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A Review on Brain Mechanisms for Language Acquisition and Comprehension, Summaries of Psychology

:Language Acquisition, Language Comprehension, Cognition, GLM, ICA, PCA, ERP, t-test, z-score.

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A Review on Brain Mechanisms for Language Acquisition and
Comprehension
Kailash Nath Tripathi1, Anand Bihari2, Sudhakar Tripathi3, Ravi Bhushan Mishra4
1Merrut Institute of Technology, Merrut, 2Vellore Institute of Technology, Vellore, 3R. E. C. Ambedkar Nagar,
U. P. 4IIT (BHU) Varanasi
1
Abstract:
This paper aims to bring the main viewpoint of language acquisition and language comprehension. In language
acquisition, we have reviewed the different types of language acquisitions like first, second, sign and skill
acquisition. The experimental techniques for neurolinguistic acquisition detection is also discussed. The findings
of experiments for acquisition detection is also discussed, it includes the region of brain activated after
acquisition. Findings shows that the different types of acquisition involve different regions of the brain. In
language comprehension, native language comprehension and bilingual’s comprehension has been considered.
Comprehension involve different brain regions for different sentence or word comprehension depending upon
their semantic and syntax. The different fMRI/EEG analysis techniques (statistical/ graph theoretical) are also
discoursed in our review.Tools for neurolinguistic computations (pre-processing/computations/analysis) are
alsodiscussed.
Keywords:Language Acquisition, Language Comprehension, Cognition, GLM, ICA, PCA, ERP, t-test, z-score.
1 Introduction
The past several years has yielded an enormous research work in neuroscience investigating language
acquisition, comprehension and production. Non-invasive, safe functional brain measurements have now been
proven feasible for use with infants or adult for neural data acquisition. The neural signature of effect of learning
at the phonetic level can be recognized at a amazingly high precision. Continuity in linguistic development,
brain responses to even phonetic level stimuli can be observed with theoretical and clinical impact.
2Language Acquisitions
Human brain the command centre controls heart rhythm, memory and language to all human activities. Broca’s
area a small region in inferior frontal gyrus(IFG) necessary for production and coordination of language is found
in left hemisphere in most of people. Wernicke’s area the counter part of Broca’s area in superior temporal
gyrus(STG) performs language comprehension both written and spoken. The area of Broca’s area is
usually described as composed of the cytoarchitecturally defined area of Brodmann BA44, the pars opercularis
and BA 45, and the pars triangularis.The cytoarchitecturally identified region BA 22 covers the latter two-thirds
of the lateral convexity of the STG and is part of the Wernicke region.[1]
Figure 1: Langauge area in human brain comprises Broca’s and Wernicke’s Area
The acquisition of languages is one of the most important human traits and certainly it is the brain that
undergoes the changes in development. Therefore the root of grammatical rules should be ascribed to an
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A Review on Brain Mechanisms for Language Acquisition and

Comprehension

Kailash Nath Tripathi

1

, Anand Bihari

2

, Sudhakar Tripathi

3

, Ravi Bhushan Mishra

4

1 Merrut Institute of Technology, Merrut, 2 Vellore Institute of Technology, Vellore, 3 R. E. C. Ambedkar Nagar,

U. P. 4 IIT (BHU) Varanasi

1

Abstract:

This paper aims to bring the main viewpoint of language acquisition and language comprehension. In language

acquisition, we have reviewed the different types of language acquisitions like first, second, sign and skill

acquisition. The experimental techniques for neurolinguistic acquisition detection is also discussed. The findings

of experiments for acquisition detection is also discussed, it includes the region of brain activated after

acquisition. Findings shows that the different types of acquisition involve different regions of the brain. In

language comprehension, native language comprehension and bilingual’s comprehension has been considered.

Comprehension involve different brain regions for different sentence or word comprehension depending upon

their semantic and syntax. The different fMRI/EEG analysis techniques (statistical/ graph theoretical) are also

discoursed in our review.Tools for neurolinguistic computations (pre-processing/computations/analysis) are

alsodiscussed.

Keywords: Language Acquisition, Language Comprehension, Cognition, GLM, ICA, PCA, ERP, t-test, z-score.

