N170 changes reflect competition between faces and identifiable characters during early visual processing

According to the neuronal recycling hypothesis, brain circuits can gain new functions through cultural learning, which are distinct from their evolutionarily established functions, creating competition between processes such as facial and identifiable character processing. In the present study, event-related potential (ERP) recording was used to examine electrophysiological correlates of identification levels of Chinese characters as well as the competition between facial and Chinese character processing after the characters were learnt. Twenty volunteers performed a lateralized face detection task, and N170 responses were recorded when the participants viewed only Chinese characters (identifiable or unidentifiable in Xiaozhuan font), or Chinese characters and faces concurrently. Viewing identifiable Chinese characters bilaterally elicited larger N170 amplitudes than viewing unidentifiable ones. N170 amplitudes in response to faces bilaterally declined when identifiable Chinese characters and faces were viewed concurrently as compared to viewing unidentifiable Chinese characters and faces concurrently. These results indicate that the N170 component is modulated by the observer's identification level of Chinese characters, and that identifiable Chinese characters compete with faces during early visual processing.