Differential roles of spatial frequency on reading processes for ideograms and phonograms: A high-density ERP study

• Published in: Neuroscience research Vol. 72; no. 1; pp. 68 - 78
• Main Authors: Horie, Shizuka, Yamasaki, Takao, Okamoto, Tsuyoshi, Nakashima, Taisuke, Ogata, Katsuya, Tobimatsu, Shozo
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 2012
• Subjects: Adult; Brain - physiology; Evoked Potentials, Visual - physiology; Female; High spatial frequency (HSF); Humans; Japan; Japanese; Kana; Kanji; Language; Low spatial frequency (LSF); Male; Parallel visual pathways; Reading; Task Performance and Analysis; Visual Pathways - physiology; Japan; Parallel visual pathways; Reading; Kanji; Low spatial frequency (LSF); Kana; Japanese; High spatial frequency (HSF)
• ISSN: 0168-0102; 1872-8111; 1872-8111
• DOI: 10.1016/j.neures.2011.10.003

► Kanji and Kana are characterized by high- and low-spatial frequency (SF) information. ► SF contributed differentially to early visual ERP components between Kanji and Kana. ► Neural basis of Kanji and Kana reading partly results from their physical properties. The neural substrate of the dissociation between reading Japanese ideograms (Kanji) and phonograms (Kana) is currently unclear. To test whether spatial frequency (SF) information is responsible for this phenomenon, we recorded high-density event-related potentials (ERPs) with unfiltered or spatially filtered word stimuli in Japanese-speaking subjects. Kanji (early-learned, late-learned), Kana (word, non-word), and scrambled characters served as stimuli. Fourier analysis revealed that Kanji and Kana were characterized by high-SF (HSF) and low-SF (LSF) information, respectively. In ERPs with unfiltered stimuli, bilateral occipital P100, left occipitotemporal N170 and fronto-central N400 were elicited. Scrambled characters did not evoke left-lateralized N170 or clear N400. Under the LSF condition, P100 and N170 latencies for Kanji were significantly longer than those for Kana. In the HSF condition, P100 and N170 latencies for late-learned Kanji were significantly longer than those for early-learned Kanji. There was no significant difference in the N400 between Kanji and Kana in both SF conditions. These results suggest that early visual responses, but not the semantic component, are influenced by SF. This indicates a close link between Kana and LSF information, and between Kanji and HSF information. The differential effects of SF could underlie the neural basis of the differences between Kanji and Kana reading.