The human mind is a complex phenomenon, which continues to be investigated through neuroscience in great detail (Bassett & Gazzaniga, 2011). The structure of the brain is an intricate temporal and spatial multiscale, which composes molecular, cellular and neural phenomena, which together produce the physical and biological base for cognition (Bassett & Gazzaniga, 2011). Furthermore, each structure is organized into modules, such as anatomical or functional cortical areas, which form the foundation for cognitive functions that are adaptable to any commotions in the external environment (Bassett & Gazzaniga, 2011).
Much study has gone into behavioural science regarding the manner in which the nervous system can change its organization and eventually, its functions throughout an individual’s lifetime, an ability which is referred to as plasticity (Kolb, Gibb & Robinson, 2003). The functional and physical change in response to an environmental stimulus, behavioural experience or cognitive demand allow us to recognize the exceptional plasticity the brain has (Li, Legault & Litcofsky, 2014). Consequently, brain plasticity is of considerable interest, as it allows us to understand its sensitivity to experience, as well as the development of the brain and its behaviour to a new learning (Kolb et al., 2003). On the whole, experience can change the brains plasticity, in both the structure and the function (Osterhout et al., 2008). Like many other experiences, such as riding a bike or doing mathematics, the experience of learning a second language will induce changes in the brain (Osterhout et al., 2008).
Humans have a unique ability to learn more than one language and this is a skill which is considered a favourable asset, both educationally and cognitively (Osterhout et al., 2008). Today, more than half of the world’s population are learning a second language which came about as a result of globalisation, cross- cultural communication, increase in popular culture or simply, for requirements in a job (Li, Legault & Litcofsky, 2014). This experience will have an impact on the human brain, which has been proven by cognitive and brain studies, along with studies of memory, perception and attention (Abutalebi & Green 2007; Li et al., 2014; Mechelli et al., 2004). Through my own previous study with bilingualism, I believe that changes will occur in the mind or brain as a result of a second language learning. Subsequently, this paper will explore the neuroplasticity in second language learning with discussing changes in the electrophysiology response, brain sources and the brain structure.
The electrophysiological changes in the brain during L2 acquisition demonstrate the qualitative changes in the neural substrates of L2 learning, that can be recorded using the event- related brain potentials (ERPs) (Osterhout et al., 2008). The ERPs can reflect synchronized postsynaptic activity in cortical pyramidal neurons, which can, subsequently, be used to support the neural changes second language learning can induce in the brain and show new insights into L2 learning.
A large body of research has been conducted on the electrophysiological changes in the brain during L2 acquisition, including that of McLaughlin, Osterhout & Kim (2004). They examined the rate at which L2 is integrated into the learner’s language comprehension through recording their ERPs while they read or listen to L2 phrases. Their findings suggested that there are separate semantic and syntactic processes in a L2 learning context, with a presence of negative waves at 400ms and positive waves at 500ms (McLaughlin et al., 2004). These findings suggest distinct temporal properties as well as a developing linguistic competence of second language learners, which is evident through scalp recordings of the brains electrical activity. (McLaughlin et al., 2004).
Furthermore, grammaticalization during L2 learning is also assessed, where the acquisition of grammatical features and their morphological rules are examined. Osterhout et al., (2008) investigated 14 novice French learners who were required to read 30 sentences and recorded them using EEG. Their results showed a N400 effect which was replaced by N600 after 4 months of learning (Osterhout et al., 2008). As a result, it can be concluded that the brain will produce a striking difference in electrophysiological activity after consistent L2 learning, which can be evident through ERP and EEG recordings. These findings can be further supported by White, Genesee & Steinhauer (2012), who investigated Korean- Chinese late L2 learners of English. Using ERPs, their findings showed significant P600 after the end of instruction which came about as a result of online grammaticality judgement task and behavioural responses (White et al., 2012).
Overall, these studies lead us to infer that the neuro- cognitive processes underlying in the brain will be modified through second language learning and electrophysiological changes in the brain will occur during the learning of a second or foreign language, which is supported by a range of cognitive and brain studies.
Many researchers today have investigated how the brain supports more than one language (Liu & Cao, 2016). Brain sources refers to the neural sources of the language- effect ERP effects, which allow to convey the changes in the current density and which areas of the brain are activated during second language learning (Osterhout et al., 2008). Measuring the brain source can reflect the changes in the source distribution, as a result of the processing of the second language (Osterhout et al., 2008). The brains source is measured simultaneously with ERPs to determine the distribution and which brain area is activated.
Due to the advancements in technology, superior temporal resolution and reduced spatial resolution can be measured through tomographic analysis analogous, provided by neuroimaging methods (Osterhout et al., 2008). In a study by Osterhout et al., (2008), a low-resolution electromagnetic tomography (LORETA) was used to measure the sources associated with processing sentences in L1 and L2. As a result, it is demonstrated that the L1 distributions were in the posterior parts of the brain, including the temporoparietal and extrastriate regions. The L2, on the other hand, has the greatest current in the medial dorsal frontal lobe. Furthermore, it has been suggested that bilinguals will have distinct advantages when it comes to cognitive control, which leads to better executive functions such as inhibiting, updating and switching. Previous studies, such as Bialystok (2009) and Mechelli (2004) have found an increase in neural activities in several cognitive controlled areas in the brain, which form an integrated network for bilingual control (Bialystok, 2009). This, subsequently, results in better conflict monitoring abilities and attention.
