Cross-language Brain Activation Pattern Difference Between Chinese And English Verbal Fluency Task:an FNIRS Study

Verbal fluency describes how effectively people generate words and an index of human cognitive abilities. Verbal fluency test is used to assess the ability of extracting specific information with certain given rules therefore also an evaluation of memory and executive function. It can be not only used in clinical areas but also widely scientific researches and neuropsychological tests. With its good ecology functional Near Infrared Spectroscopy (referred fNIRS) is fit into the study of brain mechanism of verbal fluency and there are some preliminary results in Chinese verbal fluency task researches. Because different orthography and speech can cause different brain mechanisms in verbal fluency task. As a typical Logogram, Chinese has unique characteristics apart from other alphabetic writing. We hypothesized that these features may also mirror onto the brain mechanism of verbal fluency task, so Chinese fluency task may have its own unique pattern of neural activation. Therefore, the current study investigated language specific neural mechanism of verbal fluency task.This paper includes the two following studies:The purpose of the first research was to assess test-retest reliability of the fNIRS data of Chinese verbal fluency task. It was divided into two experiments. Experiment1probed the brain activation patterns when17right-handed graduate students doing Chinese verbal fluency task with LABNIRS fNIRS(made by Shimadzu co. Ltd). It was within-participants design. Participants were asked to complete the Chinese phonemic fluency task and Chinese category fluency task. The task sequence was randomized. Participants were measured by a44-channel probe set covering frontotemporal region. The dependent variable was the concentration of oxyhemoglobin (HbO) and the experimental task were divided into3blocks with60s of each block, during which30s was used for task period and the other30s for the rest. After one week, the second experiment began. The participants in experiment1went back again to repeat the test to measure test-retest reliability. The experimental task was the same as experimental one. The results showed that the reliability indices of Chinese category and phonem fluency tasks were0.74. Chinese category fluency task stably activated precentral gyrus, postcentral gyrus, middle frontal gyrus of the left hemisphere, precentral gyrus, postcentral gyrus of right hemisphere. Chinese phonemic fluency task stably activated precentral gyrus, postcentral gyrus, middle frontal gyrus, inferior frontal gyrus, supramarginal gyrus of the left hemisphere and precentral gyrus, postcentral gyrus of right hemisphere.The purpose of the study2was to detect brain activation pattern differences in verbal fluency task between Chinese-English and English-Chinese bilinguals. Research was divided into two experiments:Experiment3and4. Experiment3probed the brain activation patterns when20right-handed English major graduate students and senior students(English-Chinese bilinguals) doing Chinese and English verbal fluency tasks. The experimental design was the same as experiment1except the additional materials of the English phoneme and category fluency task. Four kinds of tasks were randomly presented to subjects. Experiment4probed the brain activation patterns when7right-handed Chinese-English bilinguals doing Chinese and English verbal fluency tasks to find meaningful neural features differences. Experimental design was the same as experimental3. The results showed that left supramarginal gyrus may be Chinese-specific brain activation areas of phonemic verbal fluency task.Under the conditions of this study, the following conclusions could be made:1. fNIRS can be used to detect Chinese verbal fluency task, with its high test-retest reliability on the categories and phonemic fluency tasks.2. The left supramarginal gyrus may be Chinese-specific brain activation areas of phonemic verbal fluency task. 3. Chinese category fluency task stably activated precentral gyrus, postcentral gyrus, middle frontal gyrus of the left hemisphere, precentral gyrus, postcentral gyrus of right hemisphere.4. Chinese phonemic fluency task stably activated precentral gyrus, postcentral gyrus, middle frontal gyrus, inferior frontal gyrus, supramarginal gyrus of the left hemisphere and precentral gyrus, postcentral gyrus of right hemisphere.