1 Introduction

The past several years has yielded an enormous research work in neuroscience investigating language

acquisition, comprehension and production. Non-invasive, safe functional brain measurements have now been

proven feasible for use with infants or adult for neural data acquisition. The neural signature of effect of learning

at the phonetic level can be recognized at a amazingly high precision. Continuity in linguistic development,

brain responses to even phonetic level stimuli can be observed with theoretical and clinical impact.

2Language Acquisitions

Human brain the command centre controls heart rhythm, memory and language to all human activities. Broca’s

area a small region in inferior frontal gyrus(IFG) necessary for production and coordination of language is found

in left hemisphere in most of people. Wernicke’s area the counter part of Broca’s area in superior temporal

gyrus(STG) performs language comprehension both written and spoken. The area of Broca’s area is

usually described as composed of the cytoarchitecturally defined area of Brodmann BA44, the pars opercularis

and BA 45, and the pars triangularis.The cytoarchitecturally identified region BA 22 covers the latter two-thirds

of the lateral convexity of the STG and is part of the Wernicke region.[1]

Figure 1: Langauge area in human brain comprises Broca’s and Wernicke’s Area

The acquisition of languages is one of the most important human traits and certainly it is the brain that

undergoes the changes in development. Therefore the root of grammatical rules should be ascribed to an

implicit process in the human brain. Linguists find speaking, signing and understanding language to be the key

language skills, i.e. natural or inborn and biologically determined, while they find reading and writing to be

secondary. In truth, acquisition of a native or first language (L1) through these primary faculties during the first

years of life, whereas children learn their linguistic knowledge gradually. Speech in children progresses from

babbling at around the age of 6-8 months, to the single-word stage at 10 to 12 months, and then to the two-word

stage at around 2 years. There is a profound difference between linguistic factors between L1 and L2. An

L2(Second Language) can be learned at any moment in life, although the L2 capacity is rarely comparable to

that of L1 if it is acquired after the predicted 'sensitive period’ from early childhood to puberty (È12 years of

age). Numerous studies of functional magnetic resonance imaging(fMRI) and positron emission tomography

(PET) have shown that auditory phonological processing is correlated with activation in the posterior superior

temporal gyrus (STG) [Brodmann's region (BA) 22], while lexico-semantic processing is typically associated

with activation in the left extra-Sylvian temporoparietal regions, including the angular ones [2].

In [3], Eric Lenneberg (1967) proposed that the acquisition of human language was an example of biologically

limited learning, he stated that a child would have biological heritable component to learn language. He

concluded that the process of acquiring langauge is profoundly ingrained and, species-specific, human

biological property. Any language usually acquired during a crucial time beginning early in life and ending in

puberty. He indicated that language could only be learned with difficulty or through a different learning method

beyond this time.

A critical period is a time of maturation during which some of the key stimuli would have their peak impact on

development or learning, resulting in normal actions adapted to the specific environment to which the organism

was exposed. If the organism is not subjected to this phenomenon until after this period of time, the same

phenomenon may have either a diminished effect, or may have no effect at all in extreme cases. Studies show a

close association between age of language use and the ultimate degree of competency (PL) attained. However,

exposure age does not affect all aspects of language leaning equally. Therefore, the crucial effects of the critical

period seem to focus on phonology, morphology, syntax and not meaning processing [4].

The existence of critical, or at least a sensitive period for language acquisition in human being is explained by

an evolutionary model suggested by J. R. Hurford in [5].

The acquisition of first language is one of the unexplained mysteries which surround us in our daily lives. A

child learns language spontaneously, almost miraculously, as its learning of language progresses rapidly with an

obvious pace and accuracy. Most children quickly learn language, giving the illusion that the process of

acquiring first language is easy and straightforward. This is not the case, however, as children go through many

stages of first language acquisition .The stages of language learning in children usually consist of: cooing,

babbling, holophrastic stage, telegraphic speech and normal speech. The age of cooing is up-to 9 months till

then children use phonemes from every language. At 9 month they start babbling in which they selectively use

phonemes from their native language. At the age of 12 month they start using single words. When they are in

holophrastic stage at around 18-24 months, they can combine words in two words stages.By the age of around

30 months they develop to the telegraphic stage where they can utter a clear phrase structure. As the children

develop physically, so does their language skills as they internalize more complex systems by widening their

vocabulary and their immediate surroundings. At the age of 5 years children reached up to normal developed

speech.

