Selectivity Of N170 For Visual Words In The Right Hemisphere:Evidence From Single-trial Analysis

Current progress in single trial analysis opens the gate for detecting single trial EEG data.It fully takes trial-by-trial variability of EEG epochs into consideration and thus provide more rich information compared to averaging N170.This thesis starts from selectivity of visual word N170 component,use single trial technique to investigate pattern of neural activity underlying early visual word processing for the first time.It especially focuses on role of right hemisphere.In Study 1,we compared selectivity of averaging N170 and single trial N170 amplitude.Event-related potential(ERP)studies typically demonstrate N170 selectivity for words in the left hemisphere,while neuroimaging and neuropsychological studies frequently show the involvement of right posterior brain region in the processing of visual words.Whereas a majority of N170 studies simply average EEG response to words across trials,it would be possible to miss some important information and obscure N170 difference.This study examined this possibility using single trial analysis.Results show that the selectivity of right hemisphere in visual word recognition,and further revealed larger latency variability across trials for words than stroke combinations in the right posterior brain region.In study 2,we combine single trial technique with cognitive measurements to explore the role of right posterior brain region in early word processing in the perspective of single trial level.Participants will be required to complete a lexical decision task on words and pseudowords and simultaneous EEG was recorded.We focused on latency variability in the right posterior brain region during visual word recognition in this study.Familiarity,word-likeness,confidence on pseudowords are rated to examine the cognitive correlates of latency variability.Results showed that the latency variability in right hemisphere is significantly correlated to rating scores of familiarity and word-likeness for pseudowords.Amplitude of averaging N170 in the right hemisphere is significantly correlated with reading ability.This revealed that right hemisphere has close relationship with knowledge of pseudoword in visual word processing and it play an important role in word recognition.In conclusion,using single trial analysis,this study reconstructed the selectivity of right hemisphere of the brain.We first observed higher trial-by-trial variability for visual words than stroke combinations in the right hemisphere and help explain the discrepancy between ERP study and other modalities.Furthermore,we discussed the latency variability of right hemisphere and cognitive measurements in visual word recognition and provide proof for the role of right hemisphere in early visual word processing.