which meaning is added to the sounds that they now recognize.
The meaning of words not only has an object relevance but also is linked to more than just semantic knowledge (Pulvermuller, 2012). Action and emotional responses are developed and indexed until, at times, deep schemata are developed. This process is a continual and evolving one that never seems to stop since, even as an adult, new meaning can be attached to words that before did not hold any sentiment (Brynes, 2008). An example of this is when a new member is added to our family. Their name now takes on more meaning because it relates to who they are as a person, whereas beforehand it did not hold this additional meaning.


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The last stage in language learning discussed by Ghasemi & Hashemi (2011), which they call "Learning Sentences (p.874), is when the start of correct word order occurs. Grammatical laws come into play and with practice it is here that proficiency is reached, according to Ghasemi & Hashemi (2011). Each of these steps creates and strengthens the neural pathways that are related to correlation learning (Pulvermuller, 2012). As phonemes are linked to semantic knowledge within a host language neural pathways are strengthened. Yet there is debate over what occurs to the neural pathways when an individual becomes bilingual.
A study done by Klein, Mok, Chen, & Watkins (2014) recently examined the degree to which age of acquisition affected the structure of the brain and thus the neural pathways. One of the principle ways they did this was by measuring the cortical thickness of both bilingual and monolingual individuals. The groups that were included in their study were:
Monolinguals, Simultaneous bilinguals (individuals who learned two languages simultaneously between 0-3 years old), Early sequential bilinguals (individuals who learned their second language (L2) sequentially between the ages of 4-7), and, Late sequential bilinguals (individuals who learned their L2 sequentially between the ages of 8-13).
Socioeconomic status, education, and age (approximately) were all matched. The bilinguals were using both languages on a daily basis.
Once all analysis of the MR images demonstrating cortical thickness were disseminated via CIVET image processing pipeline, the results could be clearly defined (Klein et al., 2014). Notice figure 2 in the appendix which demonstrates the results. The areas where the cortical thickness is greater than the paired counterpart demonstrates that overall late bilingualism affects the cortical thickness to the greatest degree. The cortical thickness becomes greater in the left


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inferior frontal cortex, while it becomes thinner in the right frontal cortex. This is in harmony with another study that demonstrates acquisition of a second language before the age of six exhibits the involvement of both hemispheres whereas acquisition after the age of six exhibits left lateralization.
Leftward lateralization is something that Plante, Almryde, Patterson, Vance &
Asbjornsen (2015) examined. Commonly the thought that left lateral dominance of language development is inborn has been promoted, yet increasing evidence demonstrates a lack of cohesion regarding cortical asymmetries and language lateralization (p. 307). Therefore, Plante et al.(2015) set out to explore the theory that lateralization of cortical areas typically oriented with language functioning are affected by learning. In their study that included sixteen adult participants, with a mean age of twenty-four, similar neurologic disposition, and unfamiliarity with Norwegian language, the ability of participants to gain understanding of Norwegian after short exposure was studied.
Plante et al. (2015) discovered that a leftward shift in superior temporal gyri [STG] activation occurred during the subjects unguided learning of the unfamiliar language. This lateralization occurred over a period between twenty-five and thirty minutes, during which seven minute scans were conducted while they were exposed to the Norwegian language. As seen in figure 3 in the appendix, each scan showed a progression of leftward lateralization. As this result was produced in such short time, it gives rise to the question of whether maturation alone causes lateralization.
A study done by Martensson et al. (2012) further examined what happens to neural networks when adults learn a foreign language. The study examined a group of interpreters who learned a foreign language without any previous knowledge of it. The participants, in both the


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control group and studied group, were similar in age, years of education, emotional stability, and intelligence.
According to Martensson et al. (2012), the academy where the interpreters learned three different languages had a duration of ten months and required that the interpreters learn three-hundred to five-hundred words each week. Before the start of the program participants were imaged and after three months of this intense instruction they were imaged again. After the Freesurfer program, which uses MR volume to construct the image, produced a visual, the results could be examined. Please refer to figure 4 in the appendix for this image.
Figure 4 of the appendix demonstrates the average areas and percentage of cortical growth for the interpreters in the left hemisphere. It is of interest that these interpreters experienced significant growth of cortical thickness in the STG which is essential in acoustic-phonetic processes. The inferior frontal gyri (IFG) assists greatly in articulation. It is interesting to note the differences between this and a study done by Stein et al. (2012) that demonstrated the IFG cortical thickness grew in relation to the proficiency of the adult learner.
Alternatively, in the Martensson et al. (2012) study the cortical thickening of middle frontal gryi (MFG) was demonstrated to correlate to the proficiency of the adult learner as well as the degree to which effort was extended in the learning process. One reason that is mentioned for this possible difference by Martensson et al. (2012) is that in the study done by Stein et al.(2012) the levels of prior L2 presence were varied versus in the Martensson et al. (2012) study there was no previous knowledge of the L2 being acquired. Interestingly the MFG is also related to articulatory functioning and may also have a role in the control and planning of these processes.
Thus Martensson et al. (2012), makes the suggestion that their present results might


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suggest that the structural changes in the left frontal regions may reflect use- and demand-dependent changes rather than constitute the neural substrates of acquired language skill (p.243). The skill that is nominally used in language learning as emphasized by Bialystok, Craik & Luk (2012) is intense and sustained, but not one that is necessarily done due to talent or interest. This necessity requires not only acquiring of the L2, but also requires inhibition of LI use.
Higby, Kim & Obler (2013) mentions that bilinguals have greater developed higher cognitive function and executive control due to the need for them to inhibit use of one or more languages at a time. This inhibition comes at what Higby et al. (2013) describes as a switch cost which determines the effort of inhibition that it put into using the less prevalent language of the speaker. Thus, in line with Stocco, Yamasaki, Natalenko & Prat (2012), the language that one is less proficient in and uses less would take more effort for them to use while simultaneously not falling back on their more dominant language.
According to Higby et al. (2013), this has been shown to lead to a sharper "network of cognitive control of inhibition" (p.83) among bilinguals. This network emphasizes use of both the inferior parietal lobe and prefrontal cortex for executive function and inhibitory control. Additionally the anterior cingulate cortex comes into play for attention shifting and the left caudate for language shifting. This interwoven combination of brain regions and their adaptation to bilingualism affects an individual not only during use of the L2 but also restructures their whole linguistic system (Higby et al., 2013). We can thus see that according to Higby et al. (2013) the several facets of cognition are affected by bilingualism and that these are not singularly linguistic in nature. An example of this reorganization was examined by McAvoy et al. (2015). Their examination of the intrinsic resting state of language use found that there is a


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left lateral asymmetry for semantic processing while there is a rightward asymmetry for attention-related function.
Viewing language learning as similar to learning a new function, such as how to drive a car, play a sport, music, or dance, was something that Lukacs & Kemeny (2015) examined in their study. During their examination of this skill learning (SL) they aimed to discern what the best age range is for effective use of this type of learning. Their four-hundred and eighty participants had an age range from seven to eighty-seven. The participants capacity for SL was tested using a Serial Reaction Time Task (SRT) testing the learning of motor sequences, ... [a] [Artificial Grammar Learning] AGL task relying on the extraction of abstract regularities from auditory sequences, and... [a] WP [Weather Prediction] task examining non-sequential probabilistic categorization (p. 388). By following the results of these three tasks over a large population of subjects the thought was that similarity in processing would be shown; or the results would demonstrate the disunity of the SL process among individuals in a group.
Lukacs & Kemeny (2015) findings pointed unanimously to SL ability increasing with age. They demonstrate that performance peaks between eighteen and thirty-five and then has no, or mild, decline until sixty-five at which time a more significant drop in performance happens. While this is in contrast to an earlier study that demonstrated SL increased up to age fourteen and then decreased in efficiency over adulthood and further in the elderly, there are similarities between the two studies. The area they found similarities in is sequence learning. The comparable results demonstrated effectiveness of sequence learning increased from 4 to 12 years, stayed the same until the mid-thirties, and then declined into old age(p. 398).
Taking the results from Lukacs & Kemeny (2015), which are homogenous with the current studies on developmental differences in SL, we can see that age-related changes in the


