Similarities and differences betweenChinese and English word processing unveiled by MEG

Ying Liu14, Erika J.C.L. Taylor24, Anto Bagic3, Charles A. Perfetti4

1 Department of Psychology, Liaoning Normal University 2 Department of Psychology and Center for the Neural Basis of Cognition, Carnegie Mellon University;

3 Department of Neurology, University of Pittsburgh4 Learning Research and Development Center, University of Pittsburgh

Acknowledgments

Research was in part supported by :

UPMC Center for Advanced Brain Magnetic Source Imaging (CABMSI)

Elekta-Neuromag Oy (Helsinki, Finalnd)

Abstract

A magnetoencephalography (MEG) experiment was conducted with Chinese-English bilinguals to investigate the brain mechanisms of Chinese and English word processing. Six participants who were native Chinese speakers and graduate students at the University of Pittsburgh were recruited to participate in the MEG study. A delayed naming task eliciting minimal movement requirement was performed, during which MEG signal was recorded. Word frequency was manipulated as an experimental factor. Participant data was spatially filtered using the Signal Space Separation (SSS) method, averaged by condition while time-locked to word presentation onset, and source localized using the Minimum Current Estimate (MCE) algorithm. Results are presented in terms of lateralization differences in occipital activation during Chinese and English reading, and further compared by word frequency. Additionally, comparisons of brain networks supporting Chinese and English word reading will be explored.

Occipital

Superior

Temporal

PreFrontal

And

Occipital

150 - 250 ms

250 - 350 ms

400 - 800 ms

Left hemisphere is elicited before Right,

however the Right hemisphere is the dominant source of activity.

Right hemisphere is elicited before Left,

however the Left hemisphere is the dominant source of activity.

CHINESE

ENGLISH

Reverse Pattern

Left hemisphere is the dominant source of activity.

Low Frequency words are processed in both hemispheres,

however Left hemisphere activation appears delayed.

Meaning Related

Activity in the Occipital area appears again at

a later time period (450 - 550 ms)..

CHINESE

Lots of activity in the Left PreFrontal area,

peaking at ~625 ms, but sustained over 400 - 800 ms.

ENGLISH

Task Related

Results 5

Occipital

Superior

Temporal

PreFrontal

And

Occipital

PreFrontal Occipital

~ 210 ms

~ 180 ms~ 210 ms

~ 180 ms

~ 330 ms

~ 330 ms

416 ms

482 ms

~ 330 ms

~ 330 ms

~ 330 ms

~ 330 ms

150 - 250 ms

250 - 350 ms

400 - 800 ms

Peak ~ 625 ms

L R

L R

Source Analysis 4

Introduction 1

Brain mapping studies have identified widely distributed brain networks that support the orthographic, phonological, and meaning processes associated with word reading. These areas include, among others, left occipital and occipito-temporal cortex, the left frontal operculum, bilateral primary motor cortex, superior and middle temporal cortex, and medial regions such as the supplementary motor area and anterior cingulate (Fiez and Petersen, 1998). An important question is the extent to which the identified areas are universal, supporting reading across very different writing systems, rather than specific to alphabetic writing.

Chinese provides a case of high contrast for alphabetic systems, because its graphic units, characters, do not represent phonemes, but rather morphemic (meaning-bearing) syllables. Nevertheless, behavioral studies lead to the conclusion that automatic activation of both meaning and pronunciation occurs in reading Chinese characters, as it does in English (Chua, 1999; Perfetti and Tan, 1998; Perfetti and Zhang, 1995; Xu et al., 1999; Zhang et al., 1999). Thus,despite the differences in their input units (radicals vs. letters) and their mapping functions (syllables vs. phonemes), Chinese and alphabetic systems of reading are similar at this general level, with important processing differences in details (Perfetti et al., 2002).