There are three famous theories for first language acquisition: the behaviourist theory, the innatist theory and

interactionists theory. Behaviourist theory[7] equated learning to a language all behaviour are acquired through

interaction with environment and interactions are imitation, reinforcement, practice and habit formation.

Children learn their first language by stimuli and children's responses are influenced by reinforcement.

The Innatist theory[8] believed that children are equipped with a device called the language acquisition device

(LAD) and universal grammar (UG) which accounts for the swift mastery of language among children despite

the extremely abstract nature of language. The Interactionists[9] believes that language is not a separate element

of the mind as language reflects the information gained through children's physical contact with the world.

Authors in [30] found that the existence of feedback had a significant impact on the structure of the network

used by learners to learn the properties of words in a natural language. A statistical learning system suggests that

learners track distributional information in their environment and use that information to derive the structure and

concepts they obtain about the sensory inputs. For example, in running speech, infants can segment words from

an artificial language by monitoring the transitional probability of syllables.

2.2 Second Language Acquisition

Acquisition of their vocabulary is a crucial part of learning a new language. Morphology in the linguistic sense

is the study of words, how they are created, and how they relate to other words in the same language. Study in

[31] discussed the neural signature in initial phase of morphological rule based learning of a novel language

(L2) in adults and suggests that even after a short exposure, adult language learners can acquire both novel

words and novel morphological rules of L2.

Bilingualism studies have identified ways in which a second language's neural representation (L2) varies from

that of the first language (L1) of an person[32]. In particular, there are many variations in activation between L

and L1, both in degree and magnitude. L2s tend not only to display more activity within traditional language

areas of the left hemisphere but also to enable more regions beyond the traditional language network. There are

two prevailing hypotheses about why L2 neural signatures vary from L1 signatures. The first is that, during L

learning, these variations reflect decreased neuroplasticity that occurs at a later age than learning with L1. L

learning needs increased neural capital on this account due to maturational changes in neural plasticity within

regions and pathways that enable first language learning [33]. The alternative hypothesis is that neural variations

in L1 versus L2 are caused instead by the fact that the L2 of individuals is typically lower in ability than their

L1. Therefore, the processing of L2 requires increased computational requirements and thus increased neural

resources[34]. The experimental results indicate that ability and AoA describe different functional and structural

networks within the bilingual brain, which we interpret as indicating distinct plasticity forms for age-dependent

effects versus experience and/or skills.

Authors in [35] consider structural changes to brain areas believed to support language roles during learning of a

foreign language. Experimental findings show that the volume of the hippocampus and the cortical thickness of

the left middle frontal gyrus, inferior frontal gyrus and superior temporal gyrus increase for interpreters

compared to controls. In interpreters with higher foreign language abilities, the right hippocampus and the left

superior temporal gyrus were both structurally more maleable[36].

Study in[37] investigated how the age at which L2 was acquired influenced brain structures in bilingual people.

This shows that AoA, language skills and current exposure rates are equally important in taking into account the

systemic differences. Structural changes related to bilingualism and multilingualism have also been reported,

bilinguals tend to have increased grey matter volume/density in Heschl’s gyrus [38], the left caudate [39] and

the left inferior parietal structure [40].

Authors in [41] explored the correlation between instructed second language acquisition (ISLA) skills and

identified a clear connection between attitude towards language learning and second language skills. The

analysis of language learning achievements in monozygotic and dizygotic twins [42] point to the possibility that

having a positive attitude towards language learning and the language class is related to how well students do in

ISLA independent of natural language abilities, teacher skill and L1-L2 relations.

In [43], authors examined the neural substrates of novel grammar learning in a group of healthy adults

conducted an experiment and study based on fMRI that, in terms of functional connectivity, the involvement of

the brain network during grammar acquisition is coupled with one's language learning ability.

2.3 Sign Language Acquisition

Children born deaf can not understand the languages spoken around them, and there is inadequate phonetic

information provided by the visual signal of speech to facilitate spontaneous language acquisition. For many of

these youngsters, language learning continues far beyond infancy after exposure to and immersion in a sign

language at ages. Variation in the period of language acquisition in the adult brain influences language

processing[44], [45]. In the classical language areas of the left hemisphere LH, fMRI studies of deaf native

signers have find activation with a trend towards bilateral activation of the frontal and temporal lobes. These

findings were observed using different tasks and triggers for distinct sign language namely American, British

and Japanese[46]–[48].

