Disentangling lexical processing and familiarity processing during visual word recognition

The lexical processing of visual words is usually reflected by the difference in brain activation between words and pseudowords (or high-frequency and low-frequency words) at approximately 250 ms in the ventral occipitotemporal cortex. However, because orthographic forms of words (or high-frequency words) are visually more familiar than pseudowords (or low-frequency words), we questioned whether the corresponding results reflected lexical processing (lexicality hypothesis) or visual familiarity processing (familiarity hypothesis). In the present study, event-related potentials (ERPs) were elicited by Chinese components. The lexicality (lexical and non-lexical) and component frequency (high and low) of the components were orthogonally manipulated. Component frequency refers to how often a component is seen in daily life and can index visual familiarity. An implicit reading task (color decision task) was performed. Participants were asked to determine the color of each stimulus. The results showed that component frequency, rather than lexicality, significantly modulated the ERP amplitude at ~250 ms in the parietooccipital scalp region, supporting the familiarity hypothesis. Source analysis results suggest that the fusiform gyrus is the neural origin of visual familiarity processing. In contrast, lexical processing was reflected by the N170 peak latency difference. The N170 elicited by lexical components peaked significantly earlier than it did when elicited by non-lexical components. The dissociation of lexical and visual familiarity processing has significant implications for the neural mechanisms underlying visual word recognition.

Grand-averaged event-related potentials (ERPs) at electrodes PO7 and PO8.

Mass univariate analysis

Source analysis results

Experimental stimulus and procedure