We used MEG recordings to study the reading of Chinese and English by Chinese and English bilinguals (native language Chinese, second language English). We used delayed naming, a task that (1) allows the examination of a single word reading event and (2) requires a specific reading process, namely the preparation of a spoken word form for reading out loud. This task assures that orthographic and phonological processes are engaged implicitly and may be detected in the 1,000 milliseconds prior to the signal to name the word. Furthermore, if MEG records are sensitive to word reading, then we should see a specific MEG indicator of a well-established word processing variable such as word frequency for both Chinese and English.

Analysis Procedures 3

6 native Chinese speakers TOEFL > 550

Elekta Neuromag

306 sensor Vectorview

Sampling Rate = 1000 kHz

Spatial Filtering

Signal Space Separation (SSS)

Frequency Filtering

Bandpass: 0.5 - 40 Hz

Rejection Parameters

Gradiometers: 3000 fT/cm

EOG: 150 µV

Averaging

Time-locked to onset of

presentation of word

Source Localization

Transformed all data to

standard head position

Localized sources using

Minimum Current Estimate (MCE)

Discussion 6

Early occipital activation patterns (and other reading network patterns not presented here) replicate results from an ERP experiment of the same task (Liu & Perfetti, 2003).

The left superior temporal region plays a supporting role in the task of reading, and is recruited later in the time course for low frequency words than for high frequency words. The active region may be related to access of word meaning, and so this could indicate a sluggish response in accessing words of increased difficulty.

Late in the time course (400 - 800 ms), we see that English words elicit PreFrontal activity while Chinese words elicit Occipital activity. This may be due to the task, which requires participants to hold a word in memory, mentally verbalizing for up to 1500 ms. During Chinese reading, occipital areas may be recruited for holding character patterns in visual memory, whereas executive functions may be recruited during tasks for which a person is less skilled, such as a Chinese speaker reading a second language.

Chua FK (1999): Phonological recoding in Chinese logograph recognition. J Exp Psychol Learn Mem Cogn 25:876–891.Fiez JA, Petersen SE (1998): Neuroimaing studies of word reading. Proc Natl Acad Sci U S A 95:914-921. Hamalainen, M., Hari, R., Ilmoniemi, R.J., Knuutila, J., & Lounasmaa, O.V. (1993). Magnetoencephalography - theory,

instrumentation, and applications to noninvasive studies of the working human brain. Reviews of Modern Physics, 65, 413-497

Kucera, Francis WN (1967): Computational analysis of present-day American English: Providence: Brown University Press.

Li G, Liu R, editors (1988): A dictionary of Chinese character information. Beijing: Science Press.Liu, Y., & Perfetti, C.A. (2003). The time course of brain activity in reading English and Chinese: An ERP Study of

Chinese Bilinguals. Human brain mapping, 18(3), 167-175.Perfetti CA, Liu Y, Tan LH (2002): How the mind meets the brain in reading: a comparative writing systems approach.

In: Kao HSR, Leong CK, Gao DG, editors. Cognitive neuroscience studies of the Chinese language. Hong Kong: Hong Kong University Press.

Perfetti CA, Tan LH (1998): The time course of graphic, phonological, and semantic activation in Chinese character identification. J Exp Psychol Learn Mem Cogn 24:101–118.

Perfetti CA, Zhang S (1995): Very early phonological activation in Chinese reading. J Exp Psychol Learn Mem Cogn 21:24 –33.

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Zhang S, Perfetti CA, Yang H (1999): Whole word, frequency general phonology in semantic processing of Chinese characters. J Exp Psychol Learn Mem Cogn 25:858–875.

References

Design 2

60 trials / condition

English: word length matched

Chinese: radical/stroke# matched

Delay Naming Task: 20% SPEAK trials

Chinese and English blocks (order counterbalanced)

Word Frequency randomized

Low FrequencyHigh Frequency

583.9 / million

136.1 / million

2.1 / million

1.2 / million

Chinese(Li & Liu, 1988)

English(Kucera & Francis, 1967)

long slim

Participants asked to mentally verbalize word until command to speak aloud.