Chinese character recognition in mirror reading: evidence from event-related potential

As is well known, mirror reading in language requires recognition of words and letters in mirror-reversed pattern compared with normal reading, and the cognitive mechanism underlying the mirror reading may involve two critical processes: visuospatial transformation and linguistic regulation. Chinese characters, different from English, are characterized by some unique features in orthography and spelling. Using ERP techniques, the present study investigated neural correlates underlying the mirror reading of Chinese characters, and whether the cognitive processes underlying the recognition of mirrored Chinese characters is different from those of alphabetic words. Twelve native Chinese speakers participated in the experiment, during which they were instructed to make an animal/nonanimal distinction. The stimuli varied with the word category (animal vs nonanimal) and presentation format (normal vs mirror-reversed). The data analyses focused on three aspects: the reaction times (RT) for Chinese words of normal and mirror-reversed formats, peak latencies, and peak amplitudes of ERP components elicited by mirror-reversed and normal Chinese words. The results from implicit reading provide evidence for a mirror-reversed effect. The behavioural data showed that mirror-reversed words were more difficult to identify than normal words, with RTs delayed for mirror-reversed words over normal words. Moreover, a clear N2 component, with maximal activity occurring at 200-250ms interval (N2), was more negative for mirror-reversed words than for normal words at posterior regions. However, there were no latency differences between normal and mirror-reversed words. The occipital N2 might be closely related to abstract word form representation. Larger N2 amplitude in response to mirror-reversed Chinese words is interpreted as reflecting visuospatial transformation in order to compensate for impaired word form analysis. The result of no N2 latency delay indicated that word form analysis and visuospatial transformation might be processed in parallel.