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learning mechanism itself (p.400) are not a sole determinant of what age is most efficacious for SL. Maintaining this plastic view of the organization of learning networks as seen in relation to our main learning mechanism, or rather our brain, can be clearly seen in the neuroanatomy of traumatic brain injury patients and their ability to reorganize the brain in response to the imposed damage (Thompson, 2000; Elbert & Rockstroh, 2012; Smits et al., 2012).
As we have examined, adaptation of the brain in response to language is not only something that is attached to injury. At first when we are learning our LI and the fibre bundles are being created, links between basic functions essential to language learning are developing. Applying the principle of correlational learning, these pathways are continually strengthened with increased language use (Pulvermuller, 2012).
After the age of three a L2 has great impact on the cortical thickness of childhood learners (Klein et al. 2014). While cortical thickness continues to be affected primarily in the IFG up to age thirteen, from age thirteen onward SL seems to become less efficient (Lukacs & Kemeny, 2015). Yet it is the adult learner that tends to use more of the MFG region of the brain, which is commonly associated with executive control in L2 use (Martensson et al. 2012). As Higby et al. (2013) highlights, that the structural plasticity of the brain is affected is not a controversial topic. Yet, the areas that are affected and the manner in which they are affected in relation to age is still a matter for examination.
Later life cognition and cognitive decline
Examining how to mitigate the effects of cognitive decline is gaining attention especially since by the year 2050 the number of patients is expected to triple (Woumans et al. 2014). This deterioration has been shown to be linked with diseases such as dementia and Parkinsons. A


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possible precursor to the manifestation of these is seen in the growth of white matter lesions (WML) as well as the decrease in grey matter (GM) volume (Reji et al., 2012).
As examined by Reji et al. (2012), WMLs and their destructive path have been demonstrated to have a negative influence in later life cognition and lead to brain atrophy. Therefore the direction of their study was to examine what link there is between WML, GM volume, and thus cognitive decline. To do so they scanned two-thousand and one patients twice with a seven year resting period between scans. Seven hundred and forty of these patients exhibited cognitive decline.
The study of Refi et al. (2012) found that the greater the white matter grade (WMG), the greater the presence of small vascular disease (SVD), which is highly associated with both Alzheimers (AD) and mild cognitive impairment (MCI). Additionally it was found that both WMG and GM had both independent and overlapping areas affected. This overlapping can be seen in Figure 5 in the appendix.
Thus, the relationship between cognition, GM, WMG and, by consequence, WMLs in the study conducted by Refi et al. (2012) became clear. Related studies have also exhibited a relation executive dysfunction and GM atrophy in specific regions such as the STG. Any such structural and functional abnormalities can be a result of arterial stiffness, as highlighted by Vinogradov, Fisher, & Villers-Sidani (2012). Therefore, maintaining plasticity of these neural networks is of utmost importance.
According to Vinogradov et al. 2012, plasticity is a continuous process that adapts with age. A mature cortex achieves the most plasticity via attention-demanding intensive behavioral training strategies (p. 58). By manipulating attention, arousal, and reward mechanisms within the cortex these training strategies can become further useful and effective. Thus, while plasticity


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acquired via learning is possible, the behavior and attitude of the individual is also a major proponent.
The relationship between challenging cognitive activities and executive function, which has long been linked to GM volume (Reji et al. 2012), was further examined by Valian (2015). They examined the modulated effects of exercise, education, musical training, active video game playing, and, bilingualism for possible improvement in executive function in children, young adults, and older adults. For older adults they found that bilingualism was of greater benefit than it was to their counterparts since many of their group did not engage in the other challenging cognitive activities that were modulated. While Valian (2015) mentions that studies have shown a slowing of the onset of dementia and cognitive decline by up to four years, they also argue that the methods by which such studies are conducted need to be better regulated.
In addition to the studies mentioned in Valian (2015), the study conducted by Woumans et al. (2015) noticed a delay in the onset of dementia due to bilingualism. Of the one hundred and thirty-four native Belgians that were diagnosed with probable AD that participated in the study sixty-nine were monolingual and sixty-five were bilingual. In addition to LI, occupation, education level, gender, and, initial mental state were set as controls.
Upon examination of the age of manifestation results, and controlling the other predictors, the average age for monolinguals was seventy-one and a half while for bilinguals it was seventy-six point one. Thus, a four point six year delay in manifestation was distinctly exhibited. It is of note that these participants were making use of their L2 on a regular basis in their native country where their LI was the dominant language spoken. As explained by Valian (2015) this underlies their ability to actively maintain task goals and goal-related information (p. 5) while biasing lower level processing.


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According to Mitchell, Shaughnessy, Shirk, Yang, & Atri(2012), there is a relationship between task-related activation on a working memory task and measures of cognitive reserve (p. 1078). In their factor analysis of AD they aimed to measure the cognition reserve of patients that were diagnosed as among the spectrum from MCI to AD. They explored the degree to which proxies for cognitive reserve, such as years of education, active involvement in cognitively challenging activities, and, IQ, as well as constructs of processing resources, intellectual functioning, and, executive functioning, affected cognitive reserve in and of itself.
The results of factor analysis executed by Mitchell et al. (2012) validated cognitive reserve as a unique construct. Yet, it also demonstrated a correlation between cognitive reserve and processing speed/executive function. Interestingly these have an overlapping frontal network. Additionally, the network for cognitive reserve is also seen in the medial temporal areas. Both of these regions have been indicated as areas involved in L2 acquisition. Therefore, upon understanding this close relationship as well as the effect on the delay on the onset of dementia, the author endorses bilingualism as a deterrent of cognitive decline.
Educational Implications
As examined, the process of learning our LI is not generally completed in an educational institution setting. Rather, this learning process is quite implicit in nature. Yet, as we have also seen, adults have the ability to implicitly learn (Plante et al. 2015). In just thirty minutes the subjects of the Plante et al. study were able to lateralize the unfamiliar language unguided by any influence other than their own.
Leftward lateralization is in harmony with the learning biases hypothesis that Plante et al. (2015) expounds as the theory that language lateralization is not an inborn property of brain


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organization but rather due to the recruitment of the mainly left hemispheric neural resources. With repeated exposure to a language, the recruitment of these neural resources increases due to the language becoming recognized as communication. This causes rather basic neural resources to become integral in the acquisition of the language. The learning biases hypothesis is in harmony with the description Pulvermuller, (2012) gives of correlational learning and the subsequent creation of neural pathways.
The procedural and implicit process of creating correlational learned pathways in LI acquisition led to the thought that, according to Archila-Suerte, Zevin, Bunta, & Hernandez (2012), [a]s native language input increases, children become neurally committed to the phonetic system to which they are exposed (p. 191) and thus early distortion to the neural network would inhibit native-like acquisition of a L2 later in life. Yet in their study, proficiency was found to be the major factor. The participants included four groups comprised of early, intermediate, and late English/Spanish bilinguals and English monolinguals residing in the United States. They were asked to complete a picture vocabulary, listening comprehension, and, similarity judgement task to demonstrate their ability to distinguish the phonemes of each language as well as determine their individual proficiency.
The results of the Archila-Suerte et al. (2012) study exhibited that contrary to the thought native-like acquisition of an L2 could not happen later in life, having high exposure and proficiency in their L2 determined the late bilinguals ability to distinguish the phonemes relative to each language. Additionally, it was exhibited that radical neural changes due to manipulation of two phonetic codes occurs only if the late bilinguals had a high proficiency in their L2. In bilinguals who acquire their L2 before the age of four, the underdevelopment of the prefrontal cortex may add to their ability to learn language implicitly (Wei et al. 2015).