The learning age is linearly and inversely related to activation rates in anterior language regions and positively

related to activation rates in subsequent visual regions for linguistic tasks of American sign language (ASL)

sentences, grammatical judgment and phonemic hand judgment [29].

2.4 Skill Acquisition

Authors in [49] addressed that the expression of this neuroplasticity depends on the age at which learning starts

in several domains of skill acquisition. In studies aimed at determining the relationship between age of maturity

and brain plasticity, the fact that most abilities are learned late in childhood or adulthood has proven to be a

limit. According to [50], early sensory experiences tend to have the greatest capacity to improve neuronal

circuitry in the early years of development, When the brain is in active building up phase. Neuroimaging studies

of language development concentrate on the variations between simultaneous and concurrent bilinguals in brain

structure and function, and whether bilingualism is accomplished later in life. It also discusses the idea of an

optimal time in the production of languages and thus gives the relationship between the acquisition era and the

ultimate results[51].

Santiago Ramon Y Cajal (Nobel prize winner) in 1894, proposed that mental activity might induced

morphological changes in brain structure. Authors in[52] determined that the human brain structure expands and

get renormalized during skill acquisition. It is known as the expansion-renormalization model, according to

which neural processes related to learning always adopt a sequence of expansion, selection, and renormalisation.

[53]. The model foretell an initial increase in the density of grey matter, theoretically representing the growth of

neural capital such as neurons, synapses and glial cells, Accompanied by a selection process operating on this

new tissue which results in a complete or partial return to the baseline overall volume after selection has been

completed. To date, improvements in brain structure have been reported on different time scales, such as several

months of juggling training, medical examination study, space navigation training, learning of foreign

languages, etc.

For any language learning, the age of its acquisition matters a lot. The literature shows the importance

of age for learning a language, early language acquisition improves the probability of being proficient in a

language.For first language learning, social environment of infants also plays a significant role, age of learning,

nature of input language and teaching strategy is also important. Second language acquisition becomes easier if

it is learned in early age (before puberty)because during this period brain have more plasticity and it also have

lot of idea about language learning which is experienced during first language learning. Vocabulary and

grammar learning of second language is easier if it is done simultaneously or sequentially of L1 in early

childhood. Sign language acquisition is done in later age than infants, as it is generally learned by born deaf

children. Age of sign language learning also affects its proficiency. Skill development or expertise learning is

also depending on age and the language proficiency before getting that skill. Learning at later stage can be

improved by doing morphological learning.

Table 2: Review of Language acquisition in brain

S.N. Author Task Computation Method

Data Acquisition Method

Result

Language Acquisition

1 P. K. Kuhl et. al., 2010 [54]

Language and pre-reading in year two, third and fifth years.

Alpha, beta and gamma rhythms analysis.

EEG/ERPs/MEG/f MRI/NIRS

Early mastery of the phonetic units of language demands social learning.

2 R. I. Mayberry et. al., 2011[29]

American Sign Language, grammatical judgment and phonemic-hand judgment

t-statistics fMRI data The left lateralised activation pattern was observed

3 I. Kovelman et. al., 2012 [14]

Language task and Rhythm Task

t-test analysis functional Near Infrared (fNIRS) imaging

The right hemisphere overall displayed greater activation against the sluggish rhythmic stimulation, and the left hemisphere displayed greater activation compared to the quicker and slower frequencies.

4 J. Martensson et. al., 2012 [35]

Three months of intense foreign language studies

t-test on cortical thickness

MRI Structural changes in brain areas known for performing language roles during the learning of foreign languages. 5 S. Penicaud et. al., 2013 [28]

American Sign Language (ASL) voxel-based whole-brain correlational analysis.

fMRI Not only the functional but also the structural structure of the brain is impaired by lack of early language experience. 6 Miao Wei et. al., 2015 [37]

Language history questionnaire task

Cluster size, t- score.

MRI/fMRI/ PET In the right parietal cortex, earlier second-language sensitivity is correlated with greater volumes. Consistently, as AoA decreased, the cortical region of the right superior

considered essential to human language communication: the area of Wernicke and the area of Broca. The

accurate fasciculus is the brain region between the Wernicke region and the Broca area which connects the two

via bundles of nerve fibers. This part of the brain acts as a hub of transportation between the two areas mainly

concerned with speech and communication.

