Akihiro Omote

表 昭治

表, 昭治

2993

9000392873782

Omote , Akihiro

Nishogakusha University Academic Repository / 二松学舎大学学術情報リポジトリ

（ARTICLES）Generalisation, Modality, and Brain Plasticity: The Three Fundamental Concepts of Neuroimaging in Language StudiesAkihiro Omote−−INTRODUCTIONSince the advent of CT scanning technology in the 1970s, neuroimaging has increased refinement and contribution to cognitive science and language learning in adults and children with various in vivo monitoring techniques. Among those methods were positron emission tomography (PET), functional magnetic resonance imaging (fMRI), electroencephalography/ event-related potential (EEG/ERP), and magneto-encephalography (MEG) (Neville & Bavelier, 1998). The contribution should be, on the one hand, due to our improvement of psychological knowledge, and on the other, due substantially to the applied computational technology using mass brain data (Churchland, & Sejnowski, 1998).Among many neuroimaging techniques, PET, EEG, and fMRI have frequently been used as robust methodologies in the articles of cognitive neuroscience and are contributive to the advancement of language study from the early onset to the new stage of neuroimaging.This shor t essay focused on three fundamental concepts (generalisation, modality, and brain plasticity) reviewed from early works in Neville & Bavelier’s (1998) or Pinel’s (2005). The strategy to extract those keys was to start to trace history back to the solid rationale of neuroimaging. This is to elicit pivotal points familiar to potential advantage and disadvantage for studies of language (phonology, syntax, and semantics), and to get a highlight for a new bridge (Bruer, 1997) between neuroscience and language learning studies.GENERALISATIONPinel (2005) maintained that neuroimaging catalysed a fundamental breakthrough for neurobiology not only by the new methodology but also by generalisable and replicable characteristics of science. For example, a classical neuro-linguistic model, the Wernicke- Geschwind Model (Geschwind, 1970), emphasised the fixed roles of three cerebral regions that originated with retrospective brain damage study (i.e., Broca’s area in the inferior frontal lobe [B], Wernicke’s area between the superior temporal and the parietal lobes [W], and the arcuate 国際政経論集（二松學舍大学）第 24 号，208 年３月−2−fasciculus [A] which connects Wernicke’s to Broca’s area [see Figure 1]). The model posited left-cortical localisation of language. However, there was a lack of sufficient evidence, so this model was for a long time the subject of criticism (Pinel, 2005).Figure 1 The Wernicke-Geschwind Model (Geschwind, 1970).Because the model grew out of aphasiology that used the unreplicable and invasive treatment such as sodium amytal test (Wada, 1949), or commissurotomy (Gazzaniga & Sperry, 1967), it was somewhat hard to apply it as a tenable theory to general contexts. In contrast, generalisability and prospectivity have been the most advantageous feature of neuroimaging approach since it allows us to extend the investigation into a broad linguistic function with healthy subjects and more general population (including even infant study). This advantage went with some non-invasive or relatively less invasive techniques (Dick et al., 2014; Neville & Bavelier, 1998; Pinel, 2005). Table 1 shows some of the cognitive neuroscience methods used in language studies.Table 1 Different methods used in cognitive neuroscience and language studiesMethod	 Type	 Invasiveness	 Participants	 Brain	property	usedEEG/ERP Recording Non-invasive Adult/Children ElectricalSingle-cell/multi-unit recordings Recording Invasive Adult ElectricalTMS Stimulation Non-invasive Adult/Children ElectromagneticMEG Recording Non-invasive Adult/Children MagneticPET Recording Invasive Adult HemodynamicfMRI Recording Non-invasive Adult/Children HemodynamicNote: TMS refers to transcranial magnetic stimulator.From the 1980s to this date, positron emission tomography (PET) was one of the innovative technologies for linguistic-localisation study (Damazio, Grabowski, Tranel, Hichiwa, Generalisation, Modality, and Brain Plasticity: The Three Fundamental Concepts of Neuroimaging in Language Studies（表）−−Damazio, 1996; Peppel, 1996; Petersen, Fox, Posner, & Raichle, 1988). Petersen et al. (1988), for example, used PET to investigate the cortical anatomy of semantic and phonological processing. They measured the amount of blood flow to various parts of the single-word processing. The significant advantage of their study was that Petersen and his colleagues used injections of the radioactive water intravenously, rather than into carotid artery (Pinel, 2005) so that they could explore both hemispheres simultaneously in relatively long duration (10 minutes per one test). This study then revealed that audio- and visually- induced activations occurred extendedly along