N170 adaptation effect of the sub-lexical phonological and semantic processing in Chinese character reading

The event-related potential (ERP) studies have revealed a component (N170) near tempo-occipital electrodes was sensitive to visual words. However, its role in word reading is still controversial. A common view is that the N170 engaged in the visual/orthographic processing, whereas some evidence has shown the N170 involved in phonological and semantic processing. By taking advantage of the Chinese writing system's ideographic property, the current study directly examined whether the N170 was sensitive to the phonological and semantic processing in reading Chinese characters. Two ERP experiments were conducted in a neural adaption paradigm by manipulating the repetition of the sub-lexical phonetic/semantic radical. The ERP data were collected while participants performed a phonological judgment task on the 4th character after silently reading the four characters consecutively. The phonological similarity (Experiment 1) and semantic similarity (Experiment 2) were manipulated among the four characters. Experiment 1 examined the neural adaption of the four characters sharing the phonetic radical (e.g ), the character's pronunciation (e. g ), both of them (e. g ), or neither (e.g ) respectively. Experiment 2 examined the neural adaption of the four characters sharing the semantic radical (e. g ), the character's meaning (e.g ), both of them (e.g ), or neither (e.g) respectively. In both experiments, the results showed a significant neural adaption at N170 in all of the four conditions. The amplitude of the N170 observed in the 1st character decreased in the 2nd - 4th characters. In Experiment 1, the N170 neural adaptation at the left PO7 electrode was sensitive to the repetition of the phonetic radical, and the repetition of the character's pronunciation, but not to the repetition of both. These results indicated the left mid-fusiform gyrus might be sensitive to the visual/orthographic and phonological processing but not to the orthography-to-phonology mapping in Chinese character reading. In Experiment 2, the N170 neural adaption at the left PO7 electrode was only sensitive to the repetition of the character's meaning, which indicated the semantic processing might modulate the left N170 in character reading. The N170 neural adaption at the right PO8 electrode was sensitive to the repetition of the semantic radical and the character's meaning, which suggested that right N170 was involved in visual/orthographic and semantic processing in reading characters. In sum, the findings showed that the N170 was involved in the visual/orthographic processing and engaged in the phonological and semantic processing in Chinese character reading. Furthermore, the left N170 was sensitive to the character's phonological and semantic information, whereas the right N170 was sensitive to the character's meaning and its semantic radical.