Comprehension of sentences depends crucially on deciding the thematic relationship between noun phrases, i.e.

defining who is doing what to whom. Study in [55] based on fMRI evaluated the relevant grammar and a key

factor underlying the assessed output in the verbal working memory. Voxel-based gray matter morphometry

showed that while the capacity of children to assign thematic roles in the left inferior temporal gyrus and the left

inferior frontal gyrus in positively correlated with gray matter likelihood (GMP). The verbal work memory-

related output in the left parietal operculum is positively associated with GMP extending into the posterior

superior temporal gyrus. Those areas are known to be involved in dynamic sentence processing in a particular

way. Results indicate a common GMP relationship in language-relevant brain regions and differential cognitive

abilities that direct their interpretation of the sentence.

EEG mu rhythms recorded at fronto-central electrodes are commonly considered to be measures of human

motor cortical activity as they are modulated when the participants perform an action, experience another's

action or even imagine an action. Study in [56] recorded the modulation of mu rhythms in time frequency (TF),

while participants interpreted the language of motion, abstract language and perceptive language. The findings

indicate that mu repression is correlated with the language of practice rather than with abstract and perceptive

language at fronto- locations. It also indicates that the activation takes place online through multiple words in

the sentence, based on semantic integration.

During sentence processing region of the left upper temporal sulcus, inferior frontal gyrus and left basal ganglia

show a systemic increase in brain activity as a function of constituent size, indicating their participation in

computing syntactic and semantic structures. Experiments in [57] for non-spoken sign language on deaf

participants show that the same network of language areas was found, while reading and sign language

processing created similar effects of the linguistic structure in the basal ganglia, the effect of structure in all

cortical language areas was greater for written language relative to sign language.

Based on evidence from neuroimaging, literature[58] reported both substantial overlap and unique linguistic

cortical activation between comprehension of the sign language and observation of gestural behavior. In the

upper / lower parietal lobe and the fusiform gyrus, overlaps in cortical activation are primarily observed.

Authors in[59]found that American Sign Language (ASL) stimulated more strongly the left inferior frontal

gyrus (IFG) and the middle superior temporal gyrus (STG) in deaf native signers than gestures expressing

roughly the same material. Here Graph Theoretical Analysis(GTA) is used on the neural dependent cognition

studies as an important complementary perspective to the activation research.

Study in [60] illustrates the semantic and grammatical processing of accented speech, both native and

international. Closer analysis of listeners who did not understand the foreign accent correctly indicated that

listeners who recognized the foreign accent displayed ERP responses for both grammatical and semantic errors.

By comparison, listeners who did not correctly recognize the foreign accent gave no ERP responses to the

foreign accented condition's grammatical errors, but displayed a late negativity to semantic errors.

Study in [61] indicates that mechanisms of the right hemisphere in the brain are essential to triggering elements

of event information that breach the linguistic meaning. The brain stimulates components of event-knowledge

that are semantically anomalous in context during learning.

In [62] authors propose that the prosodic information available during spoken language comprehension supports

the generation of online predictions for upcoming words, and that comprehension of spoken language during

serial visual presentation (SVP) reading, at least for quantifier sentences, may proceed more incrementally than

understanding. The analysis demonstrates that the comprehension of spoken sentence continues fully

incrementally, the results of truth meaning in both positive and negative quantifier sentences are alike. This also

suggests that people use the spoken language more effectively than written SVP feedback to produce online

predictions about coming words. During listening to natural speech, learning usually continues more

incrementally than during an ERP experiment with N400 results during SVP hearing.

Authors in [63] note that, during late childhood and adolescence, the cortical depiction of language

comprehension is added concentrated within the superior and middle temporal regions. Higher language ability

are correlated with greater right hemispheric engagement during the listening of stories. Language

comprehension is expressed more bilaterally than language output and a hemispheric dissociation with the

development of the left hemispheric language, but comprehension of the bilateral or right hemispheric language

is not uncommon even in healthy right handed subjects.

In [64], authors conducted an experiment and found that medial parietal lobe requires the production of

referential words. Analysis of the experiment based on fMRI is done using a pairwise t test of total cluster

activation which verified that each referential sub-condition was correlated with more activation than the non-

reference condition.