the central fissures of both hemispheres. Thus, this was a good exemplification of neuroimaging technique that reached a compelling conclusion beyond the Wernicke-Geschwind Model and the relevant theories of left- localisation. However, we should be careful about those results because it did not necessarily dispute two hemispheres’ independent functions and different capacities integrated by the cerebral commissures. In fact, the study contributed to further understanding of split-brain research related to language and its functions (Beenman, & Chiarello, 1998; Pinel, 2005).Adapted from Churchland and Sejnowski (1988)Figure 2 Diverse modality of neuroscience techniquesMODALITYOne significant disadvantage of the neuroimaging technique is that a modality of spatial and temporal resolution we can choose is considerably diverse among different methods. This diversity (Figure 2) will affect directly or indirectly the availability of precisions for and ranges of measurement regarding experimental designs and contexts (Churchland, & Sejnowski, 1988). For example, Petersen et al.’s (1988) work would never have concluded without the sufficient −4−spatial resolution for detecting language-related functions scanning into a broader cortical area. It is notable for us that PET is not an easygoing (thus highly limited) method for researchers because it uses an invasive technique that needs radioactive water injection into subject’s body.Accordingly, regarding the noninvasiveness that is preferable to subjects’ protection, the functional magnetic resonance imaging (fMRI) study is more advantageous than PET (there are still risks for the high magnetism, though). Another beneficial aspect of fMRI is that it provides images of more distinct neuronal activities than PET due to the relatively higher spatial resolution (Churchland, & Sejnowski, 1998). For example, Bavelier et al. (1997) used fMRI technique to measure cerebral reading activity while monolingual healthy subjects read English sentences. Similar to the findings of Petersen et al. (1988), they revealed a pattern of small patches, not well-circumscribed centres suggested by Wernicke- Geschwind Model.Electroencephalography (EEG) is another noninvasive technique, which has long provided us with an excellent online psychophysiological advantage with high temporal resolution for millisecond-by-millisecond record of electrical brain activity. Osterhout, McLaughlin, & Bersick (1997), for example, using event-related potentials (ERPs) known as continuous and multi-dimensional recording technique for the electrical brain activities of interest, separated the distinct minute temporal patterns of a syntactic (sentence form) process from those of semantic (sentence meaning) processes. Specifically, researchers define N400, as a negative-going wave that peaks at about 400 milliseconds in response to semantically inappropriate words (e.g., The cats won’t BAKE). On the other hand, P600 is a positive-going wave that peaks at about 600 milliseconds responding to structure anomalies (e.g., The cats won’t EATING...). Importantly, they elicited both N400 and P600 effects simultaneously (within 200 milliseconds) when subjects are reading sentences involved with both anomalies (e.g., The cats won’t BAKING), which strongly implied fundamental sub-processes that were not serial but was nearly parallel. This finding apparently contradicted the hypothesis of Wernicke-Geschwind Model that posited a linear (strictly serial) process of phonological phase followed by grammatical phase.BRAIN	PLASTICITYERP applied in language study revealed clinical evidence for the cerebral plasticity and regional reconstruction (Bavelier et al., 1997). In fact, it has provided a robust approach for aphasic patients or signers’ linguistic reorganisation in the cognitive aftermath of the brain disorder and the following training (Thomas et al., 1997; Corina, 1998). Thomas et al. (1997), for example, documented shifts in language lateralisation after recovery from aphasia in adults, which suggested a new hypothesis that human brain under certain circumstances is changeable enough to undergo irregular updating in cerebral activities including language and language behaviour. However, very little is known about the neural substrates of the phenomenon (Neville, & Bavelier, 1998).More recently, incipient plasticity study on healthy subjects has also been establishing credible evidence as well as a new challenge for infant language development (Dick et al., Generalisation, Modality, and Brain Plasticity: The Three Fundamental Concepts of Neuroimaging in Language Studies（表）−−2014; Garcia-Sierra et al., 2011; Wang, Kuhl, Chen, & Dong, 2009). Garcia-Sierra et al. (2011), for example, obtaining ERPs comparing Spanish-English bilingual children with monolingual children within a longitudinal and cross-sectional