The neurophysiology of visual word recognition : is the N170 component a marker of orthographic or phonological sensitivity?

Abstract

The N170 ERP component is frequently associated with visual word expertise. However, studies have also argued that due to the intimate orthography-to-phonology mapping in alphabetic scripts, the N170 is also an index of phonological access. Capitalizing on the arbitrary orthography-to-phonology mapping property of Chinese characters, this study aimed to tease apart whether the N170 component is modulated by the orthographic form or also automatically co-activates the corresponding phonological forms of a character. 25 right-handed native Cantonese speakers participated in a lexical decision task and (homophone or visual) matching judgment task. Stimuli consisted of lexical forms including random stroke combinations, non characters, pseudo characters and real characters. The real characters also varied in phonological regularity and consistency. ERP results revealed that all orthographic conditions (i.e. real, pseudo and non characters) elicited a greater N170 component than random stroke combinations regardless of task, suggesting that the N170 is responsive to word-like stimuli during orthographic processing. However, regularity and consistency effects were only found in the matching judgment task, suggesting that orthography-to-phonology mappings might be activated when phonology is explicitly demanded. These results indicate that orthographic processing is automatic at the N170 component, but phonological processing may not necessarily be engaged in Chinese.