The prefrontal brain regions historically associated with language comprehension are the Wernicke area and the

Broca area.11 subjects of the Curtiss- Yamada Comprehensive Language Evaluation Receptive (CYCLE-R) are

taken to perform voxel based lesion symptom mapping (VLSM) based analysis of functional neuroimaging data

indicated that lesions to five left hemisphere brain regions affected performance on the CYCLE-R, including the

posterior middle temporal gyrus and underlying white matter, the anterior superior temporal gyrus, the superior

temporal sulcus and angular gyrus, mid frontal cortex in BA 46 and BA 47 of the inferior frontal gyrus. Analysis

also suggested that the middle temporal gyrus may be more important for comprehension at the word level,

while other regions may play a greater role at the level of the sentence.

3.1 Bilingualism: A large portion of the world's inhabitants is bilingual, and is flawlessly in over one language.

A bilingual speaker routinely produces and understands without difficulty sentences which belong to two (or

more) languages. Hence, knowing hoe two languages coexists in one brain with little disagreement or intrusion

in both codes is a theoretical and applied question of great interest. There is ongoing debate about whether early

and/or prolonged exposure to more than one language may lead to changes in patterns of brain activity during

language processing.

Authors in [65] performed an experiment involving highly qualified bilingual Spanish / Catalan and Spanish

monolinguals made grammatical and semantic decisions in Spanish while being tested for fMRI.Grammatical

judgement showed increased activation in IFG (BA 45), fusiform gyrus (BA37), occipital lobe (BA 18) and in

superior parietal lobe (SPL, BA 7). For monolingual group cortical activations were found in IFG (BA 45/46/9),

SFG (BA 6), BA 8/32and BA 18/23/37). Study indicates bilinguals are attracting new areas of the brain.

However, these different areas that depend on the learning age, language use, task circumstances, type of

stimulus, cognitive / linguistic demands, and possibly the characteristics and relative similarities between the

languages the bilingual speakers speak.

It has been shown that the two languages of Bilingual are simultaneously involved during listening, reading and

speaking, even when only one language is specifically required. This parallel activation was shown to promote

lexical access and to interfere in bilingual comprehension with the language processing. Research has shown

that when bilinguals process visual words, they experience co-activation of language, and use inhibitory

regulation to overcome non-target language competition. Authors in [66]suggest that the degree of language co-

activation in bilingual spoken word comprehension is modulated by the amount of regular exposure to non-

target language; and that bilinguals less affected by cross-language activation may also be more effective in

suppressing non-linguistic task intervention.

Findings in [67] showed that language processing can be considered as the result of a network of brain regions

interacting, rather than finding just a few brain areas to be involved in it. The experiment based on fMRI and its

interpretation showed the activation of BA 44 and BA45 to be left lateralized in the three tasks (receptive

semantic expressive paradigm), indicating roles in language phonology and semantic; however, their right

homologous areas were also involved, which may be due to their involvement in executive function, attention or

memory manipulation. On the contrary, BA 22 activation dominated at the right. The authors propose that right

BA22's contribution to language acquisition is an integral part of a broader chain comprising left IFG, bilateral

STG and lower parietal lobule. There are also studies that consider the right hemisphere as the seat for the

transmission of phonology and semance.

EEG-based studies in[68]have taken on two tasks: the semantic decision-making task and the task of reading.

The numerous experiment 1 wave maps indicate there was a frontal distribution of the disparity between literal

and novel metaphoric sentences. For both studies, the amplitudes of late positive complex (LPC) for novel

metaphoric sentences were decreased compared to those for anomalous sentences over parietal sites. While this

effect was clearly lateralized in experiment 2, in experiment 1 it posed a wider parietal distribution.

Authors in [69] performed an experiment focused on repeated transcranial magnetic stimulation (rTMS) taking

lexical decisions against basic tasks of judging. Findings provide evidence of an early motor cortex- TMS

intervention protocol creates a lateralized left, task and meaning contextual improvement in response latencies,

slowing down action-related word processing compared to faster abstract word reactions. The findings clearly

suggest causal involvement of different modality circuits in language understanding, suggesting that cognitive

phenomena of high order are based on simple biological mechanisms.

In [70], authors conducted a Near Infrared Spectroscopy (NIRS) experiment using the method of listening to

English sentences with six separate speeches. The findings showed that Japanese subjects had understood

speech with some of the characteristics of speech when amplitudes were expanded at certain frequency ranges.

