Effects of orthographic neighborhood on reading in Chinese An fMRI study

BACKGROUND： Much research has focused on neighborhood size in alphabetic languages. Results have consistently demonstrated that the neighborhood effect is a stimulating factor in word reading. The present study addressed whether there are neighborhood effects in Chinese character reading. OBJECTIVE： To investigate whether neighborhood effect exists in Chinese character reading and whether specific brain regions are responsible for it. DESIGN： An event-related design. SETTING： Beijing Anzhen Hospital. PARTICIPANTS： The experiment was conducted at Beijing Anzhen Hospital from October 2004 to December 2004. Undergraduate students, aged 19 24 years, were selected from Beijing Normal University, comprising 13 males and 16 females. Inclusive criteria： ① Neurologically normal and right-handed; ② native-Chinese speakers. All subjects gave informed consent prior to experimentation. METHODS： ① Behavioral experiment： the experiment utilized a 2 x 2 factorial design. The factors included orthographic neighborhood size （few or many neighbors） and lexical regularity （regular or irregular characters）. There was no significant difference between the ratio of regular and irregular characters in each family. The experiment was performed on a notebook PC and was piloted by E-Prime software. A fixation point ＂＋＂ was presented on the screen for 500 ms, and then the target item was displayed in the same place of the fixation for 2 000 ms. Subjects were asked to read the character aloud quickly and correctly. The target item disappeared once the subject read it. Reaction time （RT） and error ratios were collected and analyzed. ② fMRI study： the study was an event-related design. Each character was presented for 500 ms, and the offset was followed by ＂＋＂ presented for 1 500 - 26 000 ms. Each duration was divided by 500 exactly. The subject was required to read silently. AFNI software package was used to analyze the fMRI data. MAIN OUTCOME MEASURES： ① RT and error ratio in behavioral experiment; ② Brain mapping in fMRI study. RESULTS： Twenty-nine undergraduate students were involved in the result analysis. ① Behavioral experiment results of RT： the main effect of regularity was highly significant for participants （F1） and items （F2） [F1 （1,28） = 135.74, P 〈 0.01; F2 （1,76） = 49.506, P 〈 0.01], with regular words being responded faster than irregular words. The main effect of N was not significant, but was localized in an uncertain area [F1 （1,28） = 3.182, P 〉 0.05; F2 not significant]. Moreover, there was an interaction between neighborhood and regularity [F1 （1,28） = 6.666, P 〈 0.05; F2 （1 ,76） = 3.157, P 〉 0.05]. Analyses of simple effect determined that when the characters were irregular, the RT of low neighborhoods was shorter than high neighborhoods. Behavioral experiment results of error ratio： similar analyses were performed on the number of errors in the naming task. ANOVA demonstrated a main effect of regularity [F1 （1,28） = 10.475, P 〈 0.01; F2 （1,76） = 4.686, P 〈 0.05], with errors of regular words less than irregular words. The main effect of neighborhoods was not significant. Moreover, there was an interaction between neighborhood and regularity by subjects [F1 （1,28） = 7.632, P 〈 0.05], but not by items [F2 （1,76） =3.906, P 〉 0.05]. Analyses of simple effect found that when the characters were regular, the number of errors in high neighborhoods （23%） was greater than in low neighborhoods （11%）. ② fMRI results： bilateral fusiforms were sensitive to Chinese character shape. Both neighborhoods effect and regular effect mainly yielded right cerebral hemisphere and bilateral brain area. CONCLUSION： Neighborhood effect existed in character reading. However, results are contrary to what has been shown in English word reading. The fewer neighborhoods that one character had, the shorter the RT was. The fMRI results demonstrated the neighborhood effect and regular effect primarily stimulated right cerebral hemisphere and the bilateral brain area.