ORIGINAL ARTICLE Neuroscience http://dx.doi.org/10.3346/jkms.2014.29.10.1416 • J Korean Med Sci 2014; 29: 1416-1424 Neural Substrates of Hanja (Logogram) and Hangul (Phonogram) Character Readings by Functional Magnetic Resonance Imaging Zang-Hee Cho,1 Nambeom Kim,1 The two basic scripts of the Korean writing system, Hanja (the logography of the traditional Sungbong Bae,2 Je-Geun Chi,1 Korean character) and Hangul (the more newer Korean alphabet), have been used together Chan-Woong Park,1 Seiji Ogawa,1,3 since the 14th century. While Hanja character has its own morphemic base, Hangul being and Young-Bo Kim1 purely phonemic without morphemic base. These two, therefore, have substantially different outcomes as a language as well as different neural responses. Based on these 1Neuroscience Research Institute, Gachon University, Incheon, Korea; 2Department of linguistic differences between Hanja and Hangul, we have launched two studies; first was Psychology, Yeungnam University, Kyongsan, Korea; to find differences in cortical activation when it is stimulated by Hanja and Hangul reading 3Kansei Fukushi Research Institute, Tohoku Fukushi to support the much discussed dual-route hypothesis of logographic and phonological University, Sendai, Japan routes in the brain by fMRI (Experiment 1). The second objective was to evaluate how Received: 14 February 2014 Hanja and Hangul affect comprehension, therefore, recognition memory, specifically the Accepted: 5 July 2014 effects of semantic transparency and morphemic clarity on memory consolidation and then related cortical activations, using functional magnetic resonance imaging (fMRI) Address for Correspondence: (Experiment 2). The first fMRI experiment indicated relatively large areas of the brain are Young-Bo Kim, MD Department of Neuroscience and Neurosurgery, Gachon activated by Hanja reading compared to Hangul reading. The second experiment, the University, 21 Namdong-daero 774beon-gil, Namdong-gu, recognition memory study, revealed two findings, that is there is only a small difference in Incheon 405-760, Korea Tel: +82.32-460-9033, Fax: +82.32-460-8230 recognition memory for semantic transparency, while for the morphemic clarity was much E-mail: [email protected] larger between Hanja and Hangul. That is the morphemic clarity has significantly more Funding: This research was supported by a grant (NRF-2006- effect than semantic transparency on recognition memory when studies by fMRI in 2005137 and NRF-2012M3A9B6055374) from by the Ministry correlation with behavioral study. of Science, ICT and Future Planning, Republic of Korea Government. Keywords: Neural Substrates of Language; Functional Magnetic Resonance Imaging; Functional Neuroimaging; Hanja and Hangul INTRODUCTION Ok” have several different meanings. On the other hand, its Hanja homologue, “美玉; Mee-Ok” has, in most cases, unique Hanja (the traditionally used logographic Korean character) and meaning. In case of Hangul, because the first character “미” (mi) Hangul (the more recent phonological Korean character) are the could be multiples of morphemes, for example, “美” (mi, “beau- two basic scripts that have been used in Korea for the last five tiful”), “米” (mi, “rice”), and “微” (mi, “small”). A similar argu- hundred yr. Hanja has complex and irregular nature in writing, ment can be applied for the second constituent “옥.” (2). In ad- spelling and pronunciation, but each character or word that is dition to morphemic clarity, semantic transparency is the second made by one or more characters has strong and clear morphe- significant characteristic in the language processing of the word, mic information. Hangul, on the other hand, has regular and log- whether the word is in Hanja or Hangul. In Hanja words, which ical composition in writing, therefore, clear spelling and pronun- make up over 70% of the entire Korean vocabulary, are predomi- ciation, but, without strong morphemic information (1). Apart nantly compound words composed of two or more constituent from these linguistic property, Hanja and Hangul have different morphemes, however, both have variable semantic transparen- semantic divergence. Therefore, a morpheme written in Hangul cy. If the compound word has high semantic transparency (HT), alone could represent several different meanings, i.e., morphe- the meaning of the compound word can be better understood mically different context, that is Hangul has low morphemic clar- and comprehended (3-6). ity (LMC). Whereas, in most cases, each Hanja has unique mean- Based on these linguistic differences between Hanja and ing, that is it has high morphemic clarity (HMC). In short, the Hangul, we have attempted to localize the brain regions that are Hangul script has significantly more homonym than Hanja. For differentially activated according to the logogram and phono- instance, “beautiful jade” written in Hangul could be “미옥; Mee- gram and evaluated the effect of semantic transparency