The NIRS measurement also revealed that the enhancement of high frequency amplitudes ranging from 7000 to

8500 Hz increased concentration of Oxy-Hb in most language areas (BA 45/44/22).

Study in[71] shows that the neural representation of sentences in two languages is normal. From a mapping built

in English, the proposed model successfully predicted Portuguese sentences using brain positions and weights

applied to neutrally plausible semant features (NPSF). The mapping between the neural activation patterns and

analysis 7 R. Metusalem et. Al., 2016[61]

Expected, Event-Related, Event- Unrelated words and comprehension question answers are used

Several statistical analyses were conducted on mean ERP voltage measures

EEG Foster our understanding of the neural basis of event information activation and advance our understanding of how event awareness is activated in incremental understanding during creation of perceptions and elaborate inferences more generally. 8 D. Freunberger et. al., 2016[62]

N400 event-related potentials (ERP)

Linear Mixed Effects (LME) Models Using S Classes.

EEG People use the spoken language more effectively than written SVP feedback to produce online predictions of coming words. 9 Y. Yang et. al., 2017 [71]

English and Portuguese language reading

BOLD activation analysis

fMRI Proven ability to predict meta- language through cultures, people and bilingual status. 10 S. Grey et. al., 2017 [60]

Foreign-accented and native- accented speech

Mean ERP amplitudes

EEG/ERP Provide novel insights into understanding the impact of listener familiarity and foreign-emphasized speaker status on language processing neural correlates. 11 L. Liu et.al., 2017 [58]

Learning sign language by signers and Non-signers 'understanding of sign language.

Graph theoretical analysis (GTA)

fMRI When observing sign language, the hearing signers and non-signers showed identical cortical activations. The frequently activated network was structured differently between the two classes, however. 12 C. Brodbeck et. al., 2017[77]

Visuo-spatial referential Domains t-tests MEG/EEG Reports the medial parietal lobe participates in the production of referential words. 13 P. Chen et. al., 2017 [66]

Word pairs consisting of an English-Korean inter-lingual homophone

ANOVAs with relatedness

Event-related potential (ERP)

The amount of regular exposure to the non-target language modulates the degree of language co-activation in bilingual spoken word comprehension. 14 N. Vukovic et. al., 2017 [78]

Action words, abstract words and pseudo words

ANOVA, with the independent factors of Task

repetitive transcranial magnetic stimulation (rTMS)

Cortical motor regions play a vital role in understanding language.

15 K. Inada et. al., 2017 [70]

English speech task Enhanced amplitudes

Near-infrared spectroscopy system (NIRS)

English discourses with enhanced amplitudes within a certain frequency range can affect brain function activation in the language processing area and contribute to a better understanding of English speaking. 16 A. Moreno et.al., 2018 [57]

Sign language paradigm and written French stimuli

Z-score MRI/fMRI It suggests that the language network is systematically active in combinatorial language operations, comprising the left superior temporal sulcus, inferior frontal gyrus, and basal ganglia. 17 R. Alemi et. al., 2018 [67]

Word Production (WP) task, Auditory Responsive Naming (ARN) paradigm, Visual Semantic Decision (VSD) paradigm

Group ICA fMRI The language function should be regarded as the result of a network of brain regions collaborating.

18 K. Rataj et. al., 2018 [68]

Semantic decision and a reading task

t-test EEG The Late-Positive-Complex (LPC) pattern is modulated by both conventionality and task demand.

4Data Acquisition and Analysis Techniques

4.1 Data Acquisition

Over the last decade has shaped rapid developments in non-invasive practices that observe language processing

in human brain. They include Electroencephalography (EEG)/ Event-related Potentials (ERPs),

Magnetoencephalography (MEG), structural/resting-state Magnetic Resonance Imaging (rsMRI), functional

Magnetic Resonance Imaging (fMRI), Near Infrared Spectroscopy (NIRS), Diffusion Tensor Imaging (DTI),

Positron emission tomography (PET) etc.

4.1.1 Magnetic resonance imaging (MRI) can be paired with MEG and/or EEG, which offers static structural /

anatomical brain images. Structural MRIs display structural variations over the lifetime of brain regions and

they were recently used to predict second-language phonetic learning for adults. Magnetic resonance imaging

(MRI) can be paired with MEG and/or EEG, which offers static structural / anatomical brain images. Structural

MRIs display structural variations over the lifetime of brain regions and have recently been used to predict

phonetic learning of the second language of adults.[79]. In young children, structural MRI tests recognize the

size of different brain structures and these tests have been shown to be linked to language skills later in

childhood. When structural MRI images are superimposed on the physiological activity observed by MEG or

EEG, it is possible to enhance the spatial localization of brain activity reported by those methods. [80].