framework, found that bilingual infants’ brain responses to speech differ from the pattern of monolingual infants’.The implication was that the early (up to 9 months) exposure to phonetic discriminatory responses related to the subsequent word production; bilinguals showed continuous improvement in neural discrimination of the phonetic units from Spanish and English with increasing age. However, as there seems to remain a significant unknown gap between the observed neural activation and our social behaviour, the possible implication is that research applied to language studies have been presenting enormous challenges to neuroscience and neuroimaging technique. CONCLUSIONThree fundamental concepts—generalisation, modality, and brain plasticity—were reviewed in the brief history of the neuroimaging technique. The ideas give various neuroimaging techniques a common framework to better understand the brain and language. Among them, PET, EEG, and fMRI have frequently been used as robust methodologies in the studies of language processing and language learning.Neuroimaging, such as PET or fMRI, has contributed empiricism and challenges by addressing the neural level of phonological and semantic processing, building on models of antecedent studies and a new understanding of constitutional networks; this helps to create perspectives on our future mind- and body behaviour. Applying combined neuroimaging methods can also help us reach optimal results toward the more precise language study.Despite the significant advances, however, further research is required to understand the social nature of language and language development, since language, especially when reading and writing, requires learning for people who live in a lifelong social context. In this respect, applied language studies in educational neuroscience have just started to identify how our brain is shaped to learn the first language or the additional foreign languages through language behaviour and experiences..ReferencesBavelier, D., Corina, D., Jessard, P., Padmanabhan, S., Clark, V. P., Karni, A., Pinster, A., Braun, A., Lalwani, A., Rauschecker, J. P., Turner, R., & Neville, H. (1997). Sentence reading: A functional MRI study at 4 Telsa. Journal of Cognitive Neuroscience, 9, 664-686.Beenman, M. J., & Chiarello, C. (1998). Complementary right- and left-hemisphere language comprehension. Current Directions in Psychological Science, 7, 2-8.Bruer, J. T. (1997) Education and the brain: A bridge too far. Educational Researcher, 26, 4- 16.Churchland, P., & Sejnowski, T. (1998). Perspectives on cognitive neuroscience. Science, 242, 741-745.Corina, D. P. (1998). Aphasia in users of signed languages. In P. Coppens, Y. Lebrun, & A. Basso (Eds.), Aphasia in atypical populations (pp. 261-310). New Jersey: Lawrence Erlbaum.−−Damazio, H., Grabowski, T.J., Tranel, D., Hichiwa, R. D., & Damazio, A. R. (1996). A neural basis for lexical retrieval. Nature, 380, 499-505.Dick, F., Lloyd-Fox, S., Blasi, A., Elwell, C., & Mills, D. (2015). Neuroimaging methods. In. D. Mareschal, B. Butterworth, A. Tolmie (Eds.), Educational Neuroscience. Oxford: Wiley-Blackwell.Garcia-Sierra, A., Rivera-Gaxiola, M., Percaccio, C. R., Conboy, B. T., Romo, H., Klarman, L., & Kuhl, P. K. (2011). Bilingual language learning: An ERP study relating early brain responses to speech, language input, and later word production. Journal of Phonetics, 39, 546-557.Gazzaniga, M. S., & Sperry, R. W. (1967). Language after section of the cerebral commissure. Brain, 90, 131-148.Geschwind, N. (1970). The organization of language and the brain. Science, 170, 940-944. Neville, H., Bavelier, D. (1998). Neural organization and plasticity of language. Current Opinion in Neurobiology, 8, 254-258.Osterhout, L., McLaughlin, J., & Bersick, M. (1997). Event-related brain potentials and human language. Trends in Cognitive Science, 1, 203-209.Petersen, S. E., Fox, P. T., Posner, M. M, & Raichle, M. E. (1988). Positron emission tomographic studies of the cortical anatomy of single-word processing. Nature, 331, 585-589.Pinel, J. P. J. (2005). Biopsychology 5th ed. Boston, MA: Allyn & Bacon.Thomas, C., Altenmuller, E., Marchmann, G., Kahrs, J., & Dichgans, J. (1997). Language processing in aphasia: changes in lateralization patterns during recover y reflect cerebral plasticity in adults. Electroencephalography and Clinical Neurophysiology, 102, 8697.Wada, J. A. (1949). A new method for the determination of the side of cerebral speech dominance. Igaku to Seibutsugaku, 14, 221-222.Wang, Y., Kuhl, P. K., Chen, C., & Dong, Q. (2009). Sustained and transient language control in the bilingual brain. NeuroImage, 47, 414-422.

Generalisation, Modality, and Brain Plasticity

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Generalisation, Modality, and Brain Plasticity

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