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Yet a highly proficient learner, which only comes with years of practice, has shown to recruit bilateral parietal and frontal lobe regions that are known for their role in attention (Archila-Suerte et al. 2012). Development of these two codes, or neural pathways, thus generates neural plasticity. According to Dubinsky, Roehrig, &Varma(2013), plasticity can be described as relating to the strength of the synaptic connections between neurons [being] dynamic, becoming stronger with use or weaker with inactivity, providing a cellular-level signal that reflects the history of activity (p. 318). Understanding that learning takes place in response to all experiences we encounter allows learners to develop a plastic view of their ability to learn.
Viewing language learning as a dynamic process is further demonstrated in the study conducted by Leung & Williams (2014). They examined thirty native English speakers, and twenty-seven native Chinese speakers all with varying L2 levels and asked them to determine the grammatical correctness of a couple hundred noun phrases. The results from one of their experiments exhibited that implicit bidirectional knowledge had some effect on the ability to decipher the article and anomaly of each respective language. The cross-linguistic influences that their participants experienced over all of their experiments demonstrated that learning often involves both explicit and implicit learning (p. 753). Yet they postulate it remains unclear to what degree such influences take place implicitly, explicitly, or both implicitly and explicitly, in different L2 acquisition settings, and it seems likely that individual differences exist (p.753).
As evidence increasingly points to a plastic view of learning, the manner that learning happens within an educational setting needs to adapt as well. Often curricula continues to rely on antiquated views that are heavily imbedded with a static understanding of learning that contrastingly has been seen to be a dynamic process. Perceiving learning, and language learning in particular, as a dynamic system Optiz (2012) describes language development as able to be


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molded by interrelated networks of social interaction, experience and cognitive processes (p.702).
Relationally then, what can seem like unrelated linguistic phenomena (p. 702) can actually be housed within one theoretical approach. Theories such as dynamic systems theory (DST), which is distinguished as being adaptive, complex, and in constant flux, allows for a nonlinear view of language to be explored. Seeing the interconnection between environment and the nonlinearity interaction within the linguistic system begs for further adaptations to be explored within educational systems.
Conclusion
In this exploration of the changes in neuroanatomy in response to the presence of two linguistic communities and the possible corresponding plasticity hosted within the cognitive processes we have seen arguments from various sources. Initially we see from Pulvermuller et al. (2012) that correlational learning is essential in the acquisition of language. Ghasemi & Hashemi (2011) demonstrated how this process is essential in LI acquisition. The structural changes to these pathways have been highlighted by several of the studies. While childhood bilinguals can demonstrate this response in thickening and thinning cortical thickness within the left and right IFG. Adult bilinguals tend to show growth of GM in the MFG as well as STG. These areas are related to executive control function.
Seeing this relation is especially of interest when we examine the location of WMG later in life and see that there is a high correlation between executive dysfunction, GM atrophy in regions of the STG. While other challenging cognitive activities have been explored and shown to affect this WMG and slow the onset of AD, language learning is a challenging cognitive


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activity that can continue well into the later years of life. Acquisition of a L2 in adulthood may cause a sense of panic in contrast to the implicit nature of learning that was most likely experienced with the LI. Yet this panic has been shown to be necessary since even adults can learn implicitly, and in conjunction with the higher cognitive function that has developed, build their proficiency.
Gaining further understanding of the plastic nature of our neuroanatomy and the adaptation that has been demonstrated both in response to language learning, aging, and educational stimuli, as well as the bridges between these areas can continue to mold the manner in which both educators and learners approach learning. As the cognitive process of learning and the possible long term effects that bilingualism can have are explored, examining these processes as dynamic is essential if we are to understand the extent of learning process flexibility.


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Appendix
Definition of key terms:
Bilingual-
The term bilingual has long been used when we are discussing two or more languages (Cenoz, 2013). Yet, the dispute comes into play when we consider whether the degree of use of the two languages is necessary of accounting or not. For example, a person may understand two separate languages, but does not use one of the two very often. This in turn can affect the proficiency with which they can maneuver the language.
According to Grosjean (2010) bilinguals can be defined as those who use two or more languages (or dialects) in their everyday lives. Yet according to Li, as quoted in Cenoz (2013), anyone who can communicate in more than one language, be it active (through speaking and writing) or passive (through listening and reading) (p. 5) is considered to be bilingual. Thus, Grosjean is in favor of use and Li is in favor of proficiency. There are disadvantages and


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advantages to both viewpoints. With Grosjean the question of what constitutes use is left to the wayside, while with Li the question of what constitutes communication and what constitutes language is left without answer.
A conjoined representation of both is what we will use for the purposes of our examination. Therefore being bilingual refers to an individual that communicates in at least two languages (or dialects) via either active or passive use in their regular life. Maintaining this balanced view of bilingualism will allow us to view current studies in a holistic manner.
Figures: Figure 1


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M1 PM PF PB AB A1


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Figure 2
Monolingual Early
4.8
4.6
4.4
4.2 4.0
3.8
3.6
3.4
3.2
Monolingual Late
Late Bilingual < Early Bilingual
3.6 3.5 3.4
3.3
3.2
Early Late
2
(b)
Late Bilingual > Monolingual
Monolingual Late
(d)
Late Bilingual < Simultaneous Bilingual
4
4.8 i
4.6 J
4.4 \
4.2 \ 4.0 J
3.8 \
3.6 J
3.4 J
3.2 I
Monolingual
Early


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Figure 3


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Figure 4


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Figure 5


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References
Bialystok, E., Craik, F., & Luk, G. (2012). Bilingualism: Consequences for mind and brain. Trends in Cognitive Sciences, 16(4), 240-250. doi: 10.1016/j.tics.2012.03.001
Byrnes, J. (2008). Cognitive development and learning in instructional contexts (3rd ed.). Boston, Massachusetts: Pearson Education.
Cenoz, J. (2013). Defining Multilingualism. Annual Review of Applied Linguistics, 33, 3-18. doi: 10.1017/S0267190513 00007X
Dubinsky, J., Roehrig, G., & Varma, S. (2013). Infusing Neuroscience Into Teacher Professional Development. Educational Researcher, 42(6), 317-329. doi: 10.3102/0013189X13499403
Elbert, T., & Rockstroh, B. (2004). Reorganization of Human Cerebral Cortex: The Range of Changes Following Use and Injury. The Neuroscientist, 10(2), 129-141.
doi: 10.1177/1073858403262111


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Fromkin, V., Rodman, R., & Hyams, N. (2013). An introduction to language (10th ed.). New York, New York: Wadsworth Publishing.
Ghasemi, B., & Hashemi, M. (2011). Foreign Language Learning During Childhood. Procedia -Social and Behavioral Sciences, 28, 872-876. doi: 10.1016/j.sbspro.2011.11.160
Grosjean, F. (2010). Bilingual life and reality. Cambridge, Massachusetts: Harvard University Press.
Higby,, E., Jungna, K., & Obler, L. (2013). Multilingualism and the Brain. Annual Review of Applied Linguistics, 33, 68-101. doi:10.1017/S0267190513000081
Klein, D., Mok, K., Chen, J., & Watkins, K. (2014). Age of language learning shapes brain
structure: A cortical thickness study of bilingual and monolingual individuals. Brain and Language, 131, 20-24. http://dx.doi.Org/10.1016/i.bandl.2013.05.014
Liu, H., Fan, N., Rossi, S., Yao, P., & Chen, B. (2015). The effect of cognitive flexibility on task switching and language switching. International Journal of Bilingualism, 1-17. doi:10.1177/1367006915572400
Lukacs, A, & Kemeny, F. (2015). Development of Different Forms of Skill Learning Throughout the Lifespan. Cognitive Science A Multidisciplinary Journal, 39(2), 383-404.