4.1.2 Functional magnetic resonance imaging (fMRI) is a common tool for human neuroimaging, since it

offers high spatial resolution maps of neural activity across the entire brain. [81]. The fMRI senses changes in

bloodoxygenation that happen in the neural activation response. Neural effects occur in milliseconds; but the

changes in bloodoxygenation they cause extend over many seconds, greatly restricting the temporal resolution

of fMRI. fMRI learning let exact location of brain activity and some groundbreaking study illustrate remarkable

similarities in the language-responsive structures in infants and adults. [82], [83].

4.1.3 Electroencephalography (EEG) is an electrophysiologic monitoring technique designed to capture brain

electrical activity. This is characteristically non-intrusive, with the electrodes located around the scalp, but, as in

electrocorticography, intrusive electrodes are sometimes used. EEG tests changes in voltage arising from ionic

current inside brain neurons. In clinical contexts, EEG mentions the monitoring over a period of time of the

normal electrical activity of the brain, as reported from multiple electrodes mounted on the scalp[84].

4.1.4 Event-related Potentials (ERPs) have been commonly used in infants and young children to study speech

and language production. ERPs, a part of the EEG, represent electrical activity that is time-locked to present a

particular sensory stimulus (for example, syllables or words) or a cognitive process (recognition within a

sentence or phrase of a semantic violation)[85]. By placing sensors on a child's scalp, it is possible to quantify

the behavior of neural networks firing in a synchronized and synchronous manner in open field environments,

and to detect voltage shifts that occur as a result of cortical neural activity[86],[87].

4.1.5 Magnetoencephalography (MEG) Is another method for brain imaging which tracks exquisite temporal

resolution of brain activity. The SQUID sensors positioned within the MEG helmet evaluate the minute

magnetic fields associated with electrical currents generated by the brain while performing sensory, motor, or

cognitive tasks. MEG facilitates the exact location of the neural currents accountable for magnetic field

sources[88],[89] the use of modern head monitoring methods and MEG to illustrate phonetic recognition in

newborns and infants in their first year of life..

4.1.6 Near-Infrared Spectroscopy (NIRS) Cerebral hemodynamic responses to neuronal activity are also

measured, but light absorption sensitive to haemoglobin concentration is used to assess activation [90]. NIRS

monitors increases in concentrations of blood oxy- and deoxy-haemoglobin in the brain, as well as increases in

total blood volume in various areas of the cerebral cortex using near-infrared light. The NIRS system can assess

activity in different brain regions by constantly monitoring the amount of haemoglobin in blood. In the first two

years of life, studies have started to surface on children, testing infant responses to phonemes as well as longer

periods of speech such as "motherese" and forward versus reversed sentences.

4.1.7 Diffusion Tensor Imaging (DTI) is an MRI-based neuroimaging technique that allows an estimation of

the position, orientation, and anisotropy of the white matter tracts of the brain [91].

4.1.8 Positron emission tomography (PET) tests pollutants from metabolically active chemicals injected into the

bloodstream, which are radioactively labeled. The emission data is processed by a computer to generate multi-

dimensional images of the distribution of the chemicals around the brain [92].

4.2 Data Analysis

Functional magnetic resonance imaging (fMRI) is a safe and non-invasive way of measuring brain function by

using brain activity-related signal changes. The method has become an omnipresent instrument of fundamental,

clinical, and cognitive neuroscience. This approach will calculate little changes in metabolism occurring in the

active part of the brain. We analyze the fMRI data in order to identify the parts of the brain that are involved in a

function, or to determine the changes that occur due to brain lesion in brain activities.

4.2.1 Statistical Analysis Methods

The efficiency of the fMR images is enhanced during the preprocessing stages. Thereafter, statistical analysis is

attempted to establish which voxels the stimulus stimulates. Many of the fMRI studies are focused on the

association between the hemodynamic response process and stimulation. Activation determines the changes in

the images to local severity. These methods can be divided into two specific categories: univariate methods

(methods for testing hypotheses), and multivariate methods (methods of exploration).

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