and the © 2014 The Korean Academy of Medical Sciences. pISSN 1011-8934 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. eISSN 1598-6357 Cho Z-H, et al. • Neural Involvement of Logographic Script Processing morphemic clarity on the Hanja and Hangul with respect to rec- graphic characters like Hanja are sent to the forebrain area via the ognition memory. It is interesting to note that, in respect to lan- left superior parietal cortex (LSPC; BA7), then to Broca’s area guage system, Korean language has unique and interesting (BA45) where the input is translated or transformed and forward- properties which could provide an excellent opportunity for un- ed to motor related speech areas, Broca’s area (BA44 or 45), for derstanding neural involvement of language processing. speech preparation and then to the premotor areas (BA 4 or 6) for To build a possible neural supporting bases of present study, the induction of mouth movement to allow for word production we have illustrated a conceptual and hypothetical functional dia- (13). This dual-route hypothesis appears to be the interesting gram of the brain (2, 7-9) in Fig. 1. When a script is seen by the eyes neural circuitry for the explanation of language processing, and it activates the primary visual cortex (V1; Brodmann’s area can be adopted, especially, for the Hangul and Hanja study in [BA]17). This information appears to be forwarded to the extrastri- brain (1). Another major pathway, still very little known, is the ate cortex (ESC; BA18, BA19, and BA37) where the image data is ventral pathway shown in the lower part of Fig. 1. The ventral analyzed and processed (10). For example, Hangul letters (graph- pathway consists of the inferior temporal cortex (BA37, 20, and eme) are forwarded to the angular gyrus (AG; BA39) where they 21), including the fusiform gyrus which will project to the hippo- are likely to be converted to sound language (phoneme) (7, 11), campus via the inferior longitudinal fasciculus (ILF) and inferior then to the Wernicke’s area (WA; BA22) where they are again con- fronto-occipital fasciculus (IFO). Functionally, this pathway is a verted into language to be understood and possibly stored (12). perception channel which could be involved in appreciation and Consequently, the information is forwarded to the Broca’s area memory rather than an action discussed above (10, 14) (see lower (BA44 and 45). Contrary to the phonological characters, the logo- pathway shown with red line in Fig. 1). Fig. 1. Neural hypothesis of the character processing of logographic and non-logographic languages. ILF, inferior longitudinal fasciculus; SLF, superior longitudinal fasciculus; IFO, inferior fronto-occipital fasciculus; SFO, superior fronto-occipital fasciculus. http://dx.doi.org/10.3346/jkms.2014.29.10.1416 http://jkms.org 1417 Cho Z-H, et al. • Neural Involvement of Logographic Script Processing MATERIALS AND METHODS (EPI) gradient echo sequence (TR/TE/α = 3,000 ms/28 ms/90°, slice thickness = 3 mm, in-plane resolution = 3×3 mm, 39 slices, Experiment 1: Comparison of fMRI based cortical field of view [FOV] = 192 mm, and matrix size = 64 × 64). Ninety activation study of Hangul and Hanja word readings images were acquired in each session (e.g., 30 sec Hanja, 30 sec Subjects baseline, and 30 sec Hangul). Two sessions were completed for Twelve native Koreans with high competency (HC) in Hanja each participant. Each subject’s anatomical image was also ac- (mean age = 28 yr; 6 males, 6 females; right-handed) participat- quired using a high resolution (1×1×1 mm), T1 weighted, and ed in the fMRI study. Written consent was obtained from all par- 3D gradient echo pulse sequence with magnetization prepared ticipants and the protocol was approved by the institutional re- rapid gradient echo (MPRAGE; TR/TE/TI = 1,770/2.93/900 ms). view board (IRB) of the Gachon Medical Center. The inclusion The total duration of the experiment for each subject was ap- criteria for HC was Hanja certification above grade 2 tested by proximately 30 min. Data was then analyzed using statistical the Korean Association for the Promotion of Hanja Education parametric mapping (SPM8; Wellcome Department of Cogni- (KAPHE) and writing or reading Hanja for a minimum of 2 yr in tive Neurology, London, UK) running under the Matlab 2008a daily life. (MathWorks, Sherbon, MA, USA). Functional volumes were re- aligned, co-registered to anatomical images, and normalized to fMRI paradigm the Montreal Neurological Institute (MNI) template using a A total of 150 of two-letter Hanja stimuli based on KAPHE guide- transformation matrix acquired from the T1 anatomical image lines equivalent to level 5 middle school education in Korea was normalization based on the SPM T1 template. Finally, spatial used. A total of 150 of the two-letter words most frequently used smoothing was performed with an 8 mm full width at half maxi- Hangul script items was also chosen to match the Hanja items.