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doi:10.1111/cogs.l2143
McAvoy, M., Mitra, A., Coalson, R., D'avossa, G., Keidel, J., Petersen, S., & Raichle, M. (2015). Unmasking Language Lateralization in Human Brain Intrinsic Activity. Cerebral Cortex, 1-14. doi:10.1093/cercor/bhv007
Mitchell, M., Shaughnessy, L., Shirk, S., Yang, F., & Atri, A. (2012). Neuropsychological Test Performance and Cognitive Reserve in Healthy Aging and the Alzheimer's Disease Spectrum: A Theoretically Driven Factor Analysis. Journal of the International Neuropsychological Society, 18, 1071-1080. doi:10.1017/S1355617712000859
Martensson, J., Eriksson, J., Bodammer, N., Lindgren, M., Johansson, M., Nyberg, L., & Lovden, M. (2012). Growth of language-related brain areas after foreign language learning. Neuroimage, 63, 240-244. doi: 10.1016/j.neuroimage.2012.06.043
Plante, E., Almryde, K., Patterson, D., Vance, C., & Asbjornsen, A. (2015). Language
lateralization shifts with learning by adults. Laterality: Asymmetries of Body, Brain and Cognition, 20(3), 306-325. doi:10.1080/1357650X.2014.963597
Pulvermuller, F. (2012). Meaning and the brain: The neurosemantics of referential, interactive, and combinatorial knowledge. Journal of Neurolinguistics, 25(5), 423-459. doi: 10.1016/j .jneuroling.2011.03.004


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Raji, C., Lopez, O., Kuller, L., Carmichael, O., Longstreth, W., Gach, H., Becker, J. (2012). White matter lesions and brain gray matter volume in cognitively normal elders. Neurobiology of Aging, 33(4), 834.e7-834.el6. doi: 10.1016/j. neurobiol aging.2011.08.010
Smits, M., Visch-Brink, E., Sandt-Koenderman, M., & Lugt, A. (2012). Advanced Magnetic Resonance Neuroimaging of Language Function Recovery After Aphasic Stroke: A Technical Review. Archives of Physical Medicine and Rehabilitation, 93(1), S4-S14. doi: 10.1016/j.apmr.2011.02.023
Stein, M., Federspiel, A., Koenig, T., Wirth, M., Strik, W., Wiest, R., Dierks, T. (2012). Structural plasticity in the language system related to increased second language proficiency. Cortex, 48(4), 458-465. doi: 10.1016/j.cortex.2010.10.007
Stocco, A., Yamasaki, B., Natalenko, R., & Prat, C. (2014). Bilingual brain training: A
neurobiological framework of how bilingual experience improves executive function. International Journal of Bilingualism, 75(1), 67-92. doi: 10.1177/1367006912456617
Thompson, C. (2000). NEUROPLASTICITY: EVIDENCE FROM APHASIA. Journal of Communication Disorders, 33(4), 357-366. doi:10.1016/S0021-9924(00)00031-9


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Valian, V. (2015). Bilingualism and cognition. Bilingualism: Language and Cognition, 18( 1), 3-24. doi: 10.1017/S1366728914000522
Vinogradov, S., Fisher, M., & Villers-Sidani, E. (2012). Cognitive Training for Impaired Neural Systems in Neuropsychiatric Illness. Neuropsychopharmacology, 37(1), 43-76. doi: 10.103 8/npp.2011.251
Wei, M., Joshi, A., Zhang, M., Mei, L., Manis, F., He, Q., Lu, Z. (2015). How age of
acquisition influences brain architecture in bilinguals. Journal of Neurolinguistics, 36, 35-55. doi:dx.doi.org/10.1016/j.jneuroling.2015.05.001
Woumans, E., Santens, P., Sieben, A., Versijpt, J., Stevens, M., & Duyck, W. (2015).
Bilingualism delays clinical manifestation of Alzheimer's disease. Bilingualism: Language and Cognition, 568-574. doi::10.1017/S136672891400087X


Full Text

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Bilingualism and Neuroplasticity: A Causal Mechanism of Delay in Cognitive Decline by Katie Cillessen An undergraduate thesis submitted in partial completion of the M etropolitan State University of D enver Honors Program December 2015 Vicki Nilles Dr. Marina Gorlach Dr. Megan Hughes Zarzo Primary Advisor Second Reader Honors Program Director

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A Dynamic Viewpoint Cillessen 1 Introduction The learning process is of utmost fascination especially when we examine the rippling effect it has had on a variety of fields. Every day we can learn something new if we keep the right attitude toward the experiences we encounter. Yet, many times we find that our viewpoint of an issue can be short term rather than long term. Still, every experience we encounter can have not only short, but also long term consequences that can be experienced for a long time, if not for the rest of our life. Language lear ning in particular can completely change our life. When we initially learn our first language it is purely to communicate our needs before anything else. Yet when we learn a second language, the reasons for use can expand exponentially. Not only can a seco nd language open the door to opportunities to understand various cultures, world views, and sentiments that are not normally prevalent in our own spectrum of society but it has been demonstrated to affect the neurological constructs of our physical makeup (Brynes, 2008). How exactly bilingualism affects our cognitive processes in particular could greatly impact the future of a variety of fields. By disseminating the manner in which the cognition of bilingual 1 individuals is affected by the presence of two l anguages, I postulate that a manner in which the plasticity of our cognitive processes develop will come into focus and allow a dynamic understanding of the learning process to elevate. Neuroanatomy of Language As is commonly held as fact, and as is desc ribed by Pulverm Ÿller (2012), neurons pass 1 For a definition of bilingual, as understood in their paper, please see the definition of key terms in the Appendix.

