Holistic Integration in the Processing of Chinese Characters as Revealed by Electroencephalography Frequency Tagging

Abstract

It is debated whether perceptual expertise of nonface objects, such as visual words, is indicated by holistic processing, which is regarded as a marker of perceptual expertise of faces. We address this question by frequency-tagged electroencephalography. Different parts of real or pseudo Chinese characters are presented at distinctive frequencies (6 or 7.2 Hz), which induce frequency-tagged steady-state visual-evoked potentials at occipital brain areas. The intermodulation response (e.g., 6 + 7.2 = 13.2 Hz) would emerge when holistic integration takes place. Our results suggest that the intermodulation response to the real characters is left lateralized, which is contralateral to previous findings with faces. Furthermore, at the left occipital area, the intermodulation response to real characters is more prominent than pseudo characters, suggesting that holistic integration is enhanced for real characters than for pseudo ones. Taken together, our findings suggest that holistic integration is potentially a general expertise marker for both faces and non-face objects.

Orthographic deficits but typical visual perceptual processing in Chinese adults with reading disability

“…The frequency-tagged SSVEPs study revealed normal visual binding in adults with RD as in typical controls (Cai et al, 2020), suggesting intact visual holistic processing. We also found that Chinese characters elicited greater intermodulation response than pseudo characters in adults with RD, which is also consistent with typical controls.…”

“…Specifically, signal-to-noise ratio (SNR) in SSVEP responses was used for further analysis. It was defined as the ratio of SSVEP response at a given frequency to its SSVEP responses at its nearby frequencies (Cai et al, 2020).…”

“…Frequency-tagged SSVEPs was conducted with two parts of the visually presented object displayed at different frequencies (for example, one part flickered at f1, another at f2), and the intermodulation frequency (f1+f2) was measured as the neural signature of holistic integration. Previous study has demonstrated intermodulation frequency in typical Chinese adults using Chinese characters (Cai et al, 2020), and it was greater than that using pseudo-characters, suggesting greater holistic integration for real characters.…”

Intermodulation from Unisensory to Multisensory Perception: A Review

“…For example, Cai et al [ 12 ] used the IM-based steady-state visual-evoked potential (SSVEP) technique to study the integration of Chinese characters. In the experiment, participants needed to look at the real characters or fake characters with symmetrical structures flashing on the computer screen.…”

“…Second-order IMs are considered low-order neural interactions [ 12 ]. As this experiment showed, second-order IMs may represent low-level bottom-up cognitive processing, in which participants passively perceived the flickering free from any expectations or focused attention.…”