In general, L2 processing involves more regions than L1 (Liu & Cao, 2016), and the processing is particularly more demanding in late bilinguals. The proficiency in L2 is a major factor in determining the peak and extent of activations in the brain, along with the neurophysiological mechanisms, as a function of learning (Kotz, 2009). However, in general, L2 has a more widespread cortical activity, as it is described as less automated and more effortful, thus, more brain activity (Wattendorf & Festman, 2008). Subsequently, the brain activation or distribution will change as we learn a second language and it will be highly influenced by the age of acquisition of L2.
The points discussed above have explored the specific brain function patterns when learning a second language, but moreover, these neural changes are often followed by anatomical changes in the brain structure (Li et al., 2014). Second language learning can influence changes in the brains grey matter, white matter and cortical thickness (Li et al., 2014; Mechelli et al., 2004).
The brain is the most complex organ in the human organ which is highly adaptable to bilingualism and multiple language experiences, that responds both functionally and structurally to any brain changes (Li et al., 2014). Today, the changes in the brain structure in response to L2 learning can be measured precisely through neuroimaging methods, such as fMRI (Li et al., 2014). In terms of the organizing principles of the brain, both grey matter and white matter are made of neurons, in which grey matter mostly consists of neuronal cell bodies, while white matter consists of axons and support cells (Li et al., 2014). Cortical thickness refers to the thickness of the grey matter, which is primarily a direct measure of cortical morphology (Li et al., 2014).
Subsequently, studies have found that bilinguals would have a greater grey matter density in the left inferior parietal lobule than monolinguals (Li et al., 2014; Mechelli et al., 2004). This measurement, however, is highly influenced by the age of acquisition of the second language, as Li et al. (2014), has shown that the effect was greater in early bilinguals compared to late bilinguals. Other studies such as Mechelli et al. (2004) have also found that bilinguals had a greater density in the left inferior parietal cortex, compared to monolingual speakers and it is more pronounced in early bilinguals. The changes in the grey matter density suggest a change in cell size when learning a second language, which often involves both neurons and glial cells (Li et al., 2014, Mechelli et al., 2004).
The white matter integrity can further be used to assess the anatomical changes in the brain in response to second language learning (Li et al., 2014). This is because second language learning can modify white matter integrity quite early on in the experience, where several areas of the brain showed a greater white matter density in bilinguals (Mechelli et al., 2004). The cortical thickness and grey matter share an inverse relationship (Li et al., 2014), due to the cortical folding patterns. As previously mentioned, the grey matter volume changes in response to bilingual experience and the white matter density also differs between monolinguals and bilinguals, however, the cortical thickness correlates with the learners age of acquisition for L2 (Li et al., 2014). Hence, a later learning of L2 is equivalent to a greater cortical thickness (Li et al., 2014).
Taking these points into consideration, second language learning will stimulate changes in the brains structure, which can be observed through the changes in grey matter and white matter densities, as well as the cortical thickness.
In conclusion, the brain will change in response to second language learning, which can be seen through electrophysiological changes, changes in brain sources and changes in the brains structure. The electrophysiological changes demonstrate the qualitative changes in the neural substrates of L2 learning. Furthermore, the changes in brain sources describe the changes in the current density and which areas of the brain are activated during second language learning. Second language learning will also induce anatomical changes in the brains structure.
The study of neuroplasticity has become a growing interest among researchers, particularly due to the ability of the human brain to adapt in response to environmental stimulus, cognitive demand or behavioural experience (Li et al., 2014). An individual’s linguistic experience has led to significant findings regarding the changes in the brain and how it adapts itself with the introduction of a new language. Moreover, each research article has also emphasized the importance of age of acquisition, proficiency or performance level, language specific characteristics, individual differences as well as other environmental properties which greatly influence the type and extent of change in the brain during second language learning.
Future studies should consider more systematic investigations into the complex function- structure interactions. Through reviewing a number of research articles and their studies on plasticity, most neuroimaging and their correlations were opaque, without any clear reasons as to why the results are sometimes positive or negative. Also, a number of studies have called out for a more definite analysis to identify the cellular and molecular mechanisms underlying language- related changes in the brain (Li et al, 2014; Osterhout et al., 2008; Mechelli et al., 2004; Abutalebi & Green 2007)
This paper has discussed how neural and structural plasticity occurs as a result of second language learning, which is supported by several empirical findings. Therefore, it is appropriate to say that the linguistic brain is very plastic, where second language learning can induce electrophysiological, distributional and structural changes.
References
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