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A Dynamic Viewpoint Cillessen 2 signals of action potentials, at times via axons, to adjacent and distant neurons. This process is strengthened by repetition. After time, the repeated action causes the learned path of connection between neurons to strengthen. According to PulvermŸller (2012), this physiological principle of correlation learning also supports the theory that various brain regions are used in the production of language. Since then, according to PulvermŸller (2012), a high volume of language related neurons are found in the cortex. This means that the action potentials would need to travel to other areas of the brain in order to acquire acoustic (in the temporal area), somatosensory (in the parietal area), and visual (in the occip ital area) information. For example, the importance of acoustic input and language can be seen in the development of a fibre bundle of nerves between the cortex and temporal regions. This bundle is but one of three such bundles that make up the perislyvian cortex. This perisylvian cortex and these bundles are shown in figure 1 of the appendix. As described by PulvermŸller (2012) figure 1 you see: [The] blue areas [show] the superior temporal cortex [which] include the primary auditory cortex (A1), the auditory belt (AB) and parabelt (PB) regions...[While the] red areas [refer to] ...the inferior frontal cortex include inferior prefrontal (PF), premotor (PM) and primary motor cortex (M1). Connections between these areas by way of white matter fibre tracts (arcuate fascicle, extreme capsule) are shown schematically by arrows. Language relevant areas in the inferior parietal cortex are not highlighted. Diagram at the bottom: The neural model of the language cortex (Garagnani et al., 2008) is shown, which mimics relevant areas and connections and is used to simulate language learning and brain responses to linguistic materials. Highlighted neural elements (circles) and

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A Dynamic Viewpoint Cillessen 3 connections (lines) indicate a distributed cell assembly linking action and perception circuits. This type of distributed circuit may underlie the production and recognition of spoken words (p. 428). While the principle of correlation learning demonstrates how pathways between neurons are strengthened through use, the questi on of whether those are static or not is something that has become of interest in recent years. When we initially learn our first language (L1) we go through a process that is quite implicit in nature. Our linguistic competence is unconsciously obtained (F romkin, Rodman & Hyam, 2014). Thus, a baby does not learn language by looking at grammar books, but rather by quietly watching their surrounding environment for clues about the makeup of their linguistic environment. These stages of learning are highlight ed by Ghasemi & Hashemi (2011). They note that the first stage of acquisition, which they call "Learning Sounds"(p. 874), is when babies start to distinguish the phonemes that belong to their native language out of the hundred and fifty sounds that make up all the languages in the world today. This phonemic awareness is essential for them to move on to stage two, which they call "Learning Words" (p. 874), in which meaning is added to the sounds that they now recognize. The meaning of words not only has an object relevance but also is linked to more than just semantic knowledge (PulvermŸller, 2012). Action and emotional responses are developed and indexed until, at times, deep schemata are developed. This process is a continual and evolving one that never s eems to stop since, even as an adult, new meaning can be attached to words that before did not hold any sentiment (Brynes, 2008). An example of this is when a new member is added to our family. Their name now takes on more meaning because it relates to who they are as a person, whereas beforehand it did not hold this additional meaning.

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A Dynamic Viewpoint Cillessen 4 The last stage in language learning discussed by Ghasemi & Hashemi (2011), which they call "Learning Sentences" (p.874), is when the start of correct word order occurs. Gra mmatical laws come into play and with practice it is here that proficiency is reached, according to Ghasemi & Hashemi (2011). Each of these steps creates and strengthens the neural pathways that are related to correlation learning (PulvermŸller, 2012). As phonemes are linked to semantic knowledge within a host language neural pathways are strengthened. Yet there is debate over what occurs to the neural pathways when an individual becomes bilingual. A study done by Klein, Mok, Chen, & Watkins (2014) recentl y examined the degree to which age of acquisition affected the structure of the brain and thus the neural pathways. One of the principle ways they did this was by measuring the cortical thickness of both bilingual and monolingual individuals. The groups th at were included in their study were: Monolinguals, Simultaneous bilinguals (individuals who learned two languages simultaneously between 0 3 years old), Early sequential bilinguals (individuals who learned their second language (L2) sequentially be tween the ages of 4 7), and, Late sequential bilinguals (individuals who learned their L2 sequentially between the ages of 8 13). Socioeconomic status, education, and age (approximately) were all matched. The bilinguals were using both languages on a d aily basis. Once all analysis of the MR images demonstrating cortical thickness were disseminated via CIVET image processing pipeline, the results could be clearly defined (Klein et al., 2014). Notice figure 2 in the appendix which demonstrates the resu lts. The areas where the cortical thickness is greater than the paired counterpart demonstrates that overall late bilingualism affects the cortical thickness to the greatest degree. The cortical thickness becomes greater in the left

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A Dynamic Viewpoint Cillessen 5 inferior frontal cortex while it becomes thinner in the right frontal cortex. This is in harmony with another study that demonstrates acquisition of a second language before the age of six exhibits the involvement of both hemispheres whereas acquisition after the age of six exh ibits left lateralization. Leftward lateralization is something that Plante, Almryde, Patterson, Vance & Asbj rnsen (2015) examined. Commonly the thought that left lateral dominance of language development is inborn has been promoted, yet increasing evi dence demonstrates a lack of cohesion regarding "cortical asymmetries and language lateralization" (p. 307). Therefore, Plante et al.(2015) set out to explore the theory that lateralization of cortical areas typically oriented with language functioning are affected by learning. In their study that included sixteen adult participants, with a mean age of twenty four, similar neurologic disposition, and unfamiliarity with Norwegian language, the ability of participants to gain understanding of Norwegian after short exposure was studied. Plante et al. (2015) discovered that a leftward shift in superior temporal gyri [STG] activation occurred during the subjects unguided learning of the unfamiliar language. This lateralization occurred over a period between twe nty five and thirty minutes, during which seven minute scans were conducted while they were exposed to the Norwegian language. As seen in figure 3 in the appendix, each scan showed a progression of leftward lateralization. As this result was produced in su ch short time, it gives rise to the question of whether maturation alone causes lateralization. A study done by MÂŒrtensson et al. (2012) further examined what happens to neural networks when adults learn a foreign language. The study examined a group of i nterpreters who learned a foreign language without any previous knowledge of it. The participants, in both the

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A Dynamic Viewpoint Cillessen 6 control group and studied group, were similar in age, years of education, emotional stability, and intelligence. According to M ÂŒrtensson et al. (2012), the academy where the interpreters learned three different languages had a duration of ten months and required that the interpreters learn three hundred to five hundred words each week. Before the start of the program participants were imaged and after three months of this intense instruction they were imaged again. After the Freesurfer program, which uses MR volume to construct the image, produced a visual, the results could be examined. Please refer to figure 4 in the appendix for this image. F igure 4 of the appendix demonstrates the average areas and percentage of cortical growth for the interpreters in the left hemisphere. It is of interest that these interpreters experienced significant growth of cortical thickness in the STG which is essenti al in acoustic phonetic processes. The inferior frontal gyri (IFG) assists greatly in articulation. It is interesting to note the differences between this and a study done by Stein et al. (2012) that demonstrated the IFG cortical thickness grew in relation to the proficiency of the adult learner. Alternatively, in the MÂŒrtensson et al. (2012) study the cortical thickening of middle frontal gryi (MFG) was demonstrated to correlate to the proficiency of the adult learner as well as the degree to which ef fort was extended in the learning process. One reason that is mentioned for this possible difference by MÂŒrtensson et al. (2012) is that in the study done by Stein et al.(2012) the levels of prior L2 presence were varied versus in the MÂŒrtensson et al. (2 012) study there was no previous knowledge of the L2 being acquired. Interestingly the MFG is also related to articulatory functioning and may also have a role in the control and planning of these processes. Thus MÂŒrtensson et al. (2012), makes the sugg estion that their "present results might

