Visual Perceptual Features On Recognition Of Chinese Characters And Human Faces In Different Orientations

Word recognition and face recognition have important function in daily life of human society. To explore whether there is difference between them in terms of processing module and neural mechanism is one of the core problem of cognitive neural science. The present research adopted visual ERP technique to find out the visual perceptual features of the recognition of Chinese characters and human faces. Subjects are sixteen healthy right-handed university students. Stimuli are single Chinese characters and adult' s neutral faces presented in different orientations (upright orientation, inverted orientation, mirror image orientation and inverted mirror image orientation). The stimuli are randomized in equal frequency. The subjects are required to press different keys to the upright orientation and inverted orientation respectively (ignoring its mirror image). The EEG was recorded from 64 scalp locations. The results are as follows:In upright orientation, difference exists in N170 and LPC evoked by Chinese characters and human faces respectively. N170 elicited by human faces includes larger amplitude than that caused by Chinese characters, which suggests that the human visual could distinguish between faces and Chinese characters as early as 130 to 170ms. Whereas the right hemisphere has an advantage in the categorization of faces, Chinese characters are processed bilaterally. In the time window of 300 ms and 600 ms, faces evoke larger LPC than Chinese characters, which indicates that the categorization of stimuli don't end until the late stage of processing.In inverted orientation, only in the early stage of perceptual processing, human faces manifest its obvious orientation effect. Compared with upright human faces, inverted faces involve larger amplitude of P100, prolonged latency and larger amplitude of N170, which indicates that the inversion disrupts the early perceptual processing of human faces. However, Chinese characters are only affected by inversion in the late stage of processing. In the time window of 300 to 600 ms, inverted Chinese characters elicit a positive-going LPC, suggesting the recognition of inverted Chinese characters is related to mental rotation.In mirror orientation, mirror effects of Chinese characters are shown both in the early and late stage of perceptual processing significantly. Chinese characters in mirror orientation evoke larger amplitude of P100, prolonged latency and smaller amplitude of N170 than upright Chinese characters, indicating that the inversion disrupts the early perceptual processing of Chinese characters. In the time window of 300 ms to 500 ms, LPC caused by mirrored Chinese characters includes a negative-going brain wave, which reflects the similar processing for the inverted Chinese characters. Moreover, in the time window of 700 to 800 ms, the brain waves are inverted and separated, which indicates difference exists in processing between inverted Chinese characters and mirrored characters. However, face recognition isn't affected by the orientation of mirror.