Neural Representations of Typeface Tuning for Kanji Word Recognition

Adaptation to various typeface shapes is required to recognize words. However, how our visual word recognition system handles them is not fully understood. We investigated a distinct typeface tuning process that expresses the typeface structure embedded in a Japanese Kanji word to reduce shape variance across typefaces. We independently manipulated typeface structure (typeface-form) changes and word identity (word-form) changes and used fMRI with repetition suppression techniques to detect brain regions specific to changes in typeface-form and word-form. This study also investigated the effects of subjective typeface properties: exposure frequency and legibility on brain activity. The results indicated the following: 1) Regions responsive to the typeface-form were identified, with considerable repetition suppression in the bilateral middle fusiform gyrus (FuGs) during the sequential presentation of words in identical typefaces. 2) Regions responsive to word-form in the left ventral occipitotemporal cortex, right middle FuG, and hippocampus, which included typeface-form sensitive regions. These findings suggest that word appearance is tuned to the typeface-form by the concurrent two-type shape representations of each neural population involved in visual word processing. 3) No significant fMRI responses correlated with either typeface exposure frequency or legibility ratings, suggesting that regional activeness reflects objective typeface-forms rather than subjective perceptions.