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A Dynamic Viewpoint Cillessen 7 suggest that the structu ral changes in the left frontal regions may reflect use and demand dependent changes rather than constitute the neural substrates of acquired language skill" (p.243). The skill that is nominally used in language learning as emphasized by Bialystok, Craik & Luk (2012) is intense and sustained, but not one that is necessarily done due to talent or interest. This necessity requires not only acquiring of the L2, but also requires inhibition of L1 use. Higby Kim & Obler (2013) mentions that bilinguals have greater developed higher cognitive function and executive control due to the need for them to inhibit use of one or more languages at a time. This inhibition comes at what Hig by et al. (20 13) describes as a switch cost which determines the effort of inhibition that it put into using the less prevalent language of the speaker. Thus, in line with Stocco, Yamasaki, Natalenko & Prat (2012), the language that one is less proficient in and uses less would take more effort for them to use while simultaneously not falling back on their more dominant language. According to Hig by et al. (2013), this has been shown to lead to a sharper "network of cognitive control of inhibition" (p.83) among bilingu als. This network emphasizes use of both the inferior parietal lobe and prefrontal cortex for executive function and inhibitory control. Additionally the anterior cingulate cortex comes into play for attention shifting and the left caudate for language shi fting. This interwoven combination of brain regions and their adaptation to bilingualism affects an individual not only during use of the L2 but also restructures their whole linguistic system (Higby et al., 2013). We can thus see that according to Hig by e t al. (2013) the several facets of cognition are affected by bilingualism and that these are not singularly linguistic in nature. An example of this reorganization was examined by McAvoy et al. (2015). Their examination of the intrinsic resting state of l anguage use found that there is a

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A Dynamic Viewpoint Cillessen 8 left lateral asymmetry for semantic processing while there is a rightward asymmetry for attention related function. Viewing language learning as similar to learning a new function, such as how to drive a car, play a spor t, music, or dance, was something that Luk‡cs & KemŽny (2015) examined in their study. During their examination of this skill learning (SL) they aimed to discern what the best age range is for effective use of this type of learning. Their four hundred and eighty participants had an age range from seven to eighty seven. The participants' capacity for SL was tested using a "Serial Reaction Time Task (SRT) testing the learning of motor sequences, [a] [Artificial Grammar Learning] AGL task relying on the extra ction of abstract regularities from auditory sequences, and[a] WP [Weather Prediction] task examining non sequential probabilistic categorization" (p. 388). By following the results of these three tasks over a large population of subjects the thought was that similarity in processing would be shown; or the results would demonstrate the disunity of the SL process among individuals in a group. Luk‡cs & KemŽny (2015) findings pointed unanimously to SL ability increasing with age. They demonstrate that perf ormance peaks between eighteen and thirty five and then has no, or mild, decline until sixty five at which time a more significant drop in performance happens. While this is in contrast to an earlier study that demonstrated SL increased up to age fourteen and then decreased in efficiency over adulthood and further in the elderly, there are similarities between the two studies. The area they found similarities in is sequence learning. The comparable results demonstrated effectivene ss of sequence learning in creased from 4 to 12 years, stayed the same until the mid thirties, and then declined into old age"(p. 398). Taking the results from Luk‡cs & KemŽny (2015), which are homogenous with the current studies on developmental differences in SL, we can see that "age related changes in the

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A Dynamic Viewpoint Cillessen 9 learning mechanism itself" (p.400) are not a sole determinant of what age is most efficacious for SL. Maintaining this plastic view of the organization of learning networks as seen in relation to our main learning mechanism, or rather our brain, can be clearly seen in the neuroanatomy of traumatic brain injury patients and their ability to reorganize the brain in response to the imposed damage (Thompson, 2000; Elbert & Rockstroh, 2012; Smits et al., 2012). As we have examined, a daptation of the brain in response to language is not only something that is attached to injury. At first when we are learning our L1 and the fibre bundles are being created, links between basic functions essential to language learning are developing. Appl ying the principle of correlational learning, these pathways are continually strengthened with increased language use (Pulverm Ÿller, 2012). After the age of three a L2 has great impact on the cortical thickness of childhood learners (Klein et al. 2014). While cortical thickness continues to be affected primarily in the IFG up to age thirteen, from age thirteen onward SL seems to become less efficient (Luk‡cs & KemŽny, 2015). Yet it is the adult learner that tends to use more of the MFG region of the brain which is commonly associated with executive control in L2 use (M Œ rtens son et al. 2012) As Higby et al. (2013) highlights, that the structural plasticity of the brain is affected is not a controversial topic. Yet, the areas that are affected and the mann er in which they are affected in relation to age is still a matter for examination. Later life cognition and cognitive decline Examining how to mitigate the effects of cognitive decline is gaining attention especially since by the year 2050 the number o f patients is expected to triple (Woumans et al. 2014). This deterioration has been shown to be linked with diseases such as dementia and Parkinson 's. A

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A Dynamic Viewpoint Cillessen 10 possible precursor to the manifestation of these is seen in the growth of white matter lesions (WML) a s well as the decrease in grey matter (GM) volume (Reji et al., 2012). As examined by Reji et al. (2012), WML's and their destructive path have been demonstrated to have a negative influence in later life cognition and lead to brain atrophy. Therefore th e direction of their study was to examine what link there is between WML, GM volume, and thus cognitive decline. To do so they scanned two thousand and one patients twice with a seven year resting period between scans. Seven hundred and forty of these pati ents exhibited cognitive decline. The study of Refi et al. (2012) found that the greater the white matter grade (WMG), the greater the presence of small vascular disease (SVD), which is highly associated with both Alzheimers (AD) and mild cognitive impai rment (MCI). Additionally it was found that both WMG and GM had both independent and overlapping areas affected. This overlapping can be seen in Figure 5 in the appendix. Thus, the relationship between cognition, GM, WMG and, by consequence, WML's in the study conducted by Refi et al. (2012) became clear. Related studies have also exhibited a relation executive dysfunction and GM atrophy in specific regions such as the STG. Any such structural and functional abnormalities can be a result of arterial st iffness, as highlighted by Vinogradov, Fisher, & Villers Sidani (2012). Therefore, maintaining plasticity of these neural networks is of utmost importance. According to Vinogradov et al. 2012, plasticity is a continuous process that adapts with age. A mat ure cortex achieves the most plasticity via "attention demanding intensive behavioral training strategies" (p. 58). By manipulating attention, arousal, and reward mechanisms within the cortex these training strategies can become further useful and effectiv e. Thus, while plasticity

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A Dynamic Viewpoint Cillessen 11 acquired via learning is possible, the behavior and attitude of the individual is also a major proponent. The relationship between challenging cognitive activities and executive function, which has long been linked to GM volume ( Reji et al. 2012), was further examined by Valian (2015). They examined the modulated effects of exercise, education, musical training, active video game playing, and, bilingualism for possible improvement in executive function in children, young adults, a nd older adults. For older adults they found that bilingualism was of greater benefit than it was to their counterparts since many of their group did not engage in the other challenging cognitive activities that were modulated. While Valian (2015) mentions that studies have shown a slowing of the onset of dementia and cognitive decline by up to four years, they also argue that the methods by which such studies are conducted need to be better regulated. In addition to the studies mentioned in Valian (2015), the study conducted by Woumans et al. (2015) noticed a delay in the onset of dementia due to bilingualism. Of the one hundred and thirty four native Belgians that were diagnosed with probable AD that participated in the study sixty nine were monolingual a nd sixty five were bilingual. In addition to L1, occupation, education level, gender, and, initial mental state were set as controls. Upon examination of the age of manifestation results, and controlling the other predictors, the average age for monoling uals was seventy one and a half while for bilinguals it was seventy six point one. Thus, a four point six year delay in manifestation was distinctly exhibited. It is of note that these participants were making use of their L2 on a regular basis in their na tive country where their L1 was the dominant language spoken. As explained by Valian (2015) this underlies their ability to "actively maintain task goals and goal related information" (p. 5) while biasing lower level processing.

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A Dynamic Viewpoint Cillessen 12 According to Mitchell, Sha ughnessy, Shirk, Yang, & Atri (2012), there is a relationship between "task related activation on a working memory task and measures of cognitive reserve" (p. 1078). In their factor analysis of AD they aimed to measure the cognition reserve of patients tha t were diagnosed as among the spectrum from MCI to AD. They explored the degree to which proxies for cognitive reserve, such as years of education, active involvement in cognitively challenging activities, and, IQ, as well as constructs of processing resou rces, intellectual functioning, and, executive functioning, affected cognitive reserve in and of itself. The results of factor analysis executed by Mitchell et al. (2012) validated cognitive reserve as a unique construct. Yet, it also demonstrated a corr elation between cognitive reserve and processing speed/executive function. Interestingly these have an overlapping frontal network. Additionally, the network for cognitive reserve is also seen in the medial temporal areas. Both of these regions have been i ndicated as areas involved in L2 acquisition. Therefore, upon understanding this close relationship as well as the effect on the delay on the onset of dementia, the author endorses bilingualism as a deterrent of cognitive decline. Educational Implications As examined, the process of learning our L1 is not generally completed in an educational institution setting. Rather, this learning process is quite implicit in nature. Yet, as we have also seen, adults have the ability to implicitly learn (Plante et al. 2015). In just thirty minutes the subjects of the Plante et al. study were able to lateralize the unfamiliar language unguided by any influence other than their own. Leftward lateralization is in harmony with the learning biases hypothesis that Plante e t al. (2015) expounds as the theory that language lateralization is not an inborn property of brain

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A Dynamic Viewpoint Cillessen 13 organization but rather due to the recruitment of the mainly left hemispheric neural resources. With repeated exposure to a language, the recruitment of the se neural resources increases due to the language becoming recognized as communication. This causes rather basic neural resources to become integral in the acquisition of the language. The learning biases hypothesis is in harmony with the description Pulve rmŸller, (2012) gives of correlational learning and the subsequent creation of neural pathways. The procedural and implicit process of creating correlational learned pathways in L1 acquisition led to the thought that, according to Archila Suerte, Zevin, Bunta, & Hernandez (2012), "[a] s native language input increases, children become neurally committed to the phonetic system to which they are exposed" (p. 191) and thus early distortion to the neural network would inhibit native like acquisition of a L2 la ter in life. Yet in their study, proficiency was found to be the major factor. The participants included four groups comprised of early, intermediate, and late English/Spanish bilinguals and English monolinguals residing in the United States. They were ask ed to complete a picture vocabulary, listening comprehension, and, similarity judgement task to demonstrate their ability to distinguish the phonemes of each language as well as determine their individual proficiency. The results of the Archila Suerte et al. (2012) study exhibited that contrary to the thought native like acquisition of an L2 could not happen later in life, having high exposure and proficiency in their L2 determined the late bilinguals' ability to distinguish the phonemes relative to each l anguage. Additionally, it was exhibited that radical neural changes due to manipulation of two phonetic codes occurs only if the late bilinguals had a high proficiency in their L2. In bilinguals who acquire their L2 before the age of four, the underdevelop ment of the prefrontal cortex may add to their ability to learn language implicitly (Wei et al. 2015).

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A Dynamic Viewpoint Cillessen 14 Yet a highly proficient learner, which only comes with years of practice, has shown to recruit bilateral parietal and frontal lobe regions that are kno wn for their role in attention (Archila Suerte et al. 2012). Development of these two codes, or neural pathways, thus generates neural plasticity. According to Dubinsky, Roehrig, &Varma (2013), plasticity can be described as relating to the "strength of th e synaptic connections between neurons [being] dynamic, becoming stronger with use or weaker with inactivity, providing a cellular level signal that reflects the history of activity" (p. 318). Understanding that learning takes place in response to all expe riences we encounter allows learners to develop a plastic view of their ability to learn. Viewing language learning as a dynamic process is further demonstrated in the study conducted by Leung & Williams (2014). They examined thirty native English speaker s, and twenty seven native Chinese speakers all with varying L2 levels and asked them to determine the grammatical correctness of a couple hundred noun phrases. The results from one of their experiments exhibited that implicit bidirectional knowledge had some effect on the ability to decipher the article and anomaly of each respective language. The cross linguistic influences that their participants experienced over all of their experiments demonstrated "that learning often involves both explicit and impli cit learning" (p. 753). Yet they postulate it remains "unclear to what degree such influences take place implicitly, explicitly, or both implicitly and explicitly, in different L2 acquisition settings, and it seems likely that individual differences exist" (p.753). As evidence increasingly points to a plastic view of learning, the manner that learning happens within an educational setting needs to adapt as well. Often curricula continues to rely on antiquated views that are heavily imbedded with a static understanding of learning that contrastingly has been seen to be a dynamic process. Perceiving learning, and language learning in particular, as a dynamic system Optiz (2012) describes language development as able to be

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A Dynamic Viewpoint Cillessen 15 molded by "interrelated networks of social interaction, experience and cognitive processes'" (p.702). Relationally then, what can seem like "unrelated linguistic phenomena" (p. 702) can actually be housed within one theoretical approach. Theories such as dynamic systems theory (DST), which is distinguished as being adaptive, complex, and in constant flux, allows for a non linear view of language to be explored. Seeing the int erconnection between environment and the nonlinearity interaction within the linguistic system begs for further adaptations to be explored within educational systems. Conclusion In this exploration of the changes in neuroanatomy in response to the presence of two linguistic communities and the possible corresponding plasticity hosted within the cognitive processes we have seen arguments from various sources. Initially we see from PulvermŸller et al. (2012) that correlational learning is essential i n the acquisition of language. Ghasemi & Hashemi (2011) demonstrated how this process is essential in L1 acquisition. The structural changes to these pathways have been highlighted by several of the studies. While childhood bilinguals can demonstrate this response in thickening and thinning cortical thickness within the left and right IFG. Adult bilinguals tend to show growth of GM in the MFG as well as STG. These areas are related to executive control function. Seeing this relation is especially of inter est when we examine the location of WMG later in life and see that there is a high correlation between e xecutive dysfunction, GM atrophy in regions of the STG. While other challenging cognitive activities have been explored and shown to affect this WMG and slow the onset of AD, language learning is a challenging cognitive

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A Dynamic Viewpoint Cillessen 16 activity that can continue well into the later years of life. Acquisition of a L2 in adulthood may cause a sense of panic in contrast to the implicit nature of learning that was most likel y experienced with the L1. Yet this panic has been shown to be necessary since even adults can learn implicitly, and in conjunction with the higher cognitive function that has developed, build their proficiency. Gaining further understanding of the plast ic nature of our neuroanatomy and the adaptation that has been demonstrated both in response to language learning, aging, and educational stimuli, as well as the bridges between these areas can continue to mold the manner in which both educators and learne rs approach learning. As the cognitive process of learning and the possible long term effects that bilingualism can have are explored, examining these processes as dynamic is essential if we are to understand the extent of learning process flexibility. ! ! !

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A Dynamic Viewpoint Cillessen 17 ! ! Appendix Definition of key terms: Bilingual The term bilingual has long been used when we are discussing two or more languages (Cenoz, 2013). Yet, the dispute comes into play when we consider whether the degree of use of the two language s is necessary of accounting or not. For example, a person may understand two separate languages, but does not use one of the two very often. This in turn can affect the proficiency with which they can maneuver the language. According to Grosjean (2010) b ilinguals can be defined as "those who use two or more languages (or dialects) in their everyday lives." Yet according to Li, as quoted in Cenoz (2013), "anyone who can communicate in more than one language, be it active (through speaking and writing) or p assive (through listening and reading)" (p. 5) is considered to be bilingual. Thus, Grosjean is in favor of use and Li is in favor of proficiency. There are disadvantages and

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A Dynamic Viewpoint Cillessen 18 advantages to both viewpoints. With Grosjean the question of what constitutes use is left to the wayside, while with Li the question of what constitutes communication and what constitutes language is left without answer. A conjoined representation of both is what we will use for the purposes of our examination. Therefore being biling ual refers to an individual that communicates in at least two languages (or dialects) via either active or passive use in their regular life. Maintaining this balanced view of bilingualism will allow us to view current studies in a holistic manner. Fig ures: Figure 1

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A Dynamic Viewpoint Cillessen 19 ! ! ! !

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A Dynamic Viewpoint Cillessen 20 Figu re 2

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A Dynamic Viewpoint Cillessen 21 Figure 3 ! ! ! ! !

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A Dynamic Viewpoint Cillessen 22 Figure 4 Middle Frontal Gyrus Inferior Frontal Gyrus Superior Temporal Gyrus

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A Dynamic Viewpoint Cillessen 23 Figure 5

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A Dynamic Viewpoint Cillessen 24 References Bialystok, E., Craik, F., & Luk, G. (2012). Bilingualism: Consequences for mind and brain. Trends in Cognitive Sciences, 16 (4), 240 250. doi:10.1016/j.tics.2012.03.001 Byrnes, J. (2008). Cognitive development and learning in instructional contexts (3rd ed.). Boston, Massachusetts: Pearson Education. Cenoz, J. (2013). Defining Multilingualism. Annual Review of Applied Linguistics, 33 3 18. doi:10.1017/S026719051300007X Dubinsky, J., Roehrig, G., & Varma, S. (2013). Infusing Neuroscience Into Teacher Professional Development. Educa tional Researcher, 42 (6), 317 329. doi:10.3102/0013189X13499403 Elbert, T., & Rockstroh, B. (2004). Reorganization of Human Cerebral Cortex: The Range of Changes Following Use and Injury. The Neuroscientist, 10 (2), 129 141. doi:10.1177/1073858403262111

PAGE 26

A Dynamic Viewpoint Cillessen 25 F romkin, V., Rodman, R., & Hyams, N. (2013). An introduction to language (10th ed.). New York, New York: Wadsworth Publishing. Ghasemi, B., & Hashemi, M. (2011). Foreign Language Learning During Childhood. Procedia Social and Behavioral Sciences, 28 872 876. doi:10.1016/j.sbspro.2011.11.160 Grosjean, F. (2010). Bilingual life and reality Cambridge, Massachusetts: Harvard University Press. Higby,, E., Jungna, K., & Obler, L. (2013). Multilingualism and the Brain. Annual Review of Applied Linguistics, 33 68 101. doi:10.1017/S0267190513000081 Klein, D., Mok, K., Chen, J., & Watkins, K. (2014). Age of language learning shapes brain structure: A cortical thickness study of bilingual and monolingual individuals. Brain and Language, 131 20 24. http://dx.doi.org/10.1016/j.bandl.2013.05.014 Liu, H., Fan, N., Rossi, S., Yao, P., & Chen, B. (2015). The effect of cognitive flexibility on task switching and language switching. International Journal o f Bilingualism, 1 17. doi:10.1177/1367006915572400 Luk‡cs, & KemŽny, F. (2015). Development of Different Forms of Skill Learning Throughout the Lifespan. Cognitive Science A Multidisciplinary Journal, 39 (2), 383 404.

PAGE 27

A Dynamic Viewpoint Cillessen 26 doi:10.1111/cogs.12143 McAvoy, M., Mitra, A., Coalson, R., D'avossa, G., Keidel, J., Petersen, S., & Raichle, M. (2015). Unmasking Language Lateralization in Human Brain Intrinsic Activity. Cerebral Cortex, 1 14. doi:10.1093/cercor/bhv007 Mitchell, M., Shaughnessy, L., Shirk, S., Yang, F., & Atri, A. (2012). Neuropsychological Test Performance and Cognitive Reserve in Healthy Aging and the Alzheimer's Disease Spectrum: A Theoretically Driven Factor Analysis. Journal of the International Neuropsychological Society, 18 1071 1080. doi:10.1017 /S1355617712000859 M Œ rtensson, J., Eriksson, J., Bodammer, N., Lindgren, M., Johansson, M., Nyberg, L., & L š vd Žn, M. (2012). Growth of language related brain areas after foreign language learning. NeuroImage, 63 240 244. doi:10.1016/j.neuroimage.2012.06.043 Plante, E., Almryde, K., Patterson, D., Vance, C., & Asbj rnsen, A. (2015). Language lateralization shifts with learning by adults. Laterality: Asymmetries of Body, Brain and Cognition, 20 (3), 306 325. doi:10.1080/1357 650X.2014.963597 PulvermŸller, F. (2012). Meaning and the brain: The neurosemantics of referential, interactive, and combinatorial knowledge. Journal of Neurolinguistics, 25 (5), 423 459. doi:10.1016/j.jneuroling.2011.03.004

PAGE 28

A Dynamic Viewpoint Cillessen 27 Raji, C., Lopez, O., Kuller, L ., Carmichael, O., Longstreth, W., Gach, H., Becker, J. (2012). White matter lesions and brain gray matter volume in cognitively normal elders. Neurobiology of Aging, 33 (4), 834.e7 834.e16. doi:10.1016/j.neurobiolaging.2011.08.010 Smits, M., Visch B rink, E., Sandt Koenderman, M., & Lugt, A. (2012). Advanced Magnetic Resonance Neuroimaging of Language Function Recovery After Aphasic Stroke: A Technical Review. Archives of Physical Medicine and Rehabilitation, 93 (1), S4 S14. doi:10.1016/j.apmr.2011.02. 023 Stein, M., Federspiel, A., Koenig, T., Wirth, M., Strik, W., Wiest, R., Dierks, T. (2012). Structural plasticity in the language system related to increased second language proficiency. Cortex, 48 (4), 458 465. doi:10.1016/j.cortex.2010.10.007 S tocco, A., Yamasaki, B., Natalenko, R., & Prat, C. (2014). Bilingual brain training: A neurobiological framework of how bilingual experience improves executive function. International Journal of Bilingualism, 18 (1), 67 92. doi:10.1177/1367006912456617 Tho mpson, C. (2000). NEUROPLASTICITY: EVIDENCE FROM APHASIA. Journal of Communication Disorders, 33 (4), 357 366. doi:10.1016/S0021 9924(00)00031 9

PAGE 29

A Dynamic Viewpoint Cillessen 28 Valian, V. (2015). Bilingualism and cognition. Bilingualism: Language and Cognition, 18 (1), 3 24. doi:10.1017/S1366728914000522 Vinogradov, S., Fisher, M., & Villers Sidani, E. (2012). Cognitive Training for Impaired Neural Systems in Neuropsychiatric Illness. Neuropsychopharmacology, 37 (1), 43 76. doi:10.1038/npp.2011.251 Wei, M., Joshi, A., Zhang, M., Mei, L., Manis, F., He, Q., Lu, Z. (2015). How age of acquisition influences brain architecture in bilinguals. Journal of Neurolinguistics, 36 35 55. doi:dx.doi.org/10.1016/j.jneuroling.2015.05.001 Woumans, E., Santens, P., Sieben, A., Versijpt J., Stevens, M., & Duyck, W. (2015). Bilingualism delays clinical manifestation of Alzheimer's disease. Bilingualism: Language and Cognition, 568 574. doi::